linux-kernel - Re: [PATCH V3 01/23] perf/x86: Support outputting XMM registers

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Date:   Fri, 22 Mar 2019 10:22:50 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     kan.liang@...ux.intel.com, acme@...nel.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, jolsa@...nel.org,
        eranian@...gle.com, alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH V3 01/23] perf/x86: Support outputting XMM registers

> > 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.

> 
> > +	/* 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,
> >  };
> >  #endif /* _ASM_X86_PERF_REGS_H */
> 
> Also, what happens if we run a 32bit kernel or 32bit compat task?
> 
> Then the register dump will report PERF_SAMPLE_REGS_ABI_32, should we
> then still interpret the XMM registers as 2x64bit?

Yes XMM registers are 128bit in 32bit mode too.

> 
> Are they still at the same offset?

Yes.

> 
> Do we need additional PERF_SAMPLE_REGS_ABI_* definitions for this?

I don't think so.

-Andi