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Re: [Xen-devel] [PATCH 20 of 20] n2 MSR handling and capability exposure

To: Jeroen Groenewegen van der Weyden <groen692@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 20 of 20] n2 MSR handling and capability exposure
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Tue, 26 Jul 2011 12:42:33 +0100
Cc: "Christoph.Egger@xxxxxxx" <Christoph.Egger@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Dong, Eddie" <eddie.dong@xxxxxxxxx>
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At 12:46 +0200 on 26 Jul (1311684389), Jeroen Groenewegen van der Weyden wrote:
> Here my input

Thanks.  Looks very similar to the bug I thought I fixed with my patch.

VCPUs 1 and 3 are always at 0xa01a1c9d: <0f> 01 c2 eb 03 0f 01 c3
which is probably this fragment of code from KVM's vmx_vcpu_run():

        /* Enter guest mode */
        "jne .Llaunched \n\t"
        __ex(ASM_VMX_VMLAUNCH) "\n\t"
        "jmp .Lkvm_vmx_return \n\t"
        ".Llaunched: " __ex(ASM_VMX_VMRESUME) "\n\t"
        ".Lkvm_vmx_return: "

So, just like the case I saw, they're trying to VMLAUNCH a VMCS and
failing.  That should only fail if the VMCS is already launched. 

I think the reason they're _stuck_ is that error paths for VMLAUNCH and
VMRESUME emulation are wrong; I can fix them up a little but I suspect
that won't solve the problem; just change it from a hang to some other
failure mode.

Can you try the attached patch instead of the previous one? 


Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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