KVM: x86: do not save guest-unsupported XSAVE state

commit 00c87e9a70a17b355b81c36adedf05e84f54e10d upstream.

Saving unsupported state prevents migration when the new host does not
support a XSAVE feature of the original host, even if the feature is not
exposed to the guest.

We've masked host features with guest-visible features before, with
4344ee981e21 ("KVM: x86: only copy XSAVE state for the supported
features") and dropped it when implementing XSAVES.  Do it again.

Fixes: df1daba7d1cb ("KVM: x86: support XSAVES usage in the host")
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 25a6efcfdf7fd3da0f0350f2f97e0a033658e9f6..e75095fa414ef5d48d15eb8fce32cac55ea5fc0c 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3057,6 +3057,7 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
        memcpy(dest, xsave, XSAVE_HDR_OFFSET);
 
        /* Set XSTATE_BV */
+       xstate_bv &= vcpu->arch.guest_supported_xcr0 | XFEATURE_MASK_FPSSE;
        *(u64 *)(dest + XSAVE_HDR_OFFSET) = xstate_bv;
 
        /*