[{"id":1776503,"web_url":"http://patchwork.ozlabs.org/comment/1776503/","msgid":"","list_archive_url":null,"date":"2017-09-27T17:51:11","subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","submitter":{"id":72104,"url":"http://patchwork.ozlabs.org/api/people/72104/","name":"Richard Henderson","email":"richard.henderson@linaro.org"},"content":"On 09/27/2017 10:00 AM, David Hildenbrand wrote:\n> + case PSW_ASC_HOME:\n> + return !(env->cregs[13] & _ASCE_PRIVATE_SPACE);\n> + default:\n> + /* We don't support access register mode */\n> + error_report(\"unsupported addressing mode\");\n> + exit(1);\n\nI think g_assert_not_reached() is sufficient for cases like this.\n\nOh, it's just code movement. Nevermind, perhaps.\nModulo the outcome of discussion on patch 1,\n\nReviewed-by: Richard Henderson \n\n\nr~","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; helo=lists.gnu.org;\n\tenvelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n\treceiver=)","ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=linaro.org header.i=@linaro.org\n\theader.b=\"byYA+4kf\"; dkim-atps=neutral"],"Received":["from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11])\n\t(using TLSv1 with cipher AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3y2QPG17ZVz9tXd\n\tfor ;\n\tThu, 28 Sep 2017 03:51:45 +1000 (AEST)","from localhost ([::1]:55794 helo=lists.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.71) (envelope-from\n\t)\n\tid 1dxGUm-0004Yu-4M\n\tfor incoming@patchwork.ozlabs.org; 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Linux x86_64; rv:52.0) Gecko/20100101\n\tThunderbird/52.3.0","MIME-Version":"1.0","In-Reply-To":"<20170927170027.8539-3-david@redhat.com>","Content-Type":"text/plain; charset=utf-8","Content-Language":"en-US","Content-Transfer-Encoding":"7bit","X-detected-operating-system":"by eggs.gnu.org: Genre and OS details not\n\trecognized.","X-Received-From":"2607:f8b0:400e:c00::22c","Subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Christian Borntraeger , thuth@redhat.com,\n\tcohuck@redhat.com, Alexander Graf ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"}},{"id":1776761,"web_url":"http://patchwork.ozlabs.org/comment/1776761/","msgid":"<466fa6a0-ac91-66aa-aabb-a15a8ac62e0f@redhat.com>","list_archive_url":null,"date":"2017-09-28T04:50:39","subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","submitter":{"id":66152,"url":"http://patchwork.ozlabs.org/api/people/66152/","name":"Thomas Huth","email":"thuth@redhat.com"},"content":"On 27.09.2017 19:00, David Hildenbrand wrote:\n> This is a neat way to implement low address protection, whereby\n> only the first 512 bytes of the first two pages (each 4096 bytes) of\n> every address space are protected.\n> \n> Store a tec of 0 for the access exception, this is what is defined by\n> Enhanced Suppression on Protection in case of a low address protection\n> (Bit 61 set to 0, rest undefined).\n> \n> We have to make sure to to pass the access address, not the masked page\n> address into mmu_translate*().\n> \n> Drop the check from testblock. So we can properly test this via\n> kvm-unit-tests.\n> \n> This will check every access going through one of the MMUs.\n> \n> Signed-off-by: David Hildenbrand \n> ---\n> target/s390x/excp_helper.c | 3 +-\n> target/s390x/mem_helper.c | 8 ----\n> target/s390x/mmu_helper.c | 96 +++++++++++++++++++++++++++++-----------------\n> 3 files changed, 62 insertions(+), 45 deletions(-)\n[...]