KVM: x86: mask unsupported XSAVE entries from leaf 0Dh index 0

XSAVE entries that KVM does not support are reported by
KVM_GET_SUPPORTED_CPUID for leaf 0Dh index 0 if the host supports them;
they should be left out unless there is also hypervisor support for them.

Sub-leafs are correctly handled in supported_xcr0_bit, fix index 0
to match.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

2 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b110fe6c03d4..a03a9faf81b0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -182,7 +182,7 @@ static bool supported_xcr0_bit(unsigned bit)
 {
         u64 mask = ((u64)1 << bit);
 
-        return mask & (XSTATE_FP | XSTATE_SSE | XSTATE_YMM) & host_xcr0;
+        return mask & KVM_SUPPORTED_XCR0 & host_xcr0;
 }
 
 #define F(x) bit(X86_FEATURE_##x)
@@ -383,6 +383,8 @@ static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
         case 0xd: {
                 int idx, i;
 
+                entry->eax &= host_xcr0 & KVM_SUPPORTED_XCR0;
+                entry->edx &= (host_xcr0 & KVM_SUPPORTED_XCR0) >> 32;
                 entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                 for (idx = 1, i = 1; idx < 64; ++idx) {
                         if (*nent >= maxnent)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index e224f7a671b6..587fb9ede436 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -122,6 +122,7 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
         gva_t addr, void *val, unsigned int bytes,
         struct x86_exception *exception);
 
+#define KVM_SUPPORTED_XCR0      (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
 extern u64 host_xcr0;
 
 extern struct static_key kvm_no_apic_vcpu;