linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Avi Kivity <avi@redhat.com>
To: Mathias Krause <minipli@googlemail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/8] KVM: x86 emulator: use aligned variants of SSE register ops
Date: Tue, 04 Sep 2012 15:09:42 +0300	[thread overview]
Message-ID: <5045EF86.4080600@redhat.com> (raw)
In-Reply-To: <1346283020-22385-3-git-send-email-minipli@googlemail.com>

On 08/30/2012 02:30 AM, Mathias Krause wrote:
> As the the compiler ensures that the memory operand is always aligned
> to a 16 byte memory location, 

I'm not sure it does.  Is V4SI aligned?  Do we use alignof() to
propagate the alignment to the vcpu allocation code?

> use the aligned variant of MOVDQ for
> read_sse_reg() and write_sse_reg().
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 1451cff..5a0fee1 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -909,23 +909,23 @@ static void read_sse_reg(struct x86_emulate_ctxt *ctxt, sse128_t *data, int reg)
>  {
>  	ctxt->ops->get_fpu(ctxt);
>  	switch (reg) {
> -	case 0: asm("movdqu %%xmm0, %0" : "=m"(*data)); break;
> -	case 1: asm("movdqu %%xmm1, %0" : "=m"(*data)); break;
> -	case 2: asm("movdqu %%xmm2, %0" : "=m"(*data)); break;
> -	case 3: asm("movdqu %%xmm3, %0" : "=m"(*data)); break;
> -	case 4: asm("movdqu %%xmm4, %0" : "=m"(*data)); break;
> -	case 5: asm("movdqu %%xmm5, %0" : "=m"(*data)); break;
> -	case 6: asm("movdqu %%xmm6, %0" : "=m"(*data)); break;
> -	case 7: asm("movdqu %%xmm7, %0" : "=m"(*data)); break;
> +	case 0: asm("movdqa %%xmm0, %0" : "=m"(*data)); break;
> +	case 1: asm("movdqa %%xmm1, %0" : "=m"(*data)); break;
> +	case 2: asm("movdqa %%xmm2, %0" : "=m"(*data)); break;
> +	case 3: asm("movdqa %%xmm3, %0" : "=m"(*data)); break;
> +	case 4: asm("movdqa %%xmm4, %0" : "=m"(*data)); break;
> +	case 5: asm("movdqa %%xmm5, %0" : "=m"(*data)); break;
> +	case 6: asm("movdqa %%xmm6, %0" : "=m"(*data)); break;
> +	case 7: asm("movdqa %%xmm7, %0" : "=m"(*data)); break;
>  #ifdef CONFIG_X86_64
> -	case 8: asm("movdqu %%xmm8, %0" : "=m"(*data)); break;
> -	case 9: asm("movdqu %%xmm9, %0" : "=m"(*data)); break;
> -	case 10: asm("movdqu %%xmm10, %0" : "=m"(*data)); break;
> -	case 11: asm("movdqu %%xmm11, %0" : "=m"(*data)); break;
> -	case 12: asm("movdqu %%xmm12, %0" : "=m"(*data)); break;
> -	case 13: asm("movdqu %%xmm13, %0" : "=m"(*data)); break;
> -	case 14: asm("movdqu %%xmm14, %0" : "=m"(*data)); break;
> -	case 15: asm("movdqu %%xmm15, %0" : "=m"(*data)); break;
> +	case 8: asm("movdqa %%xmm8, %0" : "=m"(*data)); break;
> +	case 9: asm("movdqa %%xmm9, %0" : "=m"(*data)); break;
> +	case 10: asm("movdqa %%xmm10, %0" : "=m"(*data)); break;
> +	case 11: asm("movdqa %%xmm11, %0" : "=m"(*data)); break;
> +	case 12: asm("movdqa %%xmm12, %0" : "=m"(*data)); break;
> +	case 13: asm("movdqa %%xmm13, %0" : "=m"(*data)); break;
> +	case 14: asm("movdqa %%xmm14, %0" : "=m"(*data)); break;
> +	case 15: asm("movdqa %%xmm15, %0" : "=m"(*data)); break;
>  #endif
>  	default: BUG();


The vmexit costs dominates any win here by several orders of magnitude.


-- 
error compiling committee.c: too many arguments to function

  reply	other threads:[~2012-09-04 12:09 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-29 23:30 [PATCH 0/8] KVM: minor cleanups and optimizations Mathias Krause
2012-08-29 23:30 ` [PATCH 1/8] KVM: x86: minor size optimization Mathias Krause
2012-08-29 23:30 ` [PATCH 2/8] KVM: x86 emulator: use aligned variants of SSE register ops Mathias Krause
2012-09-04 12:09   ` Avi Kivity [this message]
2012-09-04 12:13     ` Avi Kivity
2012-09-04 12:51       ` Mathias Krause
2012-09-05  9:43         ` Avi Kivity
2012-08-29 23:30 ` [PATCH 3/8] KVM: x86: mark opcode tables const Mathias Krause
2012-08-29 23:30 ` [PATCH 4/8] KVM: x86: constify emulate_ops Mathias Krause
2012-08-29 23:30 ` [PATCH 5/8] KVM: x86: constify read_write_emulator_ops Mathias Krause
2012-08-29 23:30 ` [PATCH 6/8] KVM: x86: more constification Mathias Krause
2012-08-29 23:30 ` [PATCH 7/8] KVM: VMX: constify lookup tables Mathias Krause
2012-08-29 23:30 ` [PATCH 8/8] KVM: SVM: " Mathias Krause

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5045EF86.4080600@redhat.com \
    --to=avi@redhat.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=minipli@googlemail.com \
    --cc=mtosatti@redhat.com \
    --subject='Re: [PATCH 2/8] KVM: x86 emulator: use aligned variants of SSE register ops' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).