From: "Michael S. Tsirkin" <mst@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Gleb Natapov <gleb@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
x86@kernel.org, kvm@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>, Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC dontapply 5/5] kvm_para: guest side for eoi avoidance
Date: Tue, 8 May 2012 19:57:36 +0300 [thread overview]
Message-ID: <20120508165736.GA26795@redhat.com> (raw)
In-Reply-To: <4FA93FA3.20306@zytor.com>
On Tue, May 08, 2012 at 08:45:39AM -0700, H. Peter Anvin wrote:
> On 05/08/2012 08:28 AM, Gleb Natapov wrote:
> > On Tue, May 08, 2012 at 05:26:55PM +0200, Paolo Bonzini wrote:
> >> Il 23/04/2012 16:04, Michael S. Tsirkin ha scritto:
> >>> +/* Our own copy of __test_and_clear_bit to make sure
> >>> + * it is done with a single instruction */
> >>
> >> Is this for microoptimization or correctness? If the latter, it does
> >> not ensure anything without a "lock" prefix.
> >>
> > It can't race with other vcpus, only with vmexit on the same vcpu.
> >
>
> That doesn't answer the question very well... I really don't understand
> the point of having a private copy here.
>
> I really, really don't want a bunch of private interfaces around. It
> would be a lot better to define a test_and_{set,clear}_bit_local() in
> <asm/bitops.h> which is defined to be local CPU atomic.
>
> -hpa
Will do. OK to only define them for x86 for now?
They would be unused on other arches even if I defined them ...
> --
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2012-05-08 17:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 14:03 [PATCH RFC 0/5] apic: eoi optimization support Michael S. Tsirkin
2012-04-23 14:04 ` [PATCH RFC 1/5] apic: fix typo EIO_ACK -> EOI_ACK and document Michael S. Tsirkin
2012-04-23 14:04 ` [PATCH RFC 2/5] apic: use symbolic APIC_EOI_ACK Michael S. Tsirkin
2012-04-23 14:04 ` [PATCH RFC 3/5] x86: add apic->eoi_write callback Michael S. Tsirkin
2012-04-23 14:04 ` [PATCH RFC 4/5] x86: eoi micro-optimization Michael S. Tsirkin
2012-04-23 14:04 ` [PATCH RFC dontapply 5/5] kvm_para: guest side for eoi avoidance Michael S. Tsirkin
2012-04-24 6:50 ` Gleb Natapov
2012-04-24 6:58 ` Michael S. Tsirkin
2012-04-24 7:07 ` Gleb Natapov
2012-05-08 15:26 ` Paolo Bonzini
2012-05-08 15:28 ` Gleb Natapov
2012-05-08 15:45 ` H. Peter Anvin
2012-05-08 16:32 ` Gleb Natapov
2012-05-08 16:57 ` Michael S. Tsirkin [this message]
2012-05-08 18:06 ` H. Peter Anvin
2012-05-08 19:36 ` Michael S. Tsirkin
2012-05-07 10:35 ` [PATCH RFC 0/5] apic: eoi optimization support Ingo Molnar
2012-05-07 10:59 ` Michael S. Tsirkin
2012-05-07 11:40 ` Ingo Molnar
2012-05-07 11:47 ` Avi Kivity
2012-05-07 11:57 ` Ingo Molnar
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