linux-kernel - Re: [tip: x86/pasid] x86/asm: Carve out a generic movdir64b() helper for general usage

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Message-ID: <20201007211327.GN5607@zn.tnic>
Date:   Wed, 7 Oct 2020 23:13:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        Michael Matz <matz@...e.de>, Dave Jiang <dave.jiang@...el.com>,
        Borislav Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
        x86 <x86@...nel.org>
Subject: Re: [tip: x86/pasid] x86/asm: Carve out a generic movdir64b() helper
 for general usage

On Wed, Oct 07, 2020 at 07:08:35PM +0200, Peter Zijlstra wrote:
> (%rdx), %rax, surely?

Right, later. Already tagged the branch so that Vinod can base stuff ontop.

> Also, that's a horrible convention, but I suppose (%rdx), (%rax) was
> out?

See the end of this mail:

https://lkml.kernel.org/r/alpine.LSU.2.20.2009241356020.20802@wotan.suse.de

> Can we pretty please get a binutils version that knows about this
> instruction, such that we know when we can get rid of the silly .byte
> encoded mess?

It looks like support for this insn got introduced in this binutils commit:

c0a30a9f0ab4 ("Enable Intel MOVDIRI, MOVDIR64B instructions")

So I guess from 2.31 onwards:

$ git tag --contains c0a30a9f0ab48
binutils-2_31
binutils-2_31_1
binutils-2_32
binutils-2_33
binutils-2_33_1
binutils-2_34
binutils-2_35
binutils-2_35_1
gdb-8.2-release
gdb-8.2.1-release
gdb-8.3-release
gdb-8.3.1-release
gdb-9.1-release
gdb-9.2-release
...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette