linux-kernel - Re: [PATCH 2/3] KVM: SVM: Restore correct registers after sel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100902162934.GD1964@amd.com>
Date:	Thu, 2 Sep 2010 18:29:34 +0200
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>
Subject: Re: [PATCH 2/3] KVM: SVM: Restore correct registers after sel_cr0
 intercept emulation

On Thu, Sep 02, 2010 at 12:02:02PM -0400, Avi Kivity wrote:
>   On 09/02/2010 06:29 PM, Joerg Roedel wrote:
> > This patch implements restoring of the correct rip, rsp, and
> > rax after the svm emulation in KVM injected a selective_cr0
> > write intercept into the guest hypervisor. The problem was
> > that the vmexit is emulated in the instruction emulation
> > which later commits the registers right after the write-cr0
> > instruction. So the l1 guest will continue to run with the
> > l2 rip, rsp and rax resulting in unpredictable behavior.
> 
> Please post a unit test for this.

Will do. Should be an easy test.

> > This patch is not the final word, it is just an easy patch
> > to fix the issue. The real fix will be done when the
> > instruction emulator is made aware of nested virtualization.
> > Until this is done this patch fixes the issue and provides
> > an easy way to fix this in -stable too.
> 
> I agree.  We can probably use X86EMUL_PROPAGATE_FAULT to abort 
> emulation, but looking at the code, it will take some refactoring.

I thought of an X86EMUL_INTERCEPTED. An architecture specific function
is called after instruction decoding which checks if an intercept is
necessary. If it returns X86EMUL_INTERCEPTED then the instruction
emulation is discarded and kvm goes straight back into the guest.


	Joerg

-- 
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/