[{"id":3682853,"web_url":"http://patchwork.ozlabs.org/comment/3682853/","msgid":"","list_archive_url":null,"date":"2026-04-27T17:58:51","subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","submitter":{"id":92516,"url":"http://patchwork.ozlabs.org/api/people/92516/","name":"Yury Norov","email":"ynorov@nvidia.com"},"content":"On Mon, Apr 27, 2026 at 07:13:48PM +0200, Christophe Leroy (CS GROUP) wrote:\n> At the time being, x86 and arm64 are missing unsafe_copy_from_user().\n\nNo, they don't. They (should) rely on a generic implementation from\nlinux/uaccess.h, like every other arch, except for PPC and RISCV.\n\nBut they #define arch_unsafe_get_user, and the unsafe_copy_from_user()\nbecomes undefined conditionally on that.\n\nSo please, fix that bug instead of introducing another arch flavor.\nWe'd always choose generic version, unless there's strong evidence\nthat arch one is better. \n\n\nThanks,\nYury\n \n> Add it.\n> \n> Signed-off-by: Christophe Leroy (CS GROUP) \n> ---\n> arch/x86/include/asm/uaccess.h | 29 ++++++++++++++++++++++++-----\n> 1 file changed, 24 insertions(+), 5 deletions(-)\n> \n> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h\n> index 3a0dd3c2b233..10c458ffa399 100644\n> --- a/arch/x86/include/asm/uaccess.h\n> +++ b/arch/x86/include/asm/uaccess.h\n> @@ -598,7 +598,7 @@ _label:\t\t\t\t\t\t\t\t\t\\\n> * We want the unsafe accessors to always be inlined and use\n> * the error labels - thus the macro games.\n> */\n> -#define unsafe_copy_loop(dst, src, len, type, label)\t\t\t\t\\\n> +#define unsafe_put_loop(dst, src, len, type, label)\t\t\t\t\\\n> \twhile (len >= sizeof(type)) {\t\t\t\t\t\t\\\n> \t\tunsafe_put_user(*(type *)(src),(type __user *)(dst),label);\t\\\n> \t\tdst += sizeof(type);\t\t\t\t\t\t\\\n> @@ -611,10 +611,29 @@ do {\t\t\t\t\t\t\t\t\t\\\n> \tchar __user *__ucu_dst = (_dst);\t\t\t\t\\\n> \tconst char *__ucu_src = (_src);\t\t\t\t\t\\\n> \tsize_t __ucu_len = (_len);\t\t\t\t\t\\\n> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);\t\\\n> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);\t\\\n> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);\t\\\n> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);\t\\\n> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);\t\\\n> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);\t\\\n> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);\t\\\n> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);\t\\\n> +} while (0)\n> +\n> +#define unsafe_get_loop(dst, src, len, type, label)\t\t\t\t\\\n> +\twhile (len >= sizeof(type)) {\t\t\t\t\t\t\\\n> +\t\tunsafe_get_user(*(type __user *)(src),(type *)(dst),label);\t\\\n> +\t\tdst += sizeof(type);\t\t\t\t\t\t\\\n> +\t\tsrc += sizeof(type);\t\t\t\t\t\t\\\n> +\t\tlen -= sizeof(type);\t\t\t\t\t\t\\\n> +\t}\n> +\n> +#define unsafe_copy_from_user(_dst,_src,_len,label)\t\t\t\\\n> +do {\t\t\t\t\t\t\t\t\t\\\n> +\tchar *__ucu_dst = (_dst);\t\t\t\t\t\\\n> +\tconst char __user *__ucu_src = (_src);\t\t\t\t\\\n> +\tsize_t __ucu_len = (_len);\t\t\t\t\t\\\n> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);\t\\\n> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);\t\\\n> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);\t\\\n> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);\t\\\n> } while (0)\n> \n> #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT\n> -- \n> 2.49.0\n>","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=wVLbC6mD;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=JEzvcYXQ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org;\n envelope-from=linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org;\n receiver=patchwork.ozlabs.org)","dkim=none (message not signed)\n header.d=none;dmarc=none action=none header.from=nvidia.com;"],"Received":["from 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The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: On Mon, Apr 27, 2026 at 07:13:48PM +0200, Christophe Leroy\n (CS GROUP) wrote: > At the time being,\n x86 and arm64 are missing unsafe_copy_from_user().