lkml.org 
[lkml]   [2012]   [Sep]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 2/8] KVM: x86 emulator: use aligned variants of SSE register ops
    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


    \
     
     \ /
      Last update: 2012-09-04 15:03    [W:0.028 / U:0.420 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site