Full equality check of CPUID data on update (kvm_cpuid_check_equal()) may
fail for SGX enabled CPUs as CPUID.(EAX=0x12,ECX=1) is currently being
mangled in kvm_vcpu_after_set_cpuid(). Move it to
__kvm_update_cpuid_runtime() and split off cpuid_get_supported_xcr0()
helper as 'vcpu->arch.guest_supported_xcr0' update needs (logically)
to stay in kvm_vcpu_after_set_cpuid().
Cc: stable@xxxxxxxxxxxxxxx
Fixes: feb627e8d6f6 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN")
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/kvm/cpuid.c | 54 +++++++++++++++++++++++++++-----------------
1 file changed, 33 insertions(+), 21 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 3902c28fb6cb..89d7822a8f5b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -196,10 +196,26 @@ void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
vcpu->arch.pv_cpuid.features = best->eax;
}
+/*
+ * Calculate guest's supported XCR0 taking into account guest CPUID data and
+ * supported_xcr0 (comprised of host configuration and KVM_SUPPORTED_XCR0).
+ */
+static u64 cpuid_get_supported_xcr0(struct kvm_cpuid_entry2 *entries, int nent)
+{
+ struct kvm_cpuid_entry2 *best;
+
+ best = cpuid_entry2_find(entries, nent, 0xd, 0);
+ if (!best)
+ return 0;
+
+ return (best->eax | ((u64)best->edx << 32)) & supported_xcr0;
+}
+
static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entries,
int nent)
{
struct kvm_cpuid_entry2 *best;
+ u64 guest_supported_xcr0 = cpuid_get_supported_xcr0(entries, nent);
best = cpuid_entry2_find(entries, nent, 1, 0);
if (best) {
@@ -238,6 +254,21 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
vcpu->arch.ia32_misc_enable_msr &
MSR_IA32_MISC_ENABLE_MWAIT);
}
+
+ /*
+ * Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate
+ * the supported XSAVE Feature Request Mask (XFRM), i.e. the enclave's
+ * requested XCR0 value. The enclave's XFRM must be a subset of XCRO
+ * at the time of EENTER, thus adjust the allowed XFRM by the guest's
+ * supported XCR0. Similar to XCR0 handling, FP and SSE are forced to
+ * '1' even on CPUs that don't support XSAVE.
+ */
+ best = cpuid_entry2_find(entries, nent, 0x12, 0x1);
+ if (best) {
+ best->ecx &= guest_supported_xcr0 & 0xffffffff;
+ best->edx &= guest_supported_xcr0 >> 32;
+ best->ecx |= XFEATURE_MASK_FPSSE;
+ }
}
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
@@ -261,27 +292,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
kvm_apic_set_version(vcpu);
}
- best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
- if (!best)
- vcpu->arch.guest_supported_xcr0 = 0;
- else
- vcpu->arch.guest_supported_xcr0 =
- (best->eax | ((u64)best->edx << 32)) & supported_xcr0;
-
- /*
- * Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate
- * the supported XSAVE Feature Request Mask (XFRM), i.e. the enclave's
- * requested XCR0 value. The enclave's XFRM must be a subset of XCRO
- * at the time of EENTER, thus adjust the allowed XFRM by the guest's
- * supported XCR0. Similar to XCR0 handling, FP and SSE are forced to
- * '1' even on CPUs that don't support XSAVE.
- */
- best = kvm_find_cpuid_entry(vcpu, 0x12, 0x1);
- if (best) {
- best->ecx &= vcpu->arch.guest_supported_xcr0 & 0xffffffff;
- best->edx &= vcpu->arch.guest_supported_xcr0 >> 32;
- best->ecx |= XFEATURE_MASK_FPSSE;
- }
+ vcpu->arch.guest_supported_xcr0 =
+ cpuid_get_supported_xcr0(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
kvm_update_pv_runtime(vcpu);
--
2.34.1
