[PATCH v2 12/23] x86/fpu: Prepare xfd_err in struct fpu_guest

[Jing Liu]

When XFD causes an instruction to generate #NM, IA32_XFD_ERR
contains information about which disabled state components are
being accessed. The #NM handler is expected to check this
information and then enable the state components by clearing
IA32_XFD for the faulting task (if having permission).

If the XFD_ERR value generated in guest is consumed/clobbered
by the host before the guest itself doing so. This may lead to
non-XFD-related #NM treated as XFD #NM in host (due to non-zero
value in XFD_ERR), or XFD-related #NM treated as non-XFD #NM in
guest (XFD_ERR cleared by the host #NM handler).

Introduce a new field in fpu_guest to save the guest xfd_err value.
KVM is expected to save guest xfd_err before preemption is enabled
and restore it right before entering the guest (with preemption
disabled).

Signed-off-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Signed-off-by: Jing Liu <jing2.liu@xxxxxxxxx>
---
 arch/x86/include/asm/fpu/types.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index c752d0aa23a4..3795d0573773 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -517,6 +517,11 @@ struct fpu_guest {
 	 */
 	u64				perm;
 
+	/*
+	 * @xfd_err:			Save the guest value.
+	 */
+	u64				xfd_err;
+
 	/*
 	 * @fpstate:			Pointer to the allocated guest fpstate
 	 */
-- 
2.27.0