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SubjectRe: [PATCH V3 01/23] perf/x86: Support outputting XMM registers
On Mon, 25 Mar 2019, Liang, Kan wrote:
> On 3/23/2019 5:56 AM, Peter Zijlstra wrote:
> > On Fri, Mar 22, 2019 at 10:22:50AM -0700, Andi Kleen wrote:
> > > > > diff --git a/arch/x86/include/uapi/asm/perf_regs.h
> > > > > b/arch/x86/include/uapi/asm/perf_regs.h
> > > > > index f3329cabce5c..b33995313d17 100644
> > > > > --- a/arch/x86/include/uapi/asm/perf_regs.h
> > > > > +++ b/arch/x86/include/uapi/asm/perf_regs.h
> > > > > @@ -28,7 +28,29 @@ enum perf_event_x86_regs {
> > > > > PERF_REG_X86_R14,
> > > > > PERF_REG_X86_R15,
> > > > > - PERF_REG_X86_32_MAX = PERF_REG_X86_GS + 1,
> > > > > - PERF_REG_X86_64_MAX = PERF_REG_X86_R15 + 1,
> > > >
> > > > So this changes UAPI visible symbols... did we think about that?
> > >
> > > Should be fine. Old programs won't use the new bits,
> > > and it just uses not yet used bits.
> >
> > Old programs (that used the above symbols) will now fail to compile.
> > Even if they won't use the new bits, that seems like a bad thing.
> >
>
> Yes, other programs which use the PERF_REG_GPR_X86_32/64_MAX symbols should be
> broken.
> I think the new name PERF_REG_GPR_X86_32/64_MAX are more accurate. So I will
> keep both names in V4, and add comments for the old names.
>
> /*
> * These names are deprecated, please use new names as below to instead.

This is a pointless exercise. You can call them deprecated, but you cannot
remove them by any means. It's a userspace ABI. End of story.

> * PERF_REG_GPR_X86_32_MAX
> * PERF_REG_GPR_X86_64_MAX

Just keep the ones we have without adding new ones and just add a comment
that these are the limits for the GPRs.

> */
> PERF_REG_X86_32_MAX = PERF_REG_X86_GS + 1,
> PERF_REG_X86_64_MAX = PERF_REG_X86_R15 + 1,
>
>
> > > > > + /* These all need two bits set because they are 128bit */
> > > > > + PERF_REG_X86_XMM0 = 32,
> > > > > + PERF_REG_X86_XMM1 = 34,
> > > > > + PERF_REG_X86_XMM2 = 36,
> > > > > + PERF_REG_X86_XMM3 = 38,
> > > > > + PERF_REG_X86_XMM4 = 40,
> > > > > + PERF_REG_X86_XMM5 = 42,
> > > > > + PERF_REG_X86_XMM6 = 44,
> > > > > + PERF_REG_X86_XMM7 = 46,
> > > > > + PERF_REG_X86_XMM8 = 48,
> > > > > + PERF_REG_X86_XMM9 = 50,
> > > > > + PERF_REG_X86_XMM10 = 52,
> > > > > + PERF_REG_X86_XMM11 = 54,
> > > > > + PERF_REG_X86_XMM12 = 56,
> > > > > + PERF_REG_X86_XMM13 = 58,
> > > > > + PERF_REG_X86_XMM14 = 60,
> > > > > + PERF_REG_X86_XMM15 = 62,
> > > > > +
> > > > > + /* This does not include the XMMX registers */
> > > > > + PERF_REG_GPR_X86_32_MAX = PERF_REG_X86_GS + 1,
> > > > > + PERF_REG_GPR_X86_64_MAX = PERF_REG_X86_R15 + 1,
> > > > > +
> > > > > + /* All registers include the XMMX registers */
> > > > > + PERF_REG_X86_MAX = PERF_REG_X86_XMM15 + 2,

And this wants to be PERF_REG_X86_XMM_MAX so you won't run into the same
trouble when yet another register set has to be added.

Thanks,

tglx

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