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Subject: Re: RFC: Petition Intel/AMD to add POPF_IF insn
To: Linus Torvalds <torvalds@linux-foundation.org>,
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 19 Aug 2016 12:54:39 +0200
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On 18/08/2016 19:24, Linus Torvalds wrote:
>> > I didn't do CPL0 tests yet. Realized that cli/sti can be tested in userspace
>> > if we set iopl(3) first.
> Yes, but it might not be the same. So the timings could be very
> different from a cpl0 case.

FWIW I recently measured around 20 cycles for a popf as well on
Haswell-EP and CPL=0 (that was for commit f2485b3e0c6c, "KVM: x86: use
guest_exit_irqoff", 2016-07-01).

Paolo