\n> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c\n> index 9daa0fd8e2..44a15449d2 100644\n> --- a/target/s390x/mmu_helper.c\n> +++ b/target/s390x/mmu_helper.c\n> @@ -106,6 +106,37 @@ static void trigger_page_fault(CPUS390XState *env, target_ulong vaddr,\n> trigger_access_exception(env, type, ilen, tec);\n> }\n> \n> +/* check whether the address would be proteted by Low-Address Protection */\n> +static bool is_low_address(uint64_t addr)\n> +{\n> + return addr < 512 || (addr >= 4096 && addr < 4607);\n> +}\n\nI like the check from the kernel sources better:\n\nstatic inline int is_low_address(unsigned long ga)\n{\n /* Check for address ranges 0..511 and 4096..4607 */\n return (ga & ~0x11fful) == 0;\n}\n\n... that might result in slightly faster code (depending on the\ncompiler, of course).\n\n Thomas","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; helo=lists.gnu.org;\n\tenvelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n\treceiver=)","ext-mx08.extmail.prod.ext.phx2.redhat.com;\n\tdmarc=none (p=none dis=none) header.from=redhat.com","ext-mx08.extmail.prod.ext.phx2.redhat.com;\n\tspf=fail smtp.mailfrom=thuth@redhat.com"],"Received":["from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11])\n\t(using TLSv1 with cipher AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3y2j2M3Byzz9sNc\n\tfor ;\n\tThu, 28 Sep 2017 14:51:18 +1000 (AEST)","from localhost ([::1]:57375 helo=lists.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.71) (envelope-from\n\t)\n\tid 1dxQn1-0001Uu-TW\n\tfor incoming@patchwork.ozlabs.org; Thu, 28 Sep 2017 00:51:11 -0400","from eggs.gnu.org ([2001:4830:134:3::10]:59366)\n\tby lists.gnu.org with esmtp (Exim 4.71)\n\t(envelope-from ) id 1dxQmg-0001Uo-Ag\n\tfor qemu-devel@nongnu.org; Thu, 28 Sep 2017 00:50:51 -0400","from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)\n\t(envelope-from ) id 1dxQmc-0003Fa-DZ\n\tfor qemu-devel@nongnu.org; Thu, 28 Sep 2017 00:50:50 -0400","from mx1.redhat.com ([209.132.183.28]:49464)\n\tby eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)\n\t(Exim 4.71) (envelope-from ) id 1dxQmc-0003FQ-7K\n\tfor qemu-devel@nongnu.org; Thu, 28 Sep 2017 00:50:46 -0400","from smtp.corp.redhat.com\n\t(int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15])\n\t(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby mx1.redhat.com (Postfix) with ESMTPS id C8F07C04E529;\n\tThu, 28 Sep 2017 04:50:44 +0000 (UTC)","from [10.36.116.86] (ovpn-116-86.ams2.redhat.com [10.36.116.86])\n\tby smtp.corp.redhat.com (Postfix) with ESMTPS id C43B463BCE;\n\tThu, 28 Sep 2017 04:50:40 +0000 (UTC)"],"DMARC-Filter":"OpenDMARC Filter v1.3.2 mx1.redhat.com C8F07C04E529","To":"David Hildenbrand , qemu-devel@nongnu.org","References":"<20170927170027.8539-1-david@redhat.com>\n\t<20170927170027.8539-3-david@redhat.com>","From":"Thomas Huth ","Message-ID":"<466fa6a0-ac91-66aa-aabb-a15a8ac62e0f@redhat.com>","Date":"Thu, 28 Sep 2017 06:50:39 +0200","User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101\n\tThunderbird/52.3.0","MIME-Version":"1.0","In-Reply-To":"<20170927170027.8539-3-david@redhat.com>","Content-Type":"text/plain; charset=utf-8","Content-Language":"en-US","Content-Transfer-Encoding":"7bit","X-Scanned-By":"MIMEDefang 2.79 on 10.5.11.15","X-Greylist":"Sender IP whitelisted, not delayed by milter-greylist-4.5.16\n\t(mx1.redhat.com [10.5.110.32]);\n\tThu, 28 Sep 2017 04:50:45 +0000 (UTC)","X-detected-operating-system":"by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic]\n\t[fuzzy]","X-Received-From":"209.132.183.28","Subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Christian Borntraeger , cohuck@redhat.com,\n\tRichard Henderson ,\n\tAlexander Graf ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"}},{"id":1777020,"web_url":"http://patchwork.ozlabs.org/comment/1777020/","msgid":"<3d5ea6d8-b3bf-b1a5-b4a1-082ff49ae842@redhat.com>","list_archive_url":null,"date":"2017-09-28T13:08:11","subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","submitter":{"id":70402,"url":"http://patchwork.ozlabs.org/api/people/70402/","name":"David Hildenbrand","email":"david@redhat.com"},"content":"On 28.09.2017 06:50, Thomas Huth wrote:\n> On 27.09.2017 19:00, David Hildenbrand wrote:\n>> This is a neat way to implement low address protection, whereby\n>> only the first 512 bytes of the first two pages (each 4096 bytes) of\n>> every address space are protected.