diff options
| author | Yang Weijiang <weijiang.yang@intel.com> | 2025-09-19 15:32:15 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-09-23 09:00:46 -0700 |
| commit | 779ed05511f2931b89fcd0087aba2fcca8890715 (patch) | |
| tree | d248127abe1f00f5a24a361cfd4b55d1d72689a2 | |
| parent | 9622e116d0d25f1ddc47bf0328612cc7d87d20f2 (diff) | |
KVM: x86: Initialize kvm_caps.supported_xss
Set original kvm_caps.supported_xss to (host_xss & KVM_SUPPORTED_XSS) if
XSAVES is supported. host_xss contains the host supported xstate feature
bits for thread FPU context switch, KVM_SUPPORTED_XSS includes all KVM
enabled XSS feature bits, the resulting value represents the supervisor
xstates that are available to guest and are backed by host FPU framework
for swapping {guest,host} XSAVE-managed registers/MSRs.
[sean: relocate and enhance comment about PT / XSS[8] ]
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Chao Gao <chao.gao@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>
Reviewed-by: Xiaoyao Li <xiaoyao.li@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/20250919223258.1604852-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/x86.c | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d142cbc71aaa..831c5e488de3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -217,6 +217,14 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs; | XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \ | XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE) +/* + * Note, KVM supports exposing PT to the guest, but does not support context + * switching PT via XSTATE (KVM's PT virtualization relies on perf; swapping + * PT via guest XSTATE would clobber perf state), i.e. KVM doesn't support + * IA32_XSS[bit 8] (guests can/must use RDMSR/WRMSR to save/restore PT MSRs). + */ +#define KVM_SUPPORTED_XSS 0 + bool __read_mostly allow_smaller_maxphyaddr = 0; EXPORT_SYMBOL_GPL(allow_smaller_maxphyaddr); @@ -3986,11 +3994,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_IA32_XSS: if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVES)) return KVM_MSR_RET_UNSUPPORTED; - /* - * KVM supports exposing PT to the guest, but does not support - * IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than - * XSAVES/XRSTORS to save/restore PT MSRs. - */ + if (data & ~vcpu->arch.guest_supported_xss) return 1; if (vcpu->arch.ia32_xss == data) @@ -9822,14 +9826,17 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) kvm_host.xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK); kvm_caps.supported_xcr0 = kvm_host.xcr0 & KVM_SUPPORTED_XCR0; } + + if (boot_cpu_has(X86_FEATURE_XSAVES)) { + rdmsrq(MSR_IA32_XSS, kvm_host.xss); + kvm_caps.supported_xss = kvm_host.xss & KVM_SUPPORTED_XSS; + } + kvm_caps.supported_quirks = KVM_X86_VALID_QUIRKS; kvm_caps.inapplicable_quirks = KVM_X86_CONDITIONAL_QUIRKS; rdmsrq_safe(MSR_EFER, &kvm_host.efer); - if (boot_cpu_has(X86_FEATURE_XSAVES)) - rdmsrq(MSR_IA32_XSS, kvm_host.xss); - kvm_init_pmu_capability(ops->pmu_ops); if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES)) |