From: Marcelo Tosatti <mtosatti@redhat.com>
To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Avi Kivity <avi@qumranet.com>, kvm-devel <kvm@vger.kernel.org>
Subject: Re: KVM: MMU: large page update_pte issue with non-PAE 32-bit guests
Date: Tue, 10 Jun 2008 13:44:50 -0300 [thread overview]
Message-ID: <20080610164450.GA4316@dmt.cnet> (raw)
In-Reply-To: <20080609223349.GQ8047@duo.random>
On Tue, Jun 10, 2008 at 12:33:49AM +0200, Andrea Arcangeli wrote:
> On Sun, Jun 08, 2008 at 11:35:49PM -0300, Marcelo Tosatti wrote:
> >
> > kvm_mmu_pte_write() does not handle 32-bit non-PAE large page backed
> > guests properly. It will instantiate two 2MB sptes pointing to the same
> > physical 2MB page when a guest large pte update is trapped.
> >
> > Instead of duplicating code to handle this, disallow directory level
> > updates to happen through kvm_mmu_pte_write(), so the two 2MB sptes
> > emulating one guest 4MB pte can be correctly created by the page fault
> > handling path.
>
> This fix reminded me of this stack trace I looked some time ago, it
> was also related to a 4M user pte IIRC, may they be related? In such a
> case we can should update the bug status.
>
> http://sourceforge.net/tracker/index.php?func=detail&aid=1929279&group_id=180599&atid=893831
>
> 7916:Mar 30 11:18:59 hmf kernel: RIP: 0010:[<ffffffff8882c99d>] [<ffffffff8882c99d>] :kvm:rmap_remove+0x12d/0x1e0
> 7932:Mar 30 11:18:59 hmf kernel: Call Trace:
> 7933:Mar 30 11:18:59 hmf kernel: [<ffffffff8882e870>] :kvm:kvm_mmu_pte_write+0x220/0x850
Don't think it is related, the bug which patch fixes can only be
triggered if the guest is large page backed, which does not seem to be
the case of this bug report.
7909:Mar 30 11:18:59 hmf kernel: rmap_remove: ffff810005fb2000 2f7b5063 0->BUG
This seems to be a regular 4k shadow pte:
0x63 = PT_PRESENT|PT_WRITABLE|PT_ACCESSED|PT_DIRTY
Its tainted too: nvidia(P)
prev parent reply other threads:[~2008-06-10 16:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-09 2:35 KVM: MMU: large page update_pte issue with non-PAE 32-bit guests Marcelo Tosatti
2008-06-09 22:33 ` Andrea Arcangeli
2008-06-10 16:44 ` Marcelo Tosatti [this message]
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=20080610164450.GA4316@dmt.cnet \
--to=mtosatti@redhat.com \
--cc=andrea@qumranet.com \
--cc=avi@qumranet.com \
--cc=kvm@vger.kernel.org \
/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