2019-08-15 16:41:53

by Sean Christopherson

Subject: [PATCH] KVM: x86: Fix x86_decode_insn() return when fetching insn bytes fails

Jump to the common error handling in x86_decode_insn() if
__do_insn_fetch_bytes() fails so that its error code is converted to the
appropriate return type. Although the various helpers used by
x86_decode_insn() return X86EMUL_* values, x86_decode_insn() itself
returns EMULATION_FAILED or EMULATION_OK.

This doesn't cause a functional issue as the sole caller,
x86_emulate_instruction(), currently only cares about success vs.
failure, and success is indicated by '0' for both types
(X86EMUL_CONTINUE and EMULATION_OK).

Fixes: 285ca9e948fa ("KVM: emulate: speed up do_insn_fetch")
Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/emulate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8e409ad448f9..6d2273e71020 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5126,7 +5126,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
else {
rc = __do_insn_fetch_bytes(ctxt, 1);
if (rc != X86EMUL_CONTINUE)
- return rc;
+ goto done;
}

switch (mode) {
--
2.22.0

2019-08-16 21:17:41

by Jim Mattson

Subject: Re: [PATCH] KVM: x86: Fix x86_decode_insn() return when fetching insn bytes fails

On Thu, Aug 15, 2019 at 9:20 AM Sean Christopherson
<[email protected]> wrote:
>
> Jump to the common error handling in x86_decode_insn() if
> __do_insn_fetch_bytes() fails so that its error code is converted to the
> appropriate return type. Although the various helpers used by
> x86_decode_insn() return X86EMUL_* values, x86_decode_insn() itself
> returns EMULATION_FAILED or EMULATION_OK.
>
> This doesn't cause a functional issue as the sole caller,
> x86_emulate_instruction(), currently only cares about success vs.
> failure, and success is indicated by '0' for both types
> (X86EMUL_CONTINUE and EMULATION_OK).
>
> Fixes: 285ca9e948fa ("KVM: emulate: speed up do_insn_fetch")
> Signed-off-by: Sean Christopherson <[email protected]>
Reviewed-by: Jim Mattson <[email protected]>

2019-08-19 15:19:42

by Paolo Bonzini

Subject: Re: [PATCH] KVM: x86: Fix x86_decode_insn() return when fetching insn bytes fails

On 15/08/19 18:20, Sean Christopherson wrote:
> Jump to the common error handling in x86_decode_insn() if
> __do_insn_fetch_bytes() fails so that its error code is converted to the
> appropriate return type. Although the various helpers used by
> x86_decode_insn() return X86EMUL_* values, x86_decode_insn() itself
> returns EMULATION_FAILED or EMULATION_OK.
>
> This doesn't cause a functional issue as the sole caller,
> x86_emulate_instruction(), currently only cares about success vs.
> failure, and success is indicated by '0' for both types
> (X86EMUL_CONTINUE and EMULATION_OK).
>
> Fixes: 285ca9e948fa ("KVM: emulate: speed up do_insn_fetch")
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/emulate.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 8e409ad448f9..6d2273e71020 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -5126,7 +5126,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
> else {
> rc = __do_insn_fetch_bytes(ctxt, 1);
> if (rc != X86EMUL_CONTINUE)
> - return rc;
> + goto done;
> }
>
> switch (mode) {
>

Queued, thanks.

Paolo