From: Paolo Bonzini <pbonzini@redhat.com>
To: alvise rigo <a.rigo@virtualopensystems.com>,
Peter Maydell <peter.maydell@linaro.org>
Cc: "MTTCG Devel" <mttcg@listserver.greensocs.com>,
"Mark Burton" <mark.burton@greensocs.com>,
"Claudio Fontana" <claudio.fontana@huawei.com>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Jani Kokkonen" <jani.kokkonen@huawei.com>,
"tech@virtualopensystems.com" <tech@virtualopensystems.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"KONRAD Frédéric" <fred.konrad@greensocs.com>
Subject: Re: [Qemu-devel] [mttcg] cputlb: Use async tlb_flush_by_mmuidx
Date: Mon, 29 Feb 2016 15:06:33 +0100 [thread overview]
Message-ID: <56D45069.8090206@redhat.com> (raw)
In-Reply-To: <CAH47eN1Vqy3KLnk9zBTUqAHbA1mnOMc3X1LMqjWXvgaByinB1Q@mail.gmail.com>
On 29/02/2016 15:02, alvise rigo wrote:
> > Yeah, that's the other approach -- really split the things that can
> > be async and do real "wait for completion" at points which must
> > synchronize. (Needs a little care since DMB is not the only such point.)
> > An initial implementation that does an immediate wait-for-completion
> > is probably simpler to review though, and add the real asynchrony
> > later. And either way you need an API for the target to wait for
> > completion.
> OK, so basically being sure that the target CPU performs the flush
> before executing the next TB is not enough. We need a sort of feedback
> that the flush has been done before emulating the next guest
> instruction. Did I get it right?
That risks getting deadlocks if CPU A asks B to flush the TLB and vice
versa. Using a halted state means that the VCPU thread goes through the
cpus.c loop and can for example service other CPUs' TLB flush requests.
Paolo
next prev parent reply other threads:[~2016-02-29 14:06 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 13:16 [Qemu-devel] [mttcg] cputlb: Use async tlb_flush_by_mmuidx Alvise Rigo
2016-02-29 13:21 ` Peter Maydell
2016-02-29 13:50 ` Paolo Bonzini
2016-02-29 13:55 ` Peter Maydell
2016-02-29 14:02 ` alvise rigo
2016-02-29 14:06 ` Paolo Bonzini [this message]
2016-02-29 14:18 ` alvise rigo
2016-03-04 14:28 ` alvise rigo
2016-03-07 20:18 ` Alex Bennée
2016-03-07 21:18 ` Paolo Bonzini
2016-03-11 11:08 ` alvise rigo
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