diff options
| author | Yang Weijiang <weijiang.yang@intel.com> | 2025-09-19 15:32:14 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-09-23 09:00:46 -0700 |
| commit | 9622e116d0d25f1ddc47bf0328612cc7d87d20f2 (patch) | |
| tree | d04b49bfa68057b41f0c08e3e99a235d0ddd81cc | |
| parent | 338543cbe033e56dcc8c13adcdf6c228953c0829 (diff) | |
KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS
Update CPUID.(EAX=0DH,ECX=1).EBX to reflect current required xstate size
due to XSS MSR modification.
CPUID(EAX=0DH,ECX=1).EBX reports the required storage size of all enabled
xstate features in (XCR0 | IA32_XSS). The CPUID value can be used by guest
before allocate sufficient xsave buffer.
Note, KVM does not yet support any XSS based features, i.e. supported_xss
is guaranteed to be zero at this time.
Opportunistically skip CPUID updates if XSS value doesn't change.
Suggested-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Mathias Krause <minipli@grsecurity.net>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/cpuid.c | 3 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 2 |
2 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 6b8b5d8b13cc..32fde9e80c28 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -316,7 +316,8 @@ static void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) best = kvm_find_cpuid_entry_index(vcpu, 0xD, 1); if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) || cpuid_entry_has(best, X86_FEATURE_XSAVEC))) - best->ebx = xstate_required_size(vcpu->arch.xcr0, true); + best->ebx = xstate_required_size(vcpu->arch.xcr0 | + vcpu->arch.ia32_xss, true); } static bool kvm_cpuid_has_hyperv(struct kvm_vcpu *vcpu) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6ae12e8c9d05..d142cbc71aaa 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3993,6 +3993,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) */ if (data & ~vcpu->arch.guest_supported_xss) return 1; + if (vcpu->arch.ia32_xss == data) + break; vcpu->arch.ia32_xss = data; vcpu->arch.cpuid_dynamic_bits_dirty = true; break; |