\n>>\n>> Store a tec of 0 for the access exception, this is what is defined by\n>> Enhanced Suppression on Protection in case of a low address protection\n>> (Bit 61 set to 0, rest undefined).\n>>\n>> We have to make sure to to pass the access address, not the masked page\n>> address into mmu_translate*().\n>>\n>> Drop the check from testblock. So we can properly test this via\n>> kvm-unit-tests.\n>>\n>> This will check every access going through one of the MMUs.\n>>\n>> Signed-off-by: David Hildenbrand \n>> ---\n>> target/s390x/excp_helper.c | 3 +-\n>> target/s390x/mem_helper.c | 8 ----\n>> target/s390x/mmu_helper.c | 96 +++++++++++++++++++++++++++++-----------------\n>> 3 files changed, 62 insertions(+), 45 deletions(-)\n> [...]\n>> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c\n>> index 9daa0fd8e2..44a15449d2 100644\n>> --- a/target/s390x/mmu_helper.c\n>> +++ b/target/s390x/mmu_helper.c\n>> @@ -106,6 +106,37 @@ static void trigger_page_fault(CPUS390XState *env, target_ulong vaddr,\n>> trigger_access_exception(env, type, ilen, tec);\n>> }\n>> \n>> +/* check whether the address would be proteted by Low-Address Protection */\n>> +static bool is_low_address(uint64_t addr)\n>> +{\n>> + return addr < 512 || (addr >= 4096 && addr < 4607);\n>> +}\n> \n> I like the check from the kernel sources better:\n> \n> static inline int is_low_address(unsigned long ga)\n> {\n> /* Check for address ranges 0..511 and 4096..4607 */\n> return (ga & ~0x11fful) == 0;\n> }\n> \n> ... that might result in slightly faster code (depending on the\n> compiler, of course).\n\nI think that lim (readability) -> 0. Without that comment you're at\nfirst sight really clueless what this is about.\n\nMy check exactly corresponds to the wording in the PoP (and smart\ncompilers should be able to optimize).\n\nBut I don't have a strong opinion on this micro optimization.\n\nThanks\n\n> \n> Thomas\n>","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; helo=lists.gnu.org;\n\tenvelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n\treceiver=)","ext-mx07.extmail.prod.ext.phx2.redhat.com;\n\tdmarc=none (p=none dis=none) header.from=redhat.com","ext-mx07.extmail.prod.ext.phx2.redhat.com;\n\tspf=fail smtp.mailfrom=david@redhat.com"],"Received":["from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11])\n\t(using TLSv1 with cipher AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3y2w4R5Pknz9t5Y\n\tfor ;\n\tThu, 28 Sep 2017 23:08:55 +1000 (AEST)","from localhost ([::1]:59204 helo=lists.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.71) (envelope-from\n\t)\n\tid 1dxYYf-00059T-St\n\tfor incoming@patchwork.ozlabs.org; Thu, 28 Sep 2017 09:08:53 -0400","from eggs.gnu.org ([2001:4830:134:3::10]:59839)\n\tby lists.gnu.org with esmtp (Exim 4.71)\n\t(envelope-from ) id 1dxYYB-00052P-Fi\n\tfor qemu-devel@nongnu.org; Thu, 28 Sep 2017 09:08:33 -0400","from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)\n\t(envelope-from ) id 1dxYY3-0000pk-TA\n\tfor qemu-devel@nongnu.org; Thu, 28 Sep 2017 09:08:20 -0400","from mx1.redhat.com ([209.132.183.28]:54600)\n\tby eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)\n\t(Exim 4.71) (envelope-from ) id 