[{"id":3682576,"web_url":"http://patchwork.ozlabs.org/comment/3682576/","msgid":"","list_archive_url":null,"date":"2026-04-27T09:18:05","subject":"Re: [PATCH v10 5/7] target/arm/cpu64: Define cpreg migration\n tolerance for KVM_REG_ARM_VENDOR_HYP_BMAP_2","submitter":{"id":5111,"url":"http://patchwork.ozlabs.org/api/people/5111/","name":"Peter Maydell","email":"peter.maydell@linaro.org"},"content":"On Mon, 20 Apr 2026 at 15:06, Eric Auger wrote:\n>\n> KVM_REG_ARM_VENDOR_HYP_BMAP_2 pseudo FW register is exposed\n> from v6.15 onwards. Backward migration from a >= v6.15 to an older\n> kernel would fail without cpreg migration tolerance definition\n> for this register. If the register is present on source but not\n> on destination, its value must be checked to make sure it matches\n> the reset value, ie. 0, meaning no service is exposed to the guest,\n> hence the choice of a ToleranceOnlySrcTestValue migration\n> tolerance.\n>\n> Signed-off-by: Eric Auger \n>\n> ---\n>\n> v9 -> v10\n> - Use ToleranceOnlySrcTestValue\n> ---\n> target/arm/cpu64.c | 11 +++++++++++\n> 1 file changed, 11 insertions(+)\n>\n> diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c\n> index e7014022df4..a93ad2da5ad 100644\n> --- a/target/arm/cpu64.c\n> +++ b/target/arm/cpu64.c\n> @@ -834,6 +834,17 @@ static void kvm_arm_set_cpreg_mig_tolerances(ARMCPU *cpu)\n> 0, 0, ToleranceNotOnBothEnds);\n> arm_register_cpreg_mig_tolerance(cpu, ARM64_SYS_REG(3, 0, 10, 2, 3),\n> 0, 0, ToleranceNotOnBothEnds);\n> +\n> + /*\n> + * KVM_REG_ARM_VENDOR_HYP_BMAP_2 pseudo FW register is exposed\n> + * from v6.15 onwards. Backward migration from a >= v6.15 to an older\n> + * kernel would fail without cpreg migration tolerance definition.\n> + * If the register is present on source but not on destination, make\n> + * sure it has its reset value, ie. 0, meaning no service is exposed\n> + * to the guest.\n> + */\n> + arm_register_cpreg_mig_tolerance(cpu, KVM_REG_ARM_FW_FEAT_BMAP_REG(3),\n> + UINT64_MAX, 0, ToleranceOnlySrcTestValue);\n> }\n> #endif\n\nReviewed-by: Peter Maydell \n\nthanks\n-- PMM","headers":{"Return-Path":"","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 unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=jU7FH2cL;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists1p.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g3yfl0NPZz1yJX\n\tfor ; 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Mon, 27 Apr 2026\n 02:18:16 -0700 (PDT)","MIME-Version":"1.0","References":"<20260420140552.104369-1-eric.auger@redhat.com>\n <20260420140552.104369-6-eric.auger@redhat.com>","In-Reply-To":"<20260420140552.104369-6-eric.auger@redhat.com>","From":"Peter Maydell ","Date":"Mon, 27 Apr 2026 10:18:05 +0100","X-Gm-Features":"AVHnY4Jk2G_QaUXXF-ToRhKsty7cByPhEM1z72OjTIi4V98G6qYyhT2FKUf-ujc","Message-ID":"\n ","Subject":"Re: [PATCH v10 5/7] target/arm/cpu64: Define cpreg migration\n tolerance for KVM_REG_ARM_VENDOR_HYP_BMAP_2","To":"Eric Auger ","Cc":"eric.auger.pro@gmail.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org,\n cohuck@redhat.com, sebott@redhat.com, peterx@redhat.com, philmd@linaro.org,\n alex.bennee@linaro.org","Content-Type":"text/plain; charset=\"UTF-8\"","Received-SPF":"pass client-ip=2607:f8b0:4864:20::b133;\n envelope-from=peter.maydell@linaro.org; helo=mail-yx1-xb133.google.com","X-Spam_score_int":"-20","X-Spam_score":"-2.1","X-Spam_bar":"--","X-Spam_report":"(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=ham autolearn_force=no","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"}}]