[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [V9 1/3] x86/xsaves: enable xsaves/xrstors/xsavec in xen
On Thu, Nov 05, 2015 at 02:06:25AM -0700, Jan Beulich wrote: > >>> On 05.11.15 at 02:34, <shuai.ruan@xxxxxxxxxxxxxxx> wrote: > > On Wed, Nov 04, 2015 at 10:04:33AM -0700, Jan Beulich wrote: > >> >>> On 03.11.15 at 07:27, <shuai.ruan@xxxxxxxxxxxxxxx> wrote: > >> > @@ -158,6 +334,20 @@ void xsave(struct vcpu *v, uint64_t mask) > >> > case 4: case 2: > >> > - asm volatile ( "1: .byte 0x0f,0xae,0x2f\n" > >> > - ".section .fixup,\"ax\" \n" > >> > - "2: mov %5,%%ecx \n" > >> > - " xor %1,%1 \n" > >> > - " rep stosb \n" > >> > - " lea %2,%0 \n" > >> > - " mov %3,%1 \n" > >> > - " jmp 1b \n" > >> > - ".previous \n" > >> > - _ASM_EXTABLE(1b, 2b) > >> > - : "+&D" (ptr), "+&a" (lmask) > >> > - : "m" (*ptr), "g" (lmask), "d" (hmask), > >> > - "m" (xsave_cntxt_size) > >> > - : "ecx" ); > >> > + alternative_input("1: "".byte 0x0f,0xae,0x2f", > >> > + ".byte 0x0f,0xc7,0x1f", > >> > + X86_FEATURE_XSAVES, > >> > + "D" (ptr), "m" (*ptr), "a" (lmask), "d" > > (hmask)); > >> > + asm volatile (XSTATE_FIXUP); > >> > break; > >> > } > >> > } > >> > +#undef XSTATE_FIXUP > >> > >> Repeating my comment on v8: "I wonder whether at least for the > >> restore side alternative asm wouldn't result in better readable code > >> and at the same time in a smaller patch." Did you at least look into > >> that option? > >> > > I may misunderstand your meaning. I have adressed the comment by changing > > the restor side using alternative_input. Does "alternative_input" not what > > you want ? > > if it is not what you want, please give me some suggestions how to > > address this ? > > Oh, I'm sorry, I should have looked more closely. The fact that > XSTATE_FIXUP survived made me draw wrong conclusions without > looking more closely. Now the bad news is - you can't split things > like this, as the compiler doesn't make any guarantees as to > register values between two asm()-s. The whole construct needs > to and up as a single asm(), which is why XSTATE_FIXUP and is > unlikely to be of much use here (at least in the context of this > patch; a separate cleanup patch might eliminate the redundancy). > Ok. So alternative_input will not used here (means use the way xrstor in Patch 8)? Or put the XSTATE_FIXUP into alternative_input ? Which one is ok to you ? Thanks > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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