[PATCH] KVM: x86: Fix re-execution of patched vmmcall

[PATCH] KVM: x86: Fix re-execution of patched vmmcall

[Jan Kiszka]

For a very long time (since 2b3d2a20), the path handling a vmmcall
instruction of the guest on an Intel host only applied the patch but no
longer handled the hypercall. The reverse case, vmcall on AMD hosts, is
fine. As both em_vmcall and em_vmmcall actually have to do the same, we
can fix the issue by consolidating both into the same handler.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 arch/x86/kvm/emulate.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 106c015..c941abe 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3323,7 +3323,7 @@ static int em_clts(struct x86_emulate_ctxt *ctxt)
 	return X86EMUL_CONTINUE;
 }
 
-static int em_vmcall(struct x86_emulate_ctxt *ctxt)
+static int em_hypercall(struct x86_emulate_ctxt *ctxt)
 {
 	int rc = ctxt->ops->fix_hypercall(ctxt);
 
@@ -3395,17 +3395,6 @@ static int em_lgdt(struct x86_emulate_ctxt *ctxt)
 	return em_lgdt_lidt(ctxt, true);
 }
 
-static int em_vmmcall(struct x86_emulate_ctxt *ctxt)
-{
-	int rc;
-
-	rc = ctxt->ops->fix_hypercall(ctxt);
-
-	/* Disable writeback. */
-	ctxt->dst.type = OP_NONE;
-	return rc;
-}
-
 static int em_lidt(struct x86_emulate_ctxt *ctxt)
 {
 	return em_lgdt_lidt(ctxt, false);
@@ -3769,7 +3758,7 @@ static int check_perm_out(struct x86_emulate_ctxt *ctxt)
 
 static const struct opcode group7_rm0[] = {
 	N,
-	I(SrcNone | Priv | EmulateOnUD,	em_vmcall),
+	I(SrcNone | Priv | EmulateOnUD,	em_hypercall),
 	N, N, N, N, N, N,
 };
 
@@ -3781,7 +3770,7 @@ static const struct opcode group7_rm1[] = {
 
 static const struct opcode group7_rm3[] = {
 	DIP(SrcNone | Prot | Priv,		vmrun,		check_svme_pa),
-	II(SrcNone  | Prot | EmulateOnUD,	em_vmmcall,	vmmcall),
+	II(SrcNone  | Prot | EmulateOnUD,	em_hypercall,	vmmcall),
 	DIP(SrcNone | Prot | Priv,		vmload,		check_svme_pa),
 	DIP(SrcNone | Prot | Priv,		vmsave,		check_svme_pa),
 	DIP(SrcNone | Prot | Priv,		stgi,		check_svme),
-- 
2.1.4

Re: [PATCH] KVM: x86: Fix re-execution of patched vmmcall

[Marcelo Tosatti]

On Mon, Mar 09, 2015 at 08:27:43PM +0100, Jan Kiszka wrote:
> For a very long time (since 2b3d2a20), the path handling a vmmcall
> instruction of the guest on an Intel host only applied the patch but no
> longer handled the hypercall. The reverse case, vmcall on AMD hosts, is
> fine. As both em_vmcall and em_vmmcall actually have to do the same, we
> can fix the issue by consolidating both into the same handler.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

Applied, thanks.