\n No,\n they don't. They (should) rely on a generic implementation from linux/uaccess.h,\n like every other arch, except for PPC and RISCV.\n Content analysis details: (-2.1 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 SPF_PASS SPF: sender matches SPF record\n -0.0 SPF_HELO_PASS SPF: HELO matches SPF record\n -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from\n envelope-from domain\n -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from\n author's\n domain\n -0.1 DKIM_VALID Message has at least one valid DKIM or DK\n signature\n 0.1 DKIM_SIGNED Message has a DKIM or DK signature,\n not necessarily valid\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]\n -0.0 DKIMWL_WL_HIGH DKIMwl.org - High trust sender","X-BeenThere":"linux-snps-arc@lists.infradead.org","X-Mailman-Version":"2.1.34","Precedence":"list","List-Id":"Linux on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}},{"id":3682867,"web_url":"http://patchwork.ozlabs.org/comment/3682867/","msgid":"<63a4d0f6-0eb3-48cd-9f98-bf7b223b2606@kernel.org>","list_archive_url":null,"date":"2026-04-27T18:20:38","subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","submitter":{"id":92089,"url":"http://patchwork.ozlabs.org/api/people/92089/","name":"Christophe Leroy (CS GROUP)","email":"chleroy@kernel.org"},"content":"Le 27/04/2026 à 19:58, Yury Norov a écrit :\n> On Mon, Apr 27, 2026 at 07:13:48PM +0200, Christophe Leroy (CS GROUP) wrote:\n>> At the time being, x86 and arm64 are missing unsafe_copy_from_user().\n> \n> No, they don't. They (should) rely on a generic implementation from\n> linux/uaccess.h, like every other arch, except for PPC and RISCV.\n> \n> But they #define arch_unsafe_get_user, and the unsafe_copy_from_user()\n> becomes undefined conditionally on that.\n> \n> So please, fix that bug instead of introducing another arch flavor.\n> We'd always choose generic version, unless there's strong evidence\n> that arch one is better.\n\nBut they both implement the exact same unsafe_copy_to_user(). What is \nthe difference here ?\n\nShould that function become generic too ?\n\nChristophe\n\n> \n> \n> Thanks,\n> Yury\n> \n>> Add it.\n>>\n>> Signed-off-by: Christophe Leroy (CS GROUP) \n>> ---\n>> arch/x86/include/asm/uaccess.h | 29 ++++++++++++++++++++++++-----\n>> 1 file changed, 24 insertions(+), 5 deletions(-)\n>>\n>> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h\n>> index 3a0dd3c2b233..10c458ffa399 100644\n>> --- a/arch/x86/include/asm/uaccess.h\n>> +++ b/arch/x86/include/asm/uaccess.h\n>> @@ -598,7 +598,7 @@ _label:\t\t\t\t\t\t\t\t\t\\\n>> * We want the unsafe accessors to always be inlined and use\n>> * the error labels - thus the macro games.\n>> */\n>> -#define unsafe_copy_loop(dst, src, len, type, label)\t\t\t\t\\\n>> +#define unsafe_put_loop(dst, src, len, type, label)\t\t\t\t\\\n>> \twhile (len >= sizeof(type)) {\t\t\t\t\t\t\\\n>> \t\tunsafe_put_user(*(type *)(src),(type __user *)(dst),label);\t\\\n>> \t\tdst += sizeof(type);\t\t\t\t\t\t\\\n>> @@ -611,10 +611,29 @@ do {\t\t\t\t\t\t\t\t\t\\\n>> \tchar __user *__ucu_dst = (_dst);\t\t\t\t\\\n>> \tconst char *__ucu_src = (_src);\t\t\t\t\t\\\n>> \tsize_t __ucu_len = (_len);\t\t\t\t\t\\\n>> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);\t\\\n>> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);\t\\\n>> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);\t\\\n>> -\tunsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);\t\\\n>> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);\t\\\n>> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);\t\\\n>> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);\t\\\n>> +\tunsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);\t\\\n>> +} while (0)\n>> +\n>> +#define unsafe_get_loop(dst, src, len, type, label)\t\t\t\t\\\n>> +\twhile (len >= sizeof(type)) {\t\t\t\t\t\t\\\n>> +\t\tunsafe_get_user(*(type __user *)(src),(type *)(dst),label);\t\\\n>> +\t\tdst += sizeof(type);\t\t\t\t\t\t\\\n>> +\t\tsrc += sizeof(type);\t\t\t\t\t\t\\\n>> +\t\tlen -= sizeof(type);\t\t\t\t\t\t\\\n>> +\t}\n>> +\n>> +#define unsafe_copy_from_user(_dst,_src,_len,label)\t\t\t\\\n>> +do {\t\t\t\t\t\t\t\t\t\\\n>> +\tchar *__ucu_dst = (_dst);\t\t\t\t\t\\\n>> +\tconst char __user *__ucu_src = (_src);\t\t\t\t\\\n>> +\tsize_t __ucu_len = (_len);\t\t\t\t\t\\\n>> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);\t\\\n>> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);\t\\\n>> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);\t\\\n>> +\tunsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);\t\\\n>> } while (0)\n>> \n>> #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT\n>> -- \n>> 2.49.0\n>>","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass 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(--)","X-Spam-Report":"=?unknown-8bit?q?Spam_detection_software=2C_running_on_the_sy?=\n\t=?unknown-8bit?q?stem_=22bombadil=2Einfradead=2Eorg=22=2C?=\n\t=?unknown-8bit?q?_has_NOT_identified_this_incoming_email_as_spam=2E__The_ori?=\n\t=?unknown-8bit?q?ginal?=\n\t=?unknown-8bit?q?_message_has_been_attached_to_this_so_you_can_view_it_or_la?=\n\t=?unknown-8bit?q?bel?=\n\t=?unknown-8bit?q?_similar_future_email=2E__If_you_have_any_questions=2C_see?=\n\t=?unknown-8bit?q?_the_administrator_of_that_system_for_details=2E?=\n\t=?unknown-8bit?q?_?=\n\t=?unknown-8bit?q?_Content_preview=3A__Le_27/04/2026_=C3=A0_19=3A58=2C_Yury_N?=\n\t=?unknown-8bit?q?orov_a_=C3=A9crit_=3A_=3E_On_Mon=2C_Apr?=\n\t=?unknown-8bit?q?_27=2C_2026_at_07=3A13=3A48PM_+0200=2C_Christophe_Leroy_=28?=\n\t=?unknown-8bit?q?CS_GROUP=29_wrote=3A_=3E=3E_At_the?=\n\t=?unknown-8bit?b?IHRpbWUgYmVpbmcsIHg4NiBhbmQgYXJtNjQgYXJlIG1pc3NpbmcgdW5z?=\n\t=?unknown-8bit?b?YWZlX2NvcHlfZnJvbV91c2VyKCkuID4gWy4uLl0g?=\n\t=?unknown-8bit?q?_?=\n\t=?unknown-8bit?q?_Content_analysis_details=3A___=28-2=2E1_points=2C_5=2E0_re?=\n\t=?unknown-8bit?q?quired=29?=\n\t=?unknown-8bit?q?_?=\n\t=?unknown-8bit?q?_pts_rule_name______________description?=\n\t=?unknown-8bit?q?_----_----------------------_------------------------------?=\n\t=?unknown-8bit?q?--------------------?=\n\t=?unknown-8bit?q?_-0=2E0_SPF=5FPASS_______________SPF=3A_sender_matches_SPF_?=\n\t=?unknown-8bit?q?record?=\n\t=?unknown-8bit?q?_0=2E0_SPF=5FHELO=5FNONE__________SPF=3A_HELO_does_not_publ?=\n\t=?unknown-8bit?q?ish_an_SPF_Record?=\n\t=?unknown-8bit?q?_-0=2E1_DKIM=5FVALID=5FEF__________Message_has_a_valid_DKIM?=\n\t=?unknown-8bit?q?_or_DK_signature_from?=\n\t=?unknown-8bit?q?_envelope-from_domain?=\n\t=?unknown-8bit?q?_-0=2E1_DKIM=5FVALID=5FAU__________Message_has_a_valid_DKIM?=\n\t=?unknown-8bit?q?_or_DK_signature_from_author=27s?=\n\t=?unknown-8bit?q?_domain?=\n\t=?unknown-8bit?q?_-0=2E1_DKIM=5FVALID_____________Message_has_at_least_one_v?=\n\t=?unknown-8bit?q?alid_DKIM_or_DK_signature?=\n\t=?unknown-8bit?q?_0=2E1_DKIM=5FSIGNED____________Message_has_a_DKIM_or_DK_si?=\n\t=?unknown-8bit?q?gnature=2C_not_necessarily_valid?=\n\t=?unknown-8bit?q?_-1=2E9_BAYES=5F00_______________BODY=3A_Bayes_spam_probabi?=\n\t=?unknown-8bit?q?lity_is_0_to_1=25?=\n\t=?unknown-8bit?q?_=5Bscore=3A_0=2E0000=5D?=\n\t=?unknown-8bit?q?_-0=2E0_DKIMWL=5FWL=5FHIGH_________DKIMwl=2Eorg_-_High_trus?=\n\t=?unknown-8bit?q?t_sender?=","X-BeenThere":"linux-snps-arc@lists.infradead.org","X-Mailman-Version":"2.1.34","Precedence":"list","List-Id":"Linux on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Transfer-Encoding":"base64","Content-Type":"text/plain; charset=\"utf-8\"; Format=\"flowed\"","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}},{"id":3682903,"web_url":"http://patchwork.ozlabs.org/comment/3682903/","msgid":"","list_archive_url":null,"date":"2026-04-27T19:19:36","subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","submitter":{"id":92516,"url":"http://patchwork.ozlabs.org/api/people/92516/","name":"Yury Norov","email":"ynorov@nvidia.com"},"content":"On Mon, Apr 27, 2026 at 08:20:38PM +0200, Christophe Leroy (CS GROUP) wrote:\n> \n> \n> Le 27/04/2026 à 19:58, Yury Norov a écrit :\n> > On Mon, Apr 27, 2026 at 07:13:48PM +0200, Christophe Leroy (CS GROUP) wrote:\n> > > At the time being, x86 and arm64 are missing unsafe_copy_from_user().