From nobody Mon Oct 6 08:08:20 2025 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A1C94247DE1; Wed, 23 Jul 2025 17:54:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753293285; cv=none; b=kSvgWU+hSbgaFC46pB12w4+UqsnrzUiykUnEAIQHXcZdVGdZm8stkyo+oZtSox4lg61CKch6vrA3qoDSr+9LjFvVc+PlbsFg+UGuXF76twvFZlj/gJI/jFlNkQFB+zLzIlmEAjBgcRMU/lGsSpf/25IpRg4UY6Cg7xZZ6W4jS2M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753293285; c=relaxed/simple; bh=cAkS9B7sQ6Q4fMNM8C2U2UQnUsMw1QYVDgTlHwoKFkk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LlqWKUMg8RvIjp9M4pJXBGrBBL9dDpUAoJdRjetth8pEzfVXrN/m1FryxT1q1tVI4McdV+JPmUuHtkznev7hZQ4wvmqlLPX+vBqQ2dCN4K1HVxLp8uHY/UZKxYReAt+ZvzSHGn4V8yzcGfrHXZHou+DHzasWXAwZ4VbC1vmROSI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=IDVf7jQs; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="IDVf7jQs" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 56NHrf001284522 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 23 Jul 2025 10:53:54 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 56NHrf001284522 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025072201; t=1753293235; bh=vAH6XFDgf2g1Xi+hKsymZubWXlznbyb6kDUSvmyxflg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IDVf7jQsRw8+nvq9T8f+ZkBjar7HTW4xRVCkc19n3Uin75xq+3DPoBt5TPBLR96+B nqb8OlnalZkDVPL711DfX8b9WWlhbIWfRaa6Vbg5Ac/VKJWGU9QuAiGCa0qlUibJeq pz9X5LHTsN8DP2aFpZd0r7gpiF0PgeCg9iAHxkeG4l6VSkxSvdWyI85eJsE5+aFgEh KxOejQY91wLbo9dn8Ut3XrNImfwXAwOUGk3BJC2U+lKsBqM8PkJlk7AuRfOPbQe/aL Tp3XnYUAza1bn5o6r+u85BcznmRtndU+503E+YiYj67kwB6yYsnFZ1kySiuGZz5Dk+ x6I0QmZ27Hu+Q== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org Cc: pbonzini@redhat.com, seanjc@google.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, xin@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, chao.gao@intel.com, hch@infradead.org Subject: [PATCH v5 10/23] KVM: VMX: Add support for FRED context save/restore Date: Wed, 23 Jul 2025 10:53:28 -0700 Message-ID: <20250723175341.1284463-11-xin@zytor.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250723175341.1284463-1-xin@zytor.com> References: <20250723175341.1284463-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Xin Li Handle FRED MSR access requests, allowing FRED context to be set/get from both host and guest. During VM save/restore and live migration, FRED context needs to be saved/restored, which requires FRED MSRs to be accessed from userspace, e.g., Qemu. Note, handling of MSR_IA32_FRED_SSP0, i.e., MSR_IA32_PL0_SSP, is not added yet, which is done in the KVM CET patch set. Signed-off-by: Xin Li Signed-off-by: Xin Li (Intel) Tested-by: Shan Kang Tested-by: Xuelian Guo --- Change in v5: * Use the newly added guest MSR read/write helpers (Sean). * Check the size of fred_msr_vmcs_fields[] using static_assert() (Sean). * Rewrite setting FRED MSRs to make it much easier to read (Sean). * Add TB from Xuelian Guo. Changes since v2: * Add a helper to convert FRED MSR index to VMCS field encoding to make the code more compact (Chao Gao). * Get rid of the "host_initiated" check because userspace has to set CPUID before MSRs (Chao Gao & Sean Christopherson). * Address a few cleanup comments (Sean Christopherson). Changes since v1: * Use kvm_cpu_cap_has() instead of cpu_feature_enabled() (Chao Gao). * Fail host requested FRED MSRs access if KVM cannot virtualize FRED (Chao Gao). * Handle the case FRED MSRs are valid but KVM cannot virtualize FRED (Chao Gao). * Add sanity checks when writing to FRED MSRs. --- arch/x86/kvm/vmx/vmx.c | 45 ++++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/x86.c | 42 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 87 insertions(+) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 53dce136e24b..fd995787b6cf 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1388,6 +1388,18 @@ static void vmx_write_guest_kernel_gs_base(struct vc= pu_vmx *vmx, u64 data) vmx_write_guest_host_msr(vmx, MSR_KERNEL_GS_BASE, data, &vmx->msr_guest_kernel_gs_base); } + +static u64 vmx_read_guest_fred_rsp0(struct