linux-kernel - Re: [PATCH RFC 4/5] x86: KVM: add xsetbv to the emulator

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Message-ID: <a86ca8b7-0333-398b-7bf6-90cb79366226@redhat.com>
Date:   Thu, 20 Jun 2019 14:18:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH RFC 4/5] x86: KVM: add xsetbv to the emulator

On 20/06/19 13:02, Vitaly Kuznetsov wrote:
> To avoid hardcoding xsetbv length to '3' we need to support decoding it in
> the emulator.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>

Can you also emulate it properly?  The code from QEMU's
target/i386/fpu_helper.c can help. :)

Paolo

> ---
>  arch/x86/include/asm/kvm_emulate.h | 1 +
>  arch/x86/kvm/emulate.c             | 9 ++++++++-
>  arch/x86/kvm/svm.c                 | 1 +
>  3 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
> index feab24cac610..478f76b0122d 100644
> --- a/arch/x86/include/asm/kvm_emulate.h
> +++ b/arch/x86/include/asm/kvm_emulate.h
> @@ -429,6 +429,7 @@ enum x86_intercept {
>  	x86_intercept_ins,
>  	x86_intercept_out,
>  	x86_intercept_outs,
> +	x86_intercept_xsetbv,
>  
>  	nr_x86_intercepts
>  };
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index d0d5dd44b4f4..ff25d94df684 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -4393,6 +4393,12 @@ static const struct opcode group7_rm1[] = {
>  	N, N, N, N, N, N,
>  };
>  
> +static const struct opcode group7_rm2[] = {
> +	N,
> +	DI(SrcNone | Priv, xsetbv),
> +	N, N, N, N, N, N,
> +};
> +
>  static const struct opcode group7_rm3[] = {
>  	DIP(SrcNone | Prot | Priv,		vmrun,		check_svme_pa),
>  	II(SrcNone  | Prot | EmulateOnUD,	em_hypercall,	vmmcall),
> @@ -4482,7 +4488,8 @@ static const struct group_dual group7 = { {
>  }, {
>  	EXT(0, group7_rm0),
>  	EXT(0, group7_rm1),
> -	N, EXT(0, group7_rm3),
> +	EXT(0, group7_rm2),
> +	EXT(0, group7_rm3),
>  	II(SrcNone | DstMem | Mov,		em_smsw, smsw), N,
>  	II(SrcMem16 | Mov | Priv,		em_lmsw, lmsw),
>  	EXT(0, group7_rm7),
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index f980fc43372d..39e61029f401 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6041,6 +6041,7 @@ static const struct __x86_intercept {
>  	[x86_intercept_ins]		= POST_EX(SVM_EXIT_IOIO),
>  	[x86_intercept_out]		= POST_EX(SVM_EXIT_IOIO),
>  	[x86_intercept_outs]		= POST_EX(SVM_EXIT_IOIO),
> +	[x86_intercept_xsetbv]		= PRE_EX(SVM_EXIT_XSETBV),
>  };
>  
>  #undef PRE_EX
>