From: Gleb Natapov <gleb@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: kvm@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, mingo@elte.hu,
a.p.zijlstra@chello.nl, tglx@linutronix.de, hpa@zytor.com,
riel@redhat.com, cl@linux-foundation.org, mtosatti@redhat.com
Subject: Re: [PATCH v6 08/12] Handle async PF in a guest.
Date: Sun, 10 Oct 2010 09:56:25 +0200 [thread overview]
Message-ID: <20101010075625.GM2397@redhat.com> (raw)
In-Reply-To: <4CB0B8EF.3050702@redhat.com>
On Sat, Oct 09, 2010 at 08:48:15PM +0200, Avi Kivity wrote:
> On 10/07/2010 08:03 PM, Gleb Natapov wrote:
> >> >>
> >> >Host side keeps track of outstanding apfs and will not send apf for the
> >> >same phys address twice. It will halt vcpu instead.
> >>
> >> What about different pages, running the scheduler code?
> >>
> >We can get couple of nested apfs, just like we can get nested
> >interrupts. Since scheduler disables preemption second apf will halt.
>
> How much is a couple?
>
> Consider:
>
> SIGSTOP
> Entire process swapped out
> SIGCONT
>
> We can get APF's on the current code, the scheduler code, the stack,
> any debugging code in between (e.g. ftrace), and the page tables for
> all of these.
>
Lets count them all. Suppose guest is in a userspace process code and
guest memory is completely swapped out. Guest starts to run and faults
in userspace. Apf is queued but can't be delivered due to faults in
idt and exception stack. All of them will be taken synchronously due
to event pending check. After apf is delivered any fault in apf code
will be takes synchronously since interrupt are disabled. Just before
calling schedule() interrupts are enabled, so next pf that will happen
during call to schedule() will be taken asynchronously. Which will cause
another call to schedule() at which point vcpu will be halted since two
apfs happened at the same address. So I counted two of them.
--
Gleb.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2010-10-10 7:56 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-04 15:56 [PATCH v6 00/12] KVM: Add host swap event notifications for PV guest Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 01/12] Add get_user_pages() variant that fails if major fault is required Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 02/12] Halt vcpu if page it tries to access is swapped out Gleb Natapov
2010-10-05 1:20 ` Rik van Riel
2010-10-05 14:59 ` Marcelo Tosatti
2010-10-06 10:50 ` Avi Kivity
2010-10-06 10:52 ` Gleb Natapov
2010-10-07 9:54 ` Avi Kivity
2010-10-07 17:48 ` Gleb Natapov
2010-10-06 11:15 ` Gleb Natapov
2010-10-07 9:50 ` Avi Kivity
2010-10-07 9:52 ` Avi Kivity
2010-10-07 13:24 ` Rik van Riel
2010-10-07 13:29 ` Avi Kivity
2010-10-07 17:47 ` Gleb Natapov
2010-10-09 18:30 ` Avi Kivity
2010-10-09 18:32 ` Avi Kivity
2010-10-10 7:30 ` Gleb Natapov
2010-10-10 7:29 ` Gleb Natapov
2010-10-10 15:55 ` Avi Kivity
2010-10-10 15:56 ` Avi Kivity
2010-10-10 16:17 ` Gleb Natapov
2010-10-10 16:16 ` Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 03/12] Retry fault before vmentry Gleb Natapov
2010-10-05 15:54 ` Marcelo Tosatti
2010-10-06 11:07 ` Gleb Natapov
2010-10-06 14:20 ` Marcelo Tosatti
2010-10-07 18:44 ` Gleb Natapov
2010-10-08 16:07 ` Marcelo Tosatti
2010-10-07 12:29 ` Avi Kivity
2010-10-07 17:21 ` Gleb Natapov
2010-10-09 18:42 ` Avi Kivity
2010-10-10 7:35 ` Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 04/12] Add memory slot versioning and use it to provide fast guest write interface Gleb Natapov
2010-10-05 1:29 ` Rik van Riel
2010-10-05 16:57 ` Marcelo Tosatti
2010-10-06 11:14 ` Gleb Natapov
2010-10-06 14:38 ` Marcelo Tosatti
2010-10-06 20:08 ` Gleb Natapov
2010-10-07 10:00 ` Avi Kivity
2010-10-07 15:42 ` Marcelo Tosatti
2010-10-07 16:03 ` Gleb Natapov
2010-10-07 16:20 ` Avi Kivity
2010-10-07 17:23 ` Gleb Natapov
2010-10-10 12:48 ` Avi Kivity
2010-10-07 12:31 ` Avi Kivity
2010-10-04 15:56 ` [PATCH v6 05/12] Move kvm_smp_prepare_boot_cpu() from kvmclock.c to kvm.c Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 06/12] Add PV MSR to enable asynchronous page faults delivery Gleb Natapov
2010-10-07 12:42 ` Avi Kivity
2010-10-07 17:53 ` Gleb Natapov
2010-10-10 12:47 ` Avi Kivity
2010-10-10 13:27 ` Gleb Natapov
2010-10-07 12:58 ` Avi Kivity
2010-10-07 17:59 ` Gleb Natapov
2010-10-09 18:43 ` Avi Kivity
2010-10-04 15:56 ` [PATCH v6 07/12] Add async PF initialization to PV guest Gleb Natapov
2010-10-05 2:34 ` Rik van Riel
2010-10-05 18:25 ` Marcelo Tosatti
2010-10-06 10:55 ` Gleb Natapov
2010-10-06 14:45 ` Marcelo Tosatti
2010-10-06 20:05 ` Gleb Natapov
2010-10-07 12:50 ` Avi Kivity
2010-10-08 7:54 ` Gleb Natapov
2010-10-09 18:44 ` Avi Kivity
2010-10-04 15:56 ` [PATCH v6 08/12] Handle async PF in a guest Gleb Natapov
2010-10-07 13:10 ` Avi Kivity
2010-10-07 17:14 ` Gleb Natapov
2010-10-07 17:18 ` Avi Kivity
2010-10-07 17:48 ` Rik van Riel
2010-10-07 18:03 ` Gleb Natapov
2010-10-09 18:48 ` Avi Kivity
2010-10-10 7:56 ` Gleb Natapov [this message]
2010-10-10 12:40 ` Avi Kivity
2010-10-10 12:32 ` Gleb Natapov
2010-10-10 12:38 ` Avi Kivity
2010-10-10 13:22 ` Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 09/12] Inject asynchronous page fault into a PV guest if page is swapped out Gleb Natapov
2010-10-05 2:36 ` Rik van Riel
2010-10-05 19:00 ` Marcelo Tosatti
2010-10-06 10:42 ` Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 10/12] Handle async PF in non preemptable context Gleb Natapov
2010-10-05 19:51 ` Marcelo Tosatti
2010-10-06 10:41 ` Gleb Natapov
2010-10-10 14:25 ` Gleb Natapov
2010-10-04 15:56 ` [PATCH v6 11/12] Let host know whether the guest can handle async PF in non-userspace context Gleb Natapov
2010-10-07 13:36 ` Avi Kivity
2010-10-04 15:56 ` [PATCH v6 12/12] Send async PF when guest is not in userspace too Gleb Natapov
2010-10-05 2:37 ` Rik van Riel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20101010075625.GM2397@redhat.com \
--to=gleb@redhat.com \
--cc=a.p.zijlstra@chello.nl \
--cc=avi@redhat.com \
--cc=cl@linux-foundation.org \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@elte.hu \
--cc=mtosatti@redhat.com \
--cc=riel@redhat.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).