1dxYY3-0000pL-Ij\n\tfor qemu-devel@nongnu.org; Thu, 28 Sep 2017 09:08:15 -0400","from smtp.corp.redhat.com\n\t(int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15])\n\t(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby mx1.redhat.com (Postfix) with ESMTPS id A21ABC1217C8;\n\tThu, 28 Sep 2017 13:08:14 +0000 (UTC)","from [10.36.117.191] (ovpn-117-191.ams2.redhat.com [10.36.117.191])\n\tby smtp.corp.redhat.com (Postfix) with ESMTP id D76A57E68B;\n\tThu, 28 Sep 2017 13:08:12 +0000 (UTC)"],"DMARC-Filter":"OpenDMARC Filter v1.3.2 mx1.redhat.com A21ABC1217C8","To":"Thomas Huth , qemu-devel@nongnu.org","References":"<20170927170027.8539-1-david@redhat.com>\n\t<20170927170027.8539-3-david@redhat.com>\n\t<466fa6a0-ac91-66aa-aabb-a15a8ac62e0f@redhat.com>","From":"David Hildenbrand ","Organization":"Red Hat GmbH","Message-ID":"<3d5ea6d8-b3bf-b1a5-b4a1-082ff49ae842@redhat.com>","Date":"Thu, 28 Sep 2017 15:08:11 +0200","User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101\n\tThunderbird/52.3.0","MIME-Version":"1.0","In-Reply-To":"<466fa6a0-ac91-66aa-aabb-a15a8ac62e0f@redhat.com>","Content-Type":"text/plain; charset=utf-8","Content-Language":"en-US","Content-Transfer-Encoding":"7bit","X-Scanned-By":"MIMEDefang 2.79 on 10.5.11.15","X-Greylist":"Sender IP whitelisted, not delayed by milter-greylist-4.5.16\n\t(mx1.redhat.com [10.5.110.31]);\n\tThu, 28 Sep 2017 13:08:14 +0000 (UTC)","X-detected-operating-system":"by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic]\n\t[fuzzy]","X-Received-From":"209.132.183.28","Subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Christian Borntraeger , cohuck@redhat.com,\n\tRichard Henderson ,\n\tAlexander Graf ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"}},{"id":1785217,"web_url":"http://patchwork.ozlabs.org/comment/1785217/","msgid":"<469b7729-0e9a-1c20-6a68-b3b8e55bafb4@redhat.com>","list_archive_url":null,"date":"2017-10-12T08:41:33","subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","submitter":{"id":66152,"url":"http://patchwork.ozlabs.org/api/people/66152/","name":"Thomas Huth","email":"thuth@redhat.com"},"content":"On 29.09.2017 13:27, Cornelia Huck wrote:\n> On Thu, 28 Sep 2017 15:08:11 +0200\n> David Hildenbrand wrote:\n> \n>> On 28.09.2017 06:50, Thomas Huth wrote:\n>>> On 27.09.2017 19:00, David Hildenbrand wrote: \n>>>> This is a neat way to implement low address protection, whereby\n>>>> only the first 512 bytes of the first two pages (each 4096 bytes) of\n>>>> every address space are protected.\n>>>>\n>>>> Store a tec of 0 for the access exception, this is what is defined by\n>>>> Enhanced Suppression on Protection in case of a low address protection\n>>>> (Bit 61 set to 0, rest undefined).\n>>>>\n>>>> We have to make sure to to pass the access address, not the masked page\n>>>> address into mmu_translate*().\n>>>>\n>>>> Drop the check from testblock. So we can properly test this via\n>>>> kvm-unit-tests.\n>>>>\n>>>> This will check every access going through one of the MMUs.\n>>>>\n>>>> Signed-off-by: David Hildenbrand \n>>>> ---\n>>>> target/s390x/excp_helper.c | 3 +-\n>>>> target/s390x/mem_helper.c | 8 ----\n>>>> target/s390x/mmu_helper.c | 96 +++++++++++++++++++++++++++++-----------------\n>>>> 3 files changed, 62 insertions(+), 45 deletions(-) \n>>> [...] \n>>>> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c\n>>>> index 9daa0fd8e2..44a15449d2 100644\n>>>> --- a/target/s390x/mmu_helper.c\n>>>> +++ b/target/s390x/mmu_helper.c\n>>>> @@ -106,6 +106,37 @@ static void trigger_page_fault(CPUS390XState *env, target_ulong vaddr,\n>>>> trigger_access_exception(env, type, ilen, tec);\n>>>> }\n>>>> \n>>>> +/* check whether the address would