On 8/21/2025 9:30 PM, Chao Gao wrote:
From: Yang Weijiang <weijiang.yang@xxxxxxxxx>
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.
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>
Tested-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Tested-by: John Allen <john.allen@xxxxxxx>
Tested-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
arch/x86/kvm/x86.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 75b7a29721bb..6b01c6e9330e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -220,6 +220,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
+#define KVM_SUPPORTED_XSS 0
+
bool __read_mostly allow_smaller_maxphyaddr = 0;
EXPORT_SYMBOL_GPL(allow_smaller_maxphyaddr);
@@ -9793,14 +9795,17 @@ 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;
+ }
Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Btw, since we now have KVM_SUPPORTED_XSS to cap the supported bits, it
seems we can remove the
kvm_caps.supported_xss = 0;
in both vmx_set_cpu_caps() and svm_set_cpu_caps().
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))