\n> > \n> > No, they don't. They (should) rely on a generic implementation from\n> > linux/uaccess.h, like every other arch, except for PPC and RISCV.\n> > \n> > But they #define arch_unsafe_get_user, and the unsafe_copy_from_user()\n> > becomes undefined conditionally on that.\n> > \n> > So please, fix that bug instead of introducing another arch flavor.\n> > We'd always choose generic version, unless there's strong evidence\n> > that arch one is better.\n> \n> But they both implement the exact same unsafe_copy_to_user(). What is the\n> difference here ?\n>\n> Should that function become generic too ?\n\nThis is what Linus said when added x86 implementation for copy_from_user()\nin c512c69187197:\n\n Note that it only does this [arch version] for the copying _to_ user space,\n and we still don't have a unsafe version of copy_from_user().\n \n That's partly because we have no current users of it, but also partly\n because the copy_from_user() case is slightly different and cannot\n efficiently be implemented in terms of a unsafe_get_user() loop (because\n gcc can't do asm goto with outputs).\n\nIn the unsafe_copy_to_user case, arch versions were justified. Just as\nsaid, I'm not against arch version for unsafe_copy_from_user(), but it\nshould be explained very well.","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=p6JtDZmM;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=YPchTHpL;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org;\n envelope-from=linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org;\n receiver=patchwork.ozlabs.org)","dkim=none (message not signed)\n header.d=none;dmarc=none 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linux-s390@vger.kernel.org,\n\tsparclinux@vger.kernel.org, linux-um@lists.infradead.org,\n\tdmaengine@vger.kernel.org, linux-efi@vger.kernel.org,\n\tlinux-fsi@lists.ozlabs.org, amd-gfx@lists.freedesktop.org,\n\tdri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,\n\tlinux-wpan@vger.kernel.org, netdev@vger.kernel.org,\n\tlinux-wireless@vger.kernel.org, linux-spi@vger.kernel.org,\n\tlinux-media@vger.kernel.org, linux-staging@lists.linux.dev,\n\tlinux-serial@vger.kernel.org, linux-usb@vger.kernel.org,\n\txen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org,\n\tocfs2-devel@lists.linux.dev, bpf@vger.kernel.org,\n\tkasan-dev@googlegroups.com, linux-mm@kvack.org,\n\tlinux-x25@vger.kernel.org, rust-for-linux@vger.kernel.org,\n\tlinux-sound@vger.kernel.org, sound-open-firmware@alsa-project.org,\n\tlinux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,\n\tloongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org,\n\tlinux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,\n\tlinux-sh@vger.kernel.org, linux-arch@vger.kernel.org","Subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","Message-ID":"","References":"\n <0ee46bb228d97163fbdc14f2a7c52b93d8bc34ce.1777306795.git.chleroy@kernel.org>\n \n <63a4d0f6-0eb3-48cd-9f98-bf7b223b2606@kernel.org>","Content-Disposition":"inline","In-Reply-To":"<63a4d0f6-0eb3-48cd-9f98-bf7b223b2606@kernel.org>","X-ClientProxiedBy":"BLAPR03CA0031.namprd03.prod.outlook.com\n (2603:10b6:208:32d::6) To CY8PR12MB8300.namprd12.prod.outlook.com\n (2603:10b6:930:7d::16)","MIME-Version":"1.0","X-MS-PublicTrafficType":"Email","X-MS-TrafficTypeDiagnostic":"CY8PR12MB8300:EE_|CY3PR12MB9678:EE_","X-MS-Office365-Filtering-Correlation-Id":"c742778b-fa9b-44f9-51b3-08dea491ed5d","X-MS-Exchange-SenderADCheck":"1","X-MS-Exchange-AntiSpam-Relay":"0","X-Microsoft-Antispam":"\n 