[PATCH v2 1/2] x86/sev/vc: fix efi runtime instruction emulation

[Gerd Hoffmann <kraxel@redhat.com>]

In case efi_mm is active go use the userspace instruction decoder which
supports fetching instructions from active_mm.  This is needed to make
instruction emulation work for EFI runtime code, so it can use cpuid
and rdmsr.

EFI runtime code uses the cpuid instruction to gather information about
the environment it is running in, such as SEV being enabled or not, and
choose (if needed) the SEV code path for ioport access.

EFI runtime code uses the rdmsr instruction to get the location of the
CAA page (see SVSM spec, section 4.2 - "Post Boot").

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 arch/x86/coco/sev/vc-handle.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/coco/sev/vc-handle.c b/arch/x86/coco/sev/vc-handle.c
index 0989d98da130..01c78182da88 100644
--- a/arch/x86/coco/sev/vc-handle.c
+++ b/arch/x86/coco/sev/vc-handle.c
@@ -17,6 +17,7 @@
 #include <linux/mm.h>
 #include <linux/io.h>
 #include <linux/psp-sev.h>
+#include <linux/efi.h>
 #include <uapi/linux/sev-guest.h>
 
 #include <asm/init.h>
@@ -180,7 +181,7 @@ static enum es_result __vc_decode_kern_insn(struct es_em_ctxt *ctxt)
 
 static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
 {
-	if (user_mode(ctxt->regs))
+	if (user_mode(ctxt->regs) || current->active_mm == &efi_mm)
 		return __vc_decode_user_insn(ctxt);
 	else
 		return __vc_decode_kern_insn(ctxt);
-- 
2.49.0