linux-kernel - Re: [PATCH v2] x86: insn: Add insn_is

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Date:   Thu, 9 Apr 2020 16:45:46 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Christian König <christian.koenig@....com>,
        Jann Horn <jannh@...gle.com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>, amd-gfx@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>,
        David Zhou <David1.Zhou@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v2] x86: insn: Add insn_is_fpu()

On Thu, Apr 09, 2020 at 04:32:12PM +0200, Peter Zijlstra wrote:
> On Thu, Apr 09, 2020 at 01:09:11AM +0900, Masami Hiramatsu wrote:
> > Add insn_is_fpu(insn) which tells that the insn is
> > whether touch the FPU/SSE/MMX register or the instruction
> > of FP coprocessor.
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > ---
> 
> Sadly, it turns out I need "FWAIT" too, which I tried adding like the
> below, but that comes apart most mighty :/
> 
> The trouble is that FWAIT doesn't take a MODRM, so the previous
> assumption that INAT_FPU implied INAT_MODRM needs to be broken, and I
> think that ripples through somewhere.
> 
> (also, your patch adds some whitespace to convert_operands(), not sure
> that was intended)
> 
> --- a/arch/x86/lib/x86-opcode-map.txt
> +++ b/arch/x86/lib/x86-opcode-map.txt
> @@ -206,7 +206,7 @@ Table: one byte opcode
>  98: CBW/CWDE/CDQE
>  99: CWD/CDQ/CQO
>  9a: CALLF Ap (i64)
> -9b: FWAIT/WAIT
> +9b: FWAIT/WAIT {FPU}
>  9c: PUSHF/D/Q Fv (d64)
>  9d: POPF/D/Q Fv (d64)
>  9e: SAHF
> --- a/arch/x86/tools/gen-insn-attr-x86.awk
> +++ b/arch/x86/tools/gen-insn-attr-x86.awk
> @@ -331,9 +331,13 @@ function convert_operands(count,opnd,
>  		if (match(opcode, rex_expr))
>  			flags = add_flags(flags, "INAT_MAKE_PREFIX(INAT_PFX_REX)")
>  
> +		# check coprocessor escape
> +		if (match(ext, "^ESC"))
> +			flags = add_flags(flags, "INAT_MODRM")

I'm an idiot; that needs to be:

		if (match(opcode, "^ESC"))

> +
>  		# check FPU/MMX/SSE superscripts
>  		if (match(ext, fpu_expr))
> -			flags = add_flags(flags, "INAT_MODRM | INAT_FPU")
> +			flags = add_flags(flags, "INAT_FPU")
>  
>  		# check VEX codes
>  		if (match(ext, evexonly_expr))