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From: Gleb Natapov <gleb@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: "Jan Kiszka" <jan.kiszka@web.de>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	lkml <linux-kernel@vger.kernel.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Steven Rostedt" <rostedt@goodmis.org>, x86-ml <x86@kernel.org>,
	kvm@vger.kernel.org, "Jörg Rödel" <joro@8bytes.org>
Subject: Re: __schedule #DF splat
Date: Sun, 29 Jun 2014 17:27:22 +0300	[thread overview]
Message-ID: <20140629142722.GH18167@minantech.com> (raw)
In-Reply-To: <20140629140104.GB12528@pd.tnic>

On Sun, Jun 29, 2014 at 04:01:04PM +0200, Borislav Petkov wrote:
> On Sun, Jun 29, 2014 at 04:42:47PM +0300, Gleb Natapov wrote:
> > Please do so and let us know.
> 
> Yep, just did. Reverting ae9fedc793 fixes the issue.
> 
> > reinj:1 means that previous injection failed due to another #PF that
> > happened during the event injection itself This may happen if GDT or fist
> > instruction of a fault handler is not mapped by shadow pages, but here
> > it says that the new page fault is at the same address as the previous
> > one as if GDT is or #PF handler is mapped there. Strange. Especially
> > since #DF is injected successfully, so GDT should be fine. May be wrong
> > cpl makes svm crazy?
> 
> Well, I'm not going to even pretend to know kvm to know *when* we're
> saving VMCB state but if we're saving the wrong CPL and then doing the
> pagetable walk, I can very well imagine if the walker gets confused. One
> possible issue could be U/S bit (bit 2) in the PTE bits which allows
> access to supervisor pages only when CPL < 3. I.e., CPL has effect on
> pagetable walk and a wrong CPL level could break it.
> 
> All a conjecture though...
> 
Looks plausible, still strange that second #PF is at the same address as the first one though.
Anyway, not we have the commit to blame.

--
			Gleb.

  reply	other threads:[~2014-06-29 14:27 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-25 15:32 __schedule #DF splat Borislav Petkov
2014-06-25 20:26 ` Borislav Petkov
2014-06-27 10:18   ` Borislav Petkov
2014-06-27 11:41     ` Paolo Bonzini
2014-06-27 11:55       ` Borislav Petkov
2014-06-27 12:01         ` Paolo Bonzini
2014-06-27 12:10           ` Borislav Petkov
2014-06-28 11:44             ` Borislav Petkov
2014-06-29  6:46               ` Gleb Natapov
2014-06-29  9:56                 ` Jan Kiszka
2014-06-29 10:24                   ` Gleb Natapov
2014-06-29 10:31                     ` Jan Kiszka
2014-06-29 10:53                       ` Gleb Natapov
2014-06-29 10:59                         ` Jan Kiszka
2014-06-29 11:51                           ` Borislav Petkov
2014-06-29 12:22                             ` Jan Kiszka
2014-06-29 13:14                               ` Borislav Petkov
2014-06-29 13:42                                 ` Gleb Natapov
2014-06-29 14:01                                   ` Borislav Petkov
2014-06-29 14:27                                     ` Gleb Natapov [this message]
2014-06-29 14:32                                       ` Jan Kiszka
2014-06-29 14:51                                         ` Jan Kiszka
2014-06-29 15:12                                           ` [PATCH] KVM: SVM: Fix CPL export via SS.DPL Jan Kiszka
2014-06-29 18:00                                             ` Borislav Petkov
2014-06-30 15:01                                             ` Paolo Bonzini
2014-06-30 15:03                                               ` Jan Kiszka
2014-06-30 15:15                                                 ` Borislav Petkov
2014-06-30 15:25                                                   ` Gleb Natapov
2014-06-30 15:26                                                 ` Paolo Bonzini
2014-06-29 13:46                                 ` __schedule #DF splat Borislav Petkov

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