From nobody Fri Nov 14 22:07:40 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1760502688063220.0048133930219; Tue, 14 Oct 2025 21:31:28 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v8t5i-0000MV-LO; Wed, 15 Oct 2025 00:26:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v8t5g-0000K1-En; Wed, 15 Oct 2025 00:26:20 -0400 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v8t5b-0002pp-QX; Wed, 15 Oct 2025 00:26:20 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 7C10115D9CF; Wed, 15 Oct 2025 07:24:59 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 1FAF829FE78; Wed, 15 Oct 2025 07:25:21 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Paolo Bonzini , Hector Cao , Michael Tokarev Subject: [Stable-10.1.2 10/11] target/i386: add compatibility property for arch_capabilities Date: Wed, 15 Oct 2025 07:25:14 +0300 Message-ID: <20251015042520.68556-10-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1760502693258158500 Content-Type: text/plain; charset="utf-8" From: Paolo Bonzini Prior to v10.1, if requested by user, arch-capabilities is always on despite the fact that CPUID advertises it to be off/unvailable. This causes a migration issue for VMs that are run on a machine without arch-capabilities and expect this feature to be present on the destination host with QEMU 10.1. Add a compatibility property to restore the legacy behavior for all machines with version prior to 10.1. To preserve the functionality (added by 10.1) of turning off ARCH_CAPABILITIES where Windows does not like it, use directly the guest CPU vendor: x86_cpu_get_supported_feature_word is not KVM-specific and therefore should not necessarily use the host CPUID. Co-authored-by: Hector Cao Signed-off-by: Hector Cao Fixes: d3a24134e37 ("target/i386: do not expose ARCH_CAPABILITIES on AMD CP= U", 2025-07-17) Signed-off-by: Paolo Bonzini (cherry picked from commit e9efa4a77168ac2816bf9471f878252ce6224710) Signed-off-by: Michael Tokarev diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 2f58e73d33..2504365bc2 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -84,6 +84,7 @@ GlobalProperty pc_compat_10_0[] =3D { { TYPE_X86_CPU, "x-consistent-cache", "false" }, { TYPE_X86_CPU, "x-vendor-cpuid-only-v2", "false" }, + { TYPE_X86_CPU, "x-arch-cap-always-on", "true" }, }; const size_t pc_compat_10_0_len =3D G_N_ELEMENTS(pc_compat_10_0); =20 diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 6d85149e6e..fe369bb128 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -7539,6 +7539,20 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *= cpu, FeatureWord w) #endif break; =20 + case FEAT_7_0_EDX: + /* + * Windows does not like ARCH_CAPABILITIES on AMD machines at all. + * Do not show the fake ARCH_CAPABILITIES MSR that KVM sets up, + * except if needed for migration. + * + * When arch_cap_always_on is removed, this tweak can move to + * kvm_arch_get_supported_cpuid. + */ + if (cpu && IS_AMD_CPU(&cpu->env) && !cpu->arch_cap_always_on) { + unavail =3D CPUID_7_0_EDX_ARCH_CAPABILITIES; + } + break; + default: break; } @@ -10004,6 +10018,9 @@ static const Property x86_cpu_properties[] =3D { true), DEFINE_PROP_BOOL("x-l1-cache-per-thread", X86CPU, l1_cache_per_core, t= rue), DEFINE_PROP_BOOL("x-force-cpuid-0x1f", X86CPU, force_cpuid_0x1f, false= ), + + DEFINE_PROP_BOOL("x-arch-cap-always-on", X86CPU, + arch_cap_always_on, false), }; =20 #ifndef CONFIG_USER_ONLY diff --git a/target/i386/cpu.h b/target/i386/cpu.h index e0be7a7406..414ca968e8 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -2314,6 +2314,12 @@ struct ArchCPU { /* Forcefully disable KVM PV features not exposed in guest CPUIDs */ bool kvm_pv_enforce_cpuid; =20 + /* + * Expose arch-capabilities unconditionally even on AMD models, for ba= ckwards + * compatibility with QEMU <10.1. + */ + bool arch_cap_always_on; + /* Number of physical address bits supported */ uint32_t phys_bits; =20 diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 5621200be0..96035c27cd 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -503,12 +503,8 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uin= t32_t function, * Linux v4.17-v4.20 incorrectly return ARCH_CAPABILITIES on SVM h= osts. * We can detect the bug by checking if MSR_IA32_ARCH_CAPABILITIES= is * returned by KVM_GET_MSR_INDEX_LIST. - * - * But also, because Windows does not like ARCH_CAPABILITIES on AMD - * mcahines at all, do not show the fake ARCH_CAPABILITIES MSR that - * KVM sets up. */ - if (!has_msr_arch_capabs || !(edx & CPUID_7_0_EDX_ARCH_CAPABILITIE= S)) { + if (!has_msr_arch_capabs) { ret &=3D ~CPUID_7_0_EDX_ARCH_CAPABILITIES; } } else if (function =3D=3D 7 && index =3D=3D 1 && reg =3D=3D R_EAX) { --=20 2.47.3