KVM: cpuid: recompute CPUID 0xD.0:EBX,ECX

We reused host EBX and ECX, but KVM might not support all features;
emulated XSAVE size should be smaller.

EBX depends on unknown XCR0, so we default to ECX.

SDM CPUID (EAX = 0DH, ECX = 0):
 EBX Bits 31-00: Maximum size (bytes, from the beginning of the
     XSAVE/XRSTOR save area) required by enabled features in XCR0. May
     be different than ECX if some features at the end of the XSAVE save
     area are not enabled.

 ECX Bit 31-00: Maximum size (bytes, from the beginning of the
     XSAVE/XRSTOR save area) of the XSAVE/XRSTOR save area required by
     all supported features in the processor, i.e all the valid bit
     fields in XCR0.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Tested-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 644bfe828ce1a58606dca5334cdae3e26032bbf0..8a80737ee6e6ec14bc7d9a6ffe08d9f580d3c890 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -464,6 +464,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                u64 supported = kvm_supported_xcr0();
 
                entry->eax &= supported;
+               entry->ebx = xstate_required_size(supported, false);
+               entry->ecx = entry->ebx;
                entry->edx &= supported >> 32;
                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                if (!supported)