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on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Type":"text/plain; charset=\"iso-8859-1\"","Content-Transfer-Encoding":"quoted-printable","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}},{"id":3683021,"web_url":"http://patchwork.ozlabs.org/comment/3683021/","msgid":"","list_archive_url":null,"date":"2026-04-27T21:52:05","subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","submitter":{"id":97,"url":"http://patchwork.ozlabs.org/api/people/97/","name":"Linus Torvalds","email":"torvalds@linux-foundation.org"},"content":"On Mon, 27 Apr 2026 at 12:19, Yury Norov wrote:\n>\n> This is what Linus said when added x86 implementation for copy_from_user()\n> in c512c69187197:\n\nNote that some things have happily changed in the six+ years since...\n\n> That's partly because we have no current users of it, but also partly\n> because the copy_from_user() case is slightly different and cannot\n> efficiently be implemented in terms of a unsafe_get_user() loop (because\n> gcc can't do asm goto with outputs).\n\nnow everybody can do asm goto with outputs.\n\nYes, it's disabled on older versions, so it's not *always* available,\nbut all modern versions do it. And if you care about performance, you\nwon't be using an old compiler.\n\n Linus","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=TU3pibDc;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org\n header.a=rsa-sha256 header.s=google header.b=CCbN7kZ3;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org;\n envelope-from=linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from bombadil.infradead.org (bombadil.infradead.org\n [IPv6:2607:7c80:54:3::133])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g4HXf05ZPz1xrS\n\tfor ; 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Mon, 27 Apr 2026\n 14:52:22 -0700 (PDT)"],"MIME-Version":"1.0","References":"\n <0ee46bb228d97163fbdc14f2a7c52b93d8bc34ce.1777306795.git.chleroy@kernel.org>\n <63a4d0f6-0eb3-48cd-9f98-bf7b223b2606@kernel.org>\n ","In-Reply-To":"","From":"Linus Torvalds ","Date":"Mon, 27 Apr 2026 14:52:05 -0700","X-Gmail-Original-Message-ID":"\n ","X-Gm-Features":"AVHnY4LQUFWo9ODz4M3q2vZC9Gn8nsdYr95Nd4ky5ERVHHxIyN_9ZXY5zjebfdc","Message-ID":"\n ","Subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","To":"Yury Norov ","Cc":"\"Christophe Leroy (CS GROUP)\" ,\n Andrew Morton ,\n\tDavid Laight ,\n Thomas Gleixner ,\n\tlinux-alpha@vger.kernel.org, Yury Norov ,\n\tlinux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org,\n\tlinux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,\n\tlinuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,\n\tlinux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,\n\tsparclinux@vger.kernel.org, linux-um@lists.infradead.org,\n\tdmaengine@vger.kernel.org, linux-efi@vger.kernel.org,\n\tlinux-fsi@lists.ozlabs.org, amd-gfx@lists.freedesktop.org,\n\tdri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,\n\tlinux-wpan@vger.kernel.org, netdev@vger.kernel.org,\n\tlinux-wireless@vger.kernel.org, linux-spi@vger.kernel.org,\n\tlinux-media@vger.kernel.org, linux-staging@lists.linux.dev,\n\tlinux-serial@vger.kernel.org, linux-usb@vger.kernel.org,\n\txen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org,\n\tocfs2-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com,\n\tlinux-mm@kvack.org, linux-x25@vger.kernel.org,\n rust-for-linux@vger.kernel.org,\n\tlinux-sound@vger.kernel.org, sound-open-firmware@alsa-project.org,\n\tlinux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,\n\tloongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org,\n\tlinux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,\n\tlinux-sh@vger.kernel.org, linux-arch@vger.kernel.org","X-CRM114-Version":"20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 ","X-CRM114-CacheID":"sfid-20260427_145925_960178_8FA9ED06 ","X-CRM114-Status":"GOOD ( 10.48 )","X-Spam-Score":"-1.8 (-)","X-Spam-Report":"Spam detection software,\n running on the system \"bombadil.infradead.org\",\n has NOT identified this incoming email as spam. The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: On Mon, 27 Apr 2026 at 12:19,\n Yury Norov \n wrote: > > This is what Linus said when added x86 implementation for\n copy_from_user()\n > in c512c69187197: Note that some things have happily changed in the six+\n years since...