Re: [tip: x86/pasid] x86/asm: Carve out a generic movdir64b() helper for general usage
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- Subject: Re: [tip: x86/pasid] x86/asm: Carve out a generic movdir64b() helper for general usage
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Thu, 8 Oct 2020 08:49:28 +0200
- Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-tip-commits@xxxxxxxxxxxxxxx, Michael Matz <matz@xxxxxxx>, Dave Jiang <dave.jiang@xxxxxxxxx>, Borislav Petkov <bp@xxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, x86 <x86@xxxxxxxxxx>, hjl.tools@xxxxxxxxx, linux-toolchains@xxxxxxxxxxxxxxx
- In-reply-to: <20201007211327.GN5607@zn.tnic>
- References: <20201005151126.657029-2-dave.jiang@intel.com> <160208728972.7002.18130814269550766361.tip-bot2@tip-bot2> <20201007170835.GM2628@hirez.programming.kicks-ass.net> <20201007211327.GN5607@zn.tnic>
On Wed, Oct 07, 2020 at 11:13:27PM +0200, Borislav Petkov wrote:
> 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@xxxxxxxxxxxxx
That, 100x that. Why wasn't it fixed then? How about we fix binutils to
accept the sane mnemonic as well?
> > 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:
Then we'll just keep the byte code around until we reach the min
binutils that's sane, but at least we can fix the comment to not be
insane.
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