2023-12-12 10:00:49

by Julian Stecklina

Subject: [PATCH] KVM: x86/emulator: emulate movbe with operand-size prefix

From: Thomas Prescher <[email protected]>

The MOVBE instruction can come with an operand-size prefix (66h). In
this, case the x86 emulation code returns EMULATION_FAILED.

It turns out that em_movbe can already handle this case and all that
is missing is an entry in respective opcode tables to populate
gprefix->pfx_66.

Signed-off-by: Thomas Prescher <[email protected]>
Signed-off-by: Julian Stecklina <[email protected]>
---
arch/x86/kvm/emulate.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 2673cd5c46cb..08013e158b2d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4502,11 +4502,11 @@ static const struct instr_dual instr_dual_0f_38_f1 = {
};

static const struct gprefix three_byte_0f_38_f0 = {
- ID(0, &instr_dual_0f_38_f0), N, N, N
+ ID(0, &instr_dual_0f_38_f0), ID(0, &instr_dual_0f_38_f0), N, N
};

static const struct gprefix three_byte_0f_38_f1 = {
- ID(0, &instr_dual_0f_38_f1), N, N, N
+ ID(0, &instr_dual_0f_38_f1), ID(0, &instr_dual_0f_38_f1), N, N
};

/*
--
2.42.0

2023-12-17 12:12:23

by Borislav Petkov

Subject: Re: [PATCH] KVM: x86/emulator: emulate movbe with operand-size prefix

On Tue, Dec 12, 2023 at 10:59:37AM +0100, Julian Stecklina wrote:
> From: Thomas Prescher <[email protected]>
>
> The MOVBE instruction can come with an operand-size prefix (66h). In
> this, case the x86 emulation code returns EMULATION_FAILED.
>
> It turns out that em_movbe can already handle this case and all that
> is missing is an entry in respective opcode tables to populate
> gprefix->pfx_66.
>
> Signed-off-by: Thomas Prescher <[email protected]>
> Signed-off-by: Julian Stecklina <[email protected]>
> ---
> arch/x86/kvm/emulate.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 2673cd5c46cb..08013e158b2d 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -4502,11 +4502,11 @@ static const struct instr_dual instr_dual_0f_38_f1 = {
> };
>
> static const struct gprefix three_byte_0f_38_f0 = {
> - ID(0, &instr_dual_0f_38_f0), N, N, N
> + ID(0, &instr_dual_0f_38_f0), ID(0, &instr_dual_0f_38_f0), N, N
> };
>
> static const struct gprefix three_byte_0f_38_f1 = {
> - ID(0, &instr_dual_0f_38_f1), N, N, N
> + ID(0, &instr_dual_0f_38_f1), ID(0, &instr_dual_0f_38_f1), N, N
> };
>
> /*
> --

Acked-by: Borislav Petkov (AMD) <[email protected]>

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

2024-02-09 00:23:14

by Sean Christopherson

Subject: Re: [PATCH] KVM: x86/emulator: emulate movbe with operand-size prefix

On Tue, 12 Dec 2023 10:59:37 +0100, Julian Stecklina wrote:
> The MOVBE instruction can come with an operand-size prefix (66h). In
> this, case the x86 emulation code returns EMULATION_FAILED.
>
> It turns out that em_movbe can already handle this case and all that
> is missing is an entry in respective opcode tables to populate
> gprefix->pfx_66.
>
> [...]

Applied to kvm-x86 misc, thanks! I have a KUT testcase for this now, I'll post
it at some point.

[1/1] KVM: x86/emulator: emulate movbe with operand-size prefix
https://github.com/kvm-x86/linux/commit/03f6298c7cf6

--
https://github.com/kvm-x86/linux/tree/next