\n Content analysis details: (-1.8 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no\n trust\n [2a00:1450:4864:20:0:0:0:62c listed in]\n [list.dnswl.org]\n -0.0 SPF_PASS SPF: sender matches SPF record\n 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record\n -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from\n author's\n domain\n -0.1 DKIM_VALID Message has at least one valid DKIM or DK\n signature\n 0.1 DKIM_SIGNED Message has a DKIM or DK signature,\n not necessarily valid\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]\n 0.2 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail\n domains are different","X-BeenThere":"linux-snps-arc@lists.infradead.org","X-Mailman-Version":"2.1.34","Precedence":"list","List-Id":"Linux on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}},{"id":3683031,"web_url":"http://patchwork.ozlabs.org/comment/3683031/","msgid":"","list_archive_url":null,"date":"2026-04-27T22:30:16","subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","submitter":{"id":92516,"url":"http://patchwork.ozlabs.org/api/people/92516/","name":"Yury Norov","email":"ynorov@nvidia.com"},"content":"On Mon, Apr 27, 2026 at 02:52:05PM -0700, Linus Torvalds wrote:\n> On Mon, 27 Apr 2026 at 12:19, Yury Norov wrote:\n> >\n> > This is what Linus said when added x86 implementation for copy_from_user()\n> > in c512c69187197:\n> \n> Note that some things have happily changed in the six+ years since...\n> \n> > That's partly because we have no current users of it, but also partly\n> > because the copy_from_user() case is slightly different and cannot\n> > efficiently be implemented in terms of a unsafe_get_user() loop (because\n> > gcc can't do asm goto with outputs).\n> \n> now everybody can do asm goto with outputs.\n> \n> Yes, it's disabled on older versions, so it's not *always* available,\n> but all modern versions do it. And if you care about performance, you\n> won't be using an old compiler.\n\nThe minimal GCC version is 8.1, and asm goto with outputs is supported\nsince GCC-11. That would brake the build, if we just switch to using it\nwithout \"CC_IS_GCC && (GCC_VERSION >= 110100)\" guard.\n\nIs it worth to maintain 2 version of the function? I don't know...\n\nThanks,\nYury","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=PdZ5N2t+;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=nMn9Mg2e;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org;\n envelope-from=linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org;\n receiver=patchwork.ozlabs.org)","dkim=none (message not signed)\n header.d=none;dmarc=none action=none header.from=nvidia.com;"],"Received":["from bombadil.infradead.org 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linux-parisc@vger.kernel.org,\n\tlinux-sh@vger.kernel.org, linux-arch@vger.kernel.org","Subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","Message-ID":"","References":"\n <0ee46bb228d97163fbdc14f2a7c52b93d8bc34ce.1777306795.git.chleroy@kernel.org>\n \n <63a4d0f6-0eb3-48cd-9f98-bf7b223b2606@kernel.org>\n \n ","Content-Disposition":"inline","In-Reply-To":"\n ","X-ClientProxiedBy":"BN0PR04CA0197.namprd04.prod.outlook.com\n (2603:10b6:408:e9::22) To CY8PR12MB8300.namprd12.prod.outlook.com\n (2603:10b6:930:7d::16)","MIME-Version":"1.0","X-MS-PublicTrafficType":"Email","X-MS-TrafficTypeDiagnostic":"CY8PR12MB8300:EE_|SA1PR12MB6871:EE_","X-MS-Office365-Filtering-Correlation-Id":"1f3655ce-20ef-4e2c-2fe2-08dea4ac8fa5","X-MS-Exchange-SenderADCheck":"1","X-MS-Exchange-AntiSpam-Relay":"0","X-Microsoft-Antispam":"\n BCL:0;ARA:13230040|10070799003|376014|7416014|366016|1800799024|56012099003|22082099003|18002099003;","X-Microsoft-Antispam-Message-Info":"\n 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The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: On Mon, Apr 27, 2026 at 02:52:05PM -0700,\n Linus Torvalds wrote:\n > On Mon, 27 Apr 2026 at 12:19, Yury Norov wrote: > >\n > > This is what Linus said when added x86 implementation for [...]