vcpu_vmx *vmx) +{ + return vmx_read_guest_host_msr(vmx, MSR_IA32_FRED_RSP0, + &vmx->msr_guest_fred_rsp0); +} + +static void vmx_write_guest_fred_rsp0(struct vcpu_vmx *vmx, u64 data) +{ + vmx_write_guest_host_msr(vmx, MSR_IA32_FRED_RSP0, data, + &vmx->msr_guest_fred_rsp0); +} #endif =20 static void grow_ple_window(struct kvm_vcpu *vcpu) @@ -1989,6 +2001,27 @@ int vmx_get_feature_msr(u32 msr, u64 *data) } } =20 +#ifdef CONFIG_X86_64 +static const u32 fred_msr_vmcs_fields[] =3D { + GUEST_IA32_FRED_RSP1, + GUEST_IA32_FRED_RSP2, + GUEST_IA32_FRED_RSP3, + GUEST_IA32_FRED_STKLVLS, + GUEST_IA32_FRED_SSP1, + GUEST_IA32_FRED_SSP2, + GUEST_IA32_FRED_SSP3, + GUEST_IA32_FRED_CONFIG, +}; + +static_assert(MSR_IA32_FRED_CONFIG - MSR_IA32_FRED_RSP1 =3D=3D + ARRAY_SIZE(fred_msr_vmcs_fields) - 1); + +static u32 fred_msr_to_vmcs(u32 msr) +{ + return fred_msr_vmcs_fields[msr - MSR_IA32_FRED_RSP1]; +} +#endif + /* * Reads an msr value (of 'msr_info->index') into 'msr_info->data'. * Returns 0 on success, non-0 otherwise. @@ -2011,6 +2044,12 @@ int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_da= ta *msr_info) case MSR_KERNEL_GS_BASE: msr_info->data =3D vmx_read_guest_kernel_gs_base(vmx); break; + case MSR_IA32_FRED_RSP0: + msr_info->data =3D vmx_read_guest_fred_rsp0(vmx); + break; + case MSR_IA32_FRED_RSP1 ... MSR_IA32_FRED_CONFIG: + msr_info->data =3D vmcs_read64(fred_msr_to_vmcs(msr_info->index)); + break; #endif case MSR_EFER: return kvm_get_msr_common(vcpu, msr_info); @@ -2234,6 +2273,12 @@ int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_da= ta *msr_info) vmx_update_exception_bitmap(vcpu); } break; + case MSR_IA32_FRED_RSP0: + vmx_write_guest_fred_rsp0(vmx, data); + break; + case MSR_IA32_FRED_RSP1 ... MSR_IA32_FRED_CONFIG: + vmcs_write64(fred_msr_to_vmcs(msr_index), data); + break; #endif case MSR_IA32_SYSENTER_CS: if (is_guest_mode(vcpu)) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a1c49bc681c4..ae23a3470ecd 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -323,6 +323,9 @@ static const u32 msrs_to_save_base[] =3D { MSR_STAR, #ifdef CONFIG_X86_64 MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR, + MSR_IA32_FRED_RSP0, MSR_IA32_FRED_RSP1, MSR_IA32_FRED_RSP2, + MSR_IA32_FRED_RSP3, MSR_IA32_FRED_STKLVLS, MSR_IA32_FRED_SSP1, + MSR_IA32_FRED_SSP2, MSR_IA32_FRED_SSP3, MSR_IA32_FRED_CONFIG, #endif MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA, MSR_IA32_FEAT_CTL, MSR_IA32_BNDCFGS, MSR_TSC_AUX, @@ -1870,6 +1873,37 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 = index, u64 data, =20 data =3D (u32)data; break; + case MSR_IA32_FRED_STKLVLS: + if (!guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) + return 1; + break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_RSP3: + case MSR_IA32_FRED_SSP1 ... MSR_IA32_FRED_CONFIG: + u64 reserved_bits =3D 0; + + if (!guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) + return 1; + + if (is_noncanonical_msr_address(data, vcpu)) + return 1; + + switch (index) { + case MSR_IA32_FRED_CONFIG: + reserved_bits =3D BIT_ULL(11) | GENMASK_ULL(5, 4) | BIT_ULL(2); + break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_RSP3: + reserved_bits =3D GENMASK_ULL(5, 0); + break; + case MSR_IA32_FRED_SSP1 ... MSR_IA32_FRED_SSP3: + reserved_bits =3D GENMASK_ULL(2, 0); + break; + default: + WARN_ON_ONCE(1); + return 1; + } + if (data & reserved_bits) + return 1; + break; } =20 msr.data =3D data; @@ -1914,6 +1948,10 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, = u64 *data, !guest_cpu_cap_has(vcpu, X86_FEATURE_RDPID)) return 1; break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG: + if (!guest_cpu_cap_has(vcpu, X86_FEATURE_FRED)) + return 1; + break; } =20 msr.index =3D index; @@ -7365,6 +7403,10 @@ static void kvm_probe_msr_to_save(u32 msr_index) if (!(kvm_get_arch_capabilities() & ARCH_CAP_TSX_CTRL_MSR)) return; break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG: + if (!kvm_cpu_cap_has(X86_FEATURE_FRED)) + return; + break; default: break; } --=20 2.50.1