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Groups > linux.kernel > #1464845
| From | Linus Torvalds <torvalds@linux-foundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: RFC: Petition Intel/AMD to add POPF_IF insn |
| Date | 2016-08-18 00:40 +0200 |
| Message-ID | <s7hF8-7AW-7@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <s7eQV-5ow-7@gated-at.bofh.it> <s7eQV-5ow-23@gated-at.bofh.it> <s7gzo-6R5-31@gated-at.bofh.it> <s7gJ4-6VE-43@gated-at.bofh.it> <s7gSK-6Zu-23@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Wed, Aug 17, 2016 at 2:43 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>
> It shouldn't be *too* bad, since xen_restore_fl only affects "IF".
> And even if native_restore_fl needs to be able to turn IRQs off as
> well as on, we can just do:
>
> if (likely(flags & X86_EFLAGS_IF))
> sti();
> else
> cli();
>
> at some cost to code size but hopefully little to no runtime cost for
> the sane cases.
No, that would be horrible for the case where we had an irq spinlock
in an irq-region. Then we'd have a pointless "cli" there.
So I'd rather just make sure that only the spinlock code actually uses
native_restore_fl().
And yes, the patch works at least minimally, since I'm writing this
with a kernel compiled with that.
Of course, somebody really should do timings on modern CPU's (in cpl0,
comparing native_fl() that enables interrupts with a popf)
Linus
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RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-17 19:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 20:00 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-17 21:00 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Andy Lutomirski <luto@amacapital.net> - 2016-08-17 21:20 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-17 21:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-17 21:40 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 22:00 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 21:40 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 23:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 23:40 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Andy Lutomirski <luto@amacapital.net> - 2016-08-17 23:50 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-18 00:40 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-18 15:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-19 03:00 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-19 03:10 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-19 04:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Paolo Bonzini <pbonzini@redhat.com> - 2016-08-19 13:00 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-18 11:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-18 14:20 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Paolo Bonzini <pbonzini@redhat.com> - 2016-08-19 04:10 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 21:50 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-17 21:30 +0200
Re: RFC: Petition Intel/AMD to add POPF_IF insn Denys Vlasenko <dvlasenk@redhat.com> - 2016-08-17 20:40 +0200
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