Messages in this thread | ![/](/images/icornerl.gif) | | From | Uros Bizjak <> | Date | Fri, 28 Aug 2020 08:41:18 +0200 | Subject | Re: [PATCH v2] x86: Use xorl %0,%0 in __get_user_asm |
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On Thu, Aug 27, 2020 at 10:14 PM Al Viro <viro@zeniv.linux.org.uk> wrote: > > On Thu, Aug 27, 2020 at 08:09:04PM +0200, Uros Bizjak wrote: > > xorl %0,%0 is equivalent to xorq %0,%0 as both will zero the > > entire register. Use xorl %0,%0 for all operand sizes to avoid > > REX prefix byte when legacy registers are used and to avoid size > > prefix byte when 16bit registers are used. > > > > Zeroing the full register is OK in this use case. xorl %0,%0 also > > breaks register dependency chains, avoiding potential partial > > register stalls with 8 and 16bit operands. > > No objections, but talking about stalls is more than slightly > ridiculous - we'd just taken a #PF, failed there, flipped > pt_regs %rip to fixup section, returned from fault and are > about to fail whatever syscall that had been; a stall here > is really not an issue...
Should I submit a v3 with the offending sentence removed, or could I just ask a committer to remove it on the fly?
Uros.
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