Re: [Xen-devel] [V9 1/3] x86/xsaves: enable xsaves/xrstors/xsavec in xen

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

On Thu, Nov 05, 2015 at 03:13:01AM -0700, Jan Beulich wrote:
> >>> On 05.11.15 at 10:57, <shuai.ruan@xxxxxxxxxxxxxxx> wrote:
> > 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 ?
> 
> The latter, if necessary by extending alternative_input() accordingly
> (or provide a second, more flexible variant if need be; iirc Linux has
> gained a couple of variants over the years).
> 
Ok,I will introduct 2 new macro to handle this. 

1. #define ASM_OUTPUT2(a...) a
The first one(Porting from linux) is used when more than one output parameter 
is needed.

2. #define alternative_io_fixup(oldinstr, newinstr, feature, fixup, output, 
input...)           \
        asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) "\n"     \
        fixup                                                           \
        : output : "i"(0), ## input)

The second is to handle alternaive asm with fixup. 

Then xrstor side will be:
alternative_io_fixup("1: "".byte 0x48,0x0f,0xae,0x2f",
                          ".byte 0x48,0x0f,0xc7,0x1f",
                          X86_FEATURE_XSAVES,
                          XSTATE_FIXUP,
                          ASM_OUTPUT2("+&D" (ptr), "+&a" (lmask)),
                          "m" (*ptr), "g" (lmask), "d" (hmask), 
                          "m" (xsave_cntxt_size) : "ecx");

Also, the position of the operand used in  XSTATE_FIXUP will
changed.
Any suggestions of this ?

Thanks
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
> 

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