Re: [PATCH] KVM: x86: Introduce segmented_write_std

[Paolo Bonzini <pbonzini@redhat.com>]

----- Original Message -----
> From: "Steve Rutherford" <srutherford@google.com>
> To: kvm@vger.kernel.org
> Cc: pbonzini@redhat.com, dvyukov@google.com, rkrcmar@redhat.com, ppandit@redhat.com, kernellwp@gmail.com
> Sent: Thursday, January 12, 2017 3:28:29 AM
> Subject: [PATCH] KVM: x86: Introduce segmented_write_std
> 
> Introduces segemented_write_std.
> 
> Switches from emulated reads/writes to standard read/writes in fxsave,
> fxrstor, sgdt, and sidt.
> 
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Steve Rutherford <srutherford@google.com>
> ---
>  arch/x86/kvm/emulate.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 2b8349a2b14b..ad258aa0b302 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -819,6 +819,20 @@ static int segmented_read_std(struct x86_emulate_ctxt
> *ctxt,
>  	return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception);
>  }
>  
> +static int segmented_write_std(struct x86_emulate_ctxt *ctxt,
> +			       struct segmented_address addr,
> +			       void *data,
> +			       unsigned int size)
> +{
> +	int rc;
> +	ulong linear;
> +
> +	rc = linearize(ctxt, addr, size, true, &linear);
> +	if (rc != X86EMUL_CONTINUE)
> +		return rc;
> +	return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception);
> +}
> +
>  /*
>   * Prefetch the remaining bytes of the instruction without crossing page
>   * boundary if they are not in fetch_cache yet.
> @@ -3686,8 +3700,8 @@ static int emulate_store_desc_ptr(struct
> x86_emulate_ctxt *ctxt,
>  	}
>  	/* Disable writeback. */
>  	ctxt->dst.type = OP_NONE;
> -	return segmented_write(ctxt, ctxt->dst.addr.mem,
> -			       &desc_ptr, 2 + ctxt->op_bytes);
> +	return segmented_write_std(ctxt, ctxt->dst.addr.mem,
> +				   &desc_ptr, 2 + ctxt->op_bytes);
>  }
>  
>  static int em_sgdt(struct x86_emulate_ctxt *ctxt)
> @@ -3933,7 +3947,7 @@ static int em_fxsave(struct x86_emulate_ctxt *ctxt)
>  	else
>  		size = offsetof(struct fxregs_state, xmm_space[0]);
>  
> -	return segmented_write(ctxt, ctxt->memop.addr.mem, &fx_state, size);
> +	return segmented_write_std(ctxt, ctxt->memop.addr.mem, &fx_state, size);
>  }
>  
>  static int fxrstor_fixup(struct x86_emulate_ctxt *ctxt,
> @@ -3975,7 +3989,7 @@ static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
>  	if (rc != X86EMUL_CONTINUE)
>  		return rc;
>  
> -	rc = segmented_read(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
> +	rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
>  	if (rc != X86EMUL_CONTINUE)
>  		return rc;
>  
> --
> 2.11.0.390.gc69c2f50cf-goog
> 
> 

Queued for 4.10, thanks.  At least fxsave/fxrstor is not in any
released version, but that was close.  I owe Dmitry some (more) beer.

Paolo