be proteted by Low-Address Protection */\n>>>> +static bool is_low_address(uint64_t addr)\n>>>> +{\n>>>> + return addr < 512 || (addr >= 4096 && addr < 4607);\n>>>> +} \n>>>\n>>> I like the check from the kernel sources better:\n>>>\n>>> static inline int is_low_address(unsigned long ga)\n>>> {\n>>> /* Check for address ranges 0..511 and 4096..4607 */\n>>> return (ga & ~0x11fful) == 0;\n>>> }\n>>>\n>>> ... that might result in slightly faster code (depending on the\n>>> compiler, of course). \n>>\n>> I think that lim (readability) -> 0. Without that comment you're at\n>> first sight really clueless what this is about.\n>>\n>> My check exactly corresponds to the wording in the PoP (and smart\n>> compilers should be able to optimize).\n>>\n>> But I don't have a strong opinion on this micro optimization.\n> \n> FWIW, I'd be happy with both, but has anyone actually looked at the\n> generated code?\n\nThis is what I get for David's original code:\n\n 80000510: c4 18 00 00 0d a4 lgrl %r1,80002058 \n 80000516: a7 29 01 ff lghi %r2,511\n 8000051a: ec 12 00 4f c0 65 clgrjnh %r1,%r2,800005b8 \n 80000520: a7 1b f0 00 aghi %r1,-4096\n 80000524: c2 1e 00 00 01 fe clgfi %r1,510\n 8000052a: a7 18 00 00 lhi %r1,0\n 8000052e: b9 99 00 11 slbr %r1,%r1\n 80000532: 13 11 lcr %r1,%r1\n 80000534: c4 1f 00 00 0d 96 strl %r1,80002060 \n\nAnd this is the optimized kernel version:\n\n 8000054a: c4 18 00 00 0d 7f lgrl %r1,80002048 \n 80000550: a5 17 ee 00 nill %r1,60928\n 80000554: b9 00 00 11 lpgr %r1,%r1\n 80000558: a7 1b ff ff aghi %r1,-1\n 8000055c: eb 11 00 3f 00 0c srlg %r1,%r1,63\n 80000562: c4 1f 00 00 0d 77 strl %r1,80002050 \n\nSo that's indeed a little bit better :-)\n(I was using GCC 4.8.5 from RHEL7, with -O2)\n\nBy the way, I think there's a bug in David's code: It should either be\n\"addr <= 4607\" or \"addr < 4608\" instead of \"addr < 4607\".\n\nWith that bug fixed, David's version get's optimized even more:\n\n 80000510: c4 18 00 00 0d a4 lgrl %r1,80002058 \n 80000516: a5 17 ef ff nill %r1,61439\n 8000051a: c2 1e 00 00 01 ff clgfi %r1,511\n 80000520: a7 18 00 00 lhi %r1,0\n 80000524: b9 99 00 11 slbr %r1,%r1\n 80000528: 13 11 lcr %r1,%r1\n 8000052a: c4 1f 00 00 0d 9b strl %r1,80002060 \n\n... so the difference is really very minimal in that case --> We could\nreally use the more readable version, I think.\n\n Thomas","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; helo=lists.gnu.org;\n\tenvelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n\treceiver=)","ext-mx01.extmail.prod.ext.phx2.redhat.com;\n\tdmarc=none (p=none dis=none) header.from=redhat.com","ext-mx01.extmail.prod.ext.phx2.redhat.com;\n\tspf=fail smtp.mailfrom=thuth@redhat.com"],"Received":["from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11])\n\t(using TLSv1 with cipher AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3yCPVJ0gHyz9t2d\n\tfor ;\n\tThu, 12 Oct 2017 19:42:14 +1100 (AEDT)","from localhost ([::1]:44320 helo=lists.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.71) (envelope-from\n\t)\n\tid 1e2Z4E-0001re-0w\n\tfor incoming@patchwork.ozlabs.org; Thu, 12 Oct 2017 04:42:10 -0400","from eggs.gnu.org ([2001:4830:134:3::10]:34443)\n\tby lists.gnu.org with esmtp (Exim 4.71)\n\t(envelope-from ) id 1e2Z3r-0001r9-4p\n\tfor qemu-devel@nongnu.org; Thu, 12 Oct 2017 04:41:51 -0400","from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)\n\t(envelope-from ) id 1e2Z3n-00035g-P2\n\tfor qemu-devel@nongnu.org; Thu, 12 Oct 2017 04:41:47 -0400","from mx1.redhat.com ([209.132.183.28]:36860)\n\tby eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)\n\t(Exim 4.71) (envelope-from )\n\tid 1e2Z3n-00035D-Gf; Thu, 12 Oct 2017 04:41:43 -0400","from smtp.corp.redhat.com\n\t(int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12])\n\t(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby mx1.redhat.com (Postfix) with ESMTPS id 446547F3F2;\n\tThu, 12 Oct 2017 08:41:42 +0000 (UTC)","from [10.33.192.189] (dhcp-192-189.str.redhat.com [10.33.192.189])\n\tby smtp.corp.redhat.com (Postfix) with ESMTPS id 0F8CB6957D;\n\tThu, 12 Oct 2017 08:41:34 +0000 (UTC)"],"DMARC-Filter":"OpenDMARC Filter v1.3.2 mx1.redhat.com 446547F3F2","To":"Cornelia Huck , David Hildenbrand ","References":"<20170927170027.8539-1-david@redhat.com>\n\t<20170927170027.8539-3-david@redhat.com>\n\t<466fa6a0-ac91-66aa-aabb-a15a8ac62e0f@redhat.com>\n\t<3d5ea6d8-b3bf-b1a5-b4a1-082ff49ae842@redhat.com>\n\t<20170929132717.23ecf350.cohuck@redhat.com>","From":"Thomas Huth ","Message-ID":"<469b7729-0e9a-1c20-6a68-b3b8e55bafb4@redhat.com>","Date":"Thu, 12 Oct 2017 10:41:33 +0200","User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101\n\tThunderbird/52.3.0","MIME-Version":"1.0","In-Reply-To":"<20170929132717.23ecf350.cohuck@redhat.com>","Content-Type":"text/plain; charset=utf-8","Content-Language":"en-US","X-Scanned-By":"MIMEDefang 2.79 on 10.5.11.12","X-Greylist":"Sender IP whitelisted, not delayed by milter-greylist-4.5.16\n\t(mx1.redhat.com [10.5.110.25]);\n\tThu, 12 Oct 2017 08:41:42 +0000 (UTC)","Content-Transfer-Encoding":"quoted-printable","X-detected-operating-system":"by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic]\n\t[fuzzy]","X-Received-From":"209.132.183.28","Subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Christian Borntraeger , qemu-s390x@nongnu.org,\n\tRichard Henderson ,\n\tqemu-devel@nongnu.org, Alexander Graf ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"}},{"id":1787187,"web_url":"http://patchwork.ozlabs.org/comment/1787187/","msgid":"","list_archive_url":null,"date":"2017-10-16T07:20:54","subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","submitter":{"id":70402,"url":"http://patchwork.ozlabs.org/api/people/70402/","name":"David Hildenbrand","email":"david@redhat.com"},"content":"On 12.10.2017 10:41, Thomas Huth wrote:\n> On 29.09.2017 13:27, Cornelia Huck wrote:\n>> On Thu, 28 Sep 2017 15:08:11 +0200\n>> David Hildenbrand wrote:\n>>\n>>> On 28.09.2017 06:50, Thomas Huth wrote:\n>>>> On 27.09.2017 19:00, David Hildenbrand wrote: \n>>>>> This is a neat way to implement low address protection, whereby\n>>>>> only the first 512 bytes of the first two pages (each 4096 bytes) of\n>>>>> every address space are protected.\n>>>>>\n>>>>> Store a tec of 0 for the access exception, this is what is defined by\n>>>>> Enhanced Suppression on Protection in case of a low address protection\n>>>>> (Bit 61 set to 0, rest undefined).\n>>>>>\n>>>>> We have to make sure to to pass the access address, not the masked page\n>>>>> address into mmu_translate*().\n>>>>>\n>>>>> Drop the check from testblock. So we can properly test this via\n>>>>> kvm-unit-tests.\n>>>>>\n>>>>> This will check every access going through one of the MMUs.\n>>>>>\n>>>>> Signed-off-by: David Hildenbrand \n>>>>> ---\n>>>>> target/s390x/excp_helper.c | 3 +-\n>>>>> target/s390x/mem_helper.c | 8 ----\n>>>>> target/s390x/mmu_helper.c | 96 +++++++++++++++++++++++++++++-----------------\n>>>>> 3 files changed, 62 insertions(+), 45 deletions(-) \n>>>> [...] \n>>>>> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c\n>>>>> index 9daa0fd8e2..44a15449d2 100644\n>>>>> --- a/target/s390x/mmu_helper.c\n>>>>> +++ b/target/s390x/mmu_helper.c\n>>>>> @@ -106,6 +106,37 @@ static void trigger_page_fault(CPUS390XState *env, target_ulong vaddr,\n>>>>> trigger_access_exception(env, type, ilen, tec);\n>>>>> }\n>>>>> \n>>>>> +/* check