\n Content analysis details: (-2.1 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 SPF_PASS SPF: sender matches SPF record\n -0.0 SPF_HELO_PASS SPF: HELO matches SPF record\n -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from\n envelope-from domain\n -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from\n author's\n domain\n -0.1 DKIM_VALID Message has at least one valid DKIM or DK\n signature\n 0.1 DKIM_SIGNED Message has a DKIM or DK signature,\n not necessarily valid\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]\n -0.0 DKIMWL_WL_HIGH DKIMwl.org - High trust sender","X-BeenThere":"linux-snps-arc@lists.infradead.org","X-Mailman-Version":"2.1.34","Precedence":"list","List-Id":"Linux on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}},{"id":3683393,"web_url":"http://patchwork.ozlabs.org/comment/3683393/","msgid":"","list_archive_url":null,"date":"2026-04-28T11:20:17","subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","submitter":{"id":134,"url":"http://patchwork.ozlabs.org/api/people/134/","name":"Segher Boessenkool","email":"segher@kernel.crashing.org"},"content":"Hi!\n\nOn Mon, Apr 27, 2026 at 06:30:16PM -0400, Yury Norov wrote:\n> On Mon, Apr 27, 2026 at 02:52:05PM -0700, Linus Torvalds wrote:\n> > On Mon, 27 Apr 2026 at 12:19, Yury Norov wrote:\n> > >\n> > > This is what Linus said when added x86 implementation for copy_from_user()\n> > > in c512c69187197:\n> > \n> > Note that some things have happily changed in the six+ years since...\n> > \n> > > That's partly because we have no current users of it, but also partly\n> > > because the copy_from_user() case is slightly different and cannot\n> > > efficiently be implemented in terms of a unsafe_get_user() loop (because\n> > > gcc can't do asm goto with outputs).\n> > \n> > now everybody can do asm goto with outputs.\n> > \n> > Yes, it's disabled on older versions, so it's not *always* available,\n> > but all modern versions do it. And if you care about performance, you\n> > won't be using an old compiler.\n> \n> The minimal GCC version is 8.1, and asm goto with outputs is supported\n> since GCC-11. That would brake the build, if we just switch to using it\n> without \"CC_IS_GCC && (GCC_VERSION >= 110100)\" guard.\n> \n> Is it worth to maintain 2 version of the function? I don't know...\n\nGCC 11 was released five years and a day ago. The last GCC 11 release\n(that of 11.5) is not even two years ago though (but there will be no\nmore!)\n\nSo it would be not conservative at all to require GCC 11 as minimum now,\nsome people might even call it a bit aggressive. But in a year (or\nmaybe two) the lay of the land will be rather different.\n\n\nSegher","headers":{"Return-Path":"\n ","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=H4WjIMjs;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org;\n envelope-from=linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from bombadil.infradead.org (bombadil.infradead.org\n [IPv6:2607:7c80:54:3::133])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g4dKZ3HNSz1yHv\n\tfor ; Tue, 28 Apr 2026 21:21:06 +1000 (AEST)","from localhost ([::1] helo=bombadil.infradead.org)\n\tby bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux))\n\tid 1wHgUz-00000001L3i-0xry;\n\tTue, 28 Apr 2026 11:21:05 +0000","from gate.crashing.org ([63.228.1.57])\n\tby bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux))\n\tid 1wHgUw-00000001L32-2Vcd;\n\tTue, 28 Apr 2026 11:21:04 +0000","from gate.crashing.org (localhost [127.0.0.1])\n\tby gate.crashing.org (8.18.1/8.18.1/Debian-2) with ESMTP id 63SBKIxF1057213;\n\tTue, 28 Apr 2026 06:20:18 -0500","(from segher@localhost)\n\tby