whether the address would be proteted by Low-Address Protection */\n>>>>> +static bool is_low_address(uint64_t addr)\n>>>>> +{\n>>>>> + return addr < 512 || (addr >= 4096 && addr < 4607);\n>>>>> +} \n>>>>\n>>>> I like the check from the kernel sources better:\n>>>>\n>>>> static inline int is_low_address(unsigned long ga)\n>>>> {\n>>>> /* Check for address ranges 0..511 and 4096..4607 */\n>>>> return (ga & ~0x11fful) == 0;\n>>>> }\n>>>>\n>>>> ... that might result in slightly faster code (depending on the\n>>>> compiler, of course). \n>>>\n>>> I think that lim (readability) -> 0. Without that comment you're at\n>>> first sight really clueless what this is about.\n>>>\n>>> My check exactly corresponds to the wording in the PoP (and smart\n>>> compilers should be able to optimize).\n>>>\n>>> But I don't have a strong opinion on this micro optimization.\n>>\n>> FWIW, I'd be happy with both, but has anyone actually looked at the\n>> generated code?\n> \n> This is what I get for David's original code:\n> \n> 80000510: c4 18 00 00 0d a4 lgrl %r1,80002058 \n> 80000516: a7 29 01 ff lghi %r2,511\n> 8000051a: ec 12 00 4f c0 65 clgrjnh %r1,%r2,800005b8 \n> 80000520: a7 1b f0 00 aghi %r1,-4096\n> 80000524: c2 1e 00 00 01 fe clgfi %r1,510\n> 8000052a: a7 18 00 00 lhi %r1,0\n> 8000052e: b9 99 00 11 slbr %r1,%r1\n> 80000532: 13 11 lcr %r1,%r1\n> 80000534: c4 1f 00 00 0d 96 strl %r1,80002060 \n> \n> And this is the optimized kernel version:\n> \n> 8000054a: c4 18 00 00 0d 7f lgrl %r1,80002048 \n> 80000550: a5 17 ee 00 nill %r1,60928\n> 80000554: b9 00 00 11 lpgr %r1,%r1\n> 80000558: a7 1b ff ff aghi %r1,-1\n> 8000055c: eb 11 00 3f 00 0c srlg %r1,%r1,63\n> 80000562: c4 1f 00 00 0d 77 strl %r1,80002050 \n> \n> So that's indeed a little bit better :-)\n> (I was using GCC 4.8.5 from RHEL7, with -O2)\n> \n> By the way, I think there's a bug in David's code: It should either be\n> \"addr <= 4607\" or \"addr < 4608\" instead of \"addr < 4607\".\n> \n> With that bug fixed, David's version get's optimized even more:\n> \n> 80000510: c4 18 00 00 0d a4 lgrl %r1,80002058 \n> 80000516: a5 17 ef ff nill %r1,61439\n> 8000051a: c2 1e 00 00 01 ff clgfi %r1,511\n> 80000520: a7 18 00 00 lhi %r1,0\n> 80000524: b9 99 00 11 slbr %r1,%r1\n> 80000528: 13 11 lcr %r1,%r1\n> 8000052a: c4 1f 00 00 0d 9b strl %r1,80002060 \n> \n> ... so the difference is really very minimal in that case --> We could\n> really use the more readable version, I think.\n> \n> Thomas\n> \n\nVery right, I'll fix that.\n\nNice way to find BUGs - comparing generated code :)\n\nThanks!","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; 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Linux x86_64; rv:52.0) Gecko/20100101\n\tThunderbird/52.3.0","MIME-Version":"1.0","In-Reply-To":"<469b7729-0e9a-1c20-6a68-b3b8e55bafb4@redhat.com>","Content-Type":"text/plain; charset=utf-8","Content-Language":"en-US","Content-Transfer-Encoding":"7bit","X-Scanned-By":"MIMEDefang 2.79 on 10.5.11.12","X-Greylist":"Sender IP whitelisted, not delayed by milter-greylist-4.5.16\n\t(mx1.redhat.com [10.5.110.25]);\n\tMon, 16 Oct 2017 07:20:57 +0000 (UTC)","X-detected-operating-system":"by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic]\n\t[fuzzy]","X-Received-From":"209.132.183.28","Subject":"Re: [Qemu-devel] [PATCH RFC 2/3] s390x/tcg: low-address protection\n\tsupport","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.21","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"Christian Borntraeger , qemu-s390x@nongnu.org,\n\tRichard Henderson ,\n\tqemu-devel@nongnu.org, Alexander Graf ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"\"Qemu-devel\"\n\t"}}]