gate.crashing.org (8.18.1/8.18.1/Submit) id 63SBKHXo1057211;\n\tTue, 28 Apr 2026 06:20:17 -0500"],"DKIM-Signature":"v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;\n\td=lists.infradead.org; s=bombadil.20210309; h=Sender:\n\tContent-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post:\n\tList-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:\n\tMessage-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:\n\tResent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:\n\tList-Owner; bh=2IzGQGSMYqWdMcyYY5AF+gwI1QLU3X838si2CAwh/LA=; b=H4WjIMjs+iEOFU\n\tI61vrAiPdfWkQh7bd2L/ri39Kp7RccxNRKIsxdM/IBYWQT7h3hEDF1MJLDARMm8R1fqlVn5xxVVIc\n\t8X9qU/oF4AB96fY1TAPjyWxVdg1qkuATsTkncMUz6O/UMsvQ2oKcF7egY1pRTg5le5j70iIg40vWt\n\t/f3gWmm6Qa17/IofQlFTokfv+8FIjccjUY6H00ilF+Eyn9jw07Mtz941nkvjmI2QtXk3nUNIVjKAZ\n\tFuG8LfJDwyXhfP1MnfpytdSQHQXLB0H784bYaoSw3qo/WYauMgiXEo8LxgA2bXZrRJY3l0G1fRuJL\n\t0hbjAzNNtc7h78o6Gx1A==;","X-Authentication-Warning":"gate.crashing.org: segher set sender to\n segher@kernel.crashing.org using -f","Date":"Tue, 28 Apr 2026 06:20:17 -0500","From":"Segher Boessenkool ","To":"Yury Norov ","Cc":"Linus Torvalds ,\n \"Christophe Leroy (CS GROUP)\" ,\n Andrew Morton ,\n David Laight ,\n Thomas Gleixner , linux-alpha@vger.kernel.org,\n Yury Norov , linux-kernel@vger.kernel.org,\n linux-snps-arc@lists.infradead.org,\n linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,\n linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,\n linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,\n sparclinux@vger.kernel.org, linux-um@lists.infradead.org,\n dmaengine@vger.kernel.org, linux-efi@vger.kernel.org,\n linux-fsi@lists.ozlabs.org, amd-gfx@lists.freedesktop.org,\n dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,\n linux-wpan@vger.kernel.org, netdev@vger.kernel.org,\n linux-wireless@vger.kernel.org, linux-spi@vger.kernel.org,\n linux-media@vger.kernel.org, linux-staging@lists.linux.dev,\n linux-serial@vger.kernel.org, linux-usb@vger.kernel.org,\n xen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org,\n ocfs2-devel@lists.linux.dev, bpf@vger.kernel.org,\n kasan-dev@googlegroups.com, linux-mm@kvack.org,\n linux-x25@vger.kernel.org, rust-for-linux@vger.kernel.org,\n linux-sound@vger.kernel.org, sound-open-firmware@alsa-project.org,\n linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org,\n loongarch@lists.linux.dev, linux-m68k@vger.kernel.org,\n linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org,\n linux-sh@vger.kernel.org, linux-arch@vger.kernel.org","Subject":"Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()","Message-ID":"","References":"\n <0ee46bb228d97163fbdc14f2a7c52b93d8bc34ce.1777306795.git.chleroy@kernel.org>\n \n <63a4d0f6-0eb3-48cd-9f98-bf7b223b2606@kernel.org>\n \n \n ","MIME-Version":"1.0","Content-Disposition":"inline","In-Reply-To":"","X-CRM114-Version":"20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 ","X-CRM114-CacheID":"sfid-20260428_042102_834754_31566CF4 ","X-CRM114-Status":"GOOD ( 21.19 )","X-Spam-Score":"-1.9 (-)","X-Spam-Report":"Spam detection software,\n running on the system \"bombadil.infradead.org\",\n has NOT identified this incoming email as spam. The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: Hi! On Mon, Apr 27, 2026 at 06:30:16PM -0400,\n Yury Norov wrote:\n > On Mon, Apr 27, 2026 at 02:52:05PM -0700, Linus Torvalds wrote: > > On\n Mon, 27 Apr 2026 at 12:19, Yury Norov wrote: > [...]\n Content analysis details: (-1.9 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 SPF_PASS SPF: sender matches SPF record\n -0.0 SPF_HELO_PASS SPF: HELO matches SPF record\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]","X-BeenThere":"linux-snps-arc@lists.infradead.org","X-Mailman-Version":"2.1.34","Precedence":"list","List-Id":"Linux on Synopsys ARC Processors ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Sender":"\"linux-snps-arc\" ","Errors-To":"\n linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org"}}]