From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@qumranet.com>
Subject: Re: Oops for sale
Date: Mon, 09 Jun 2008 19:33:19 +0300
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References: <48494341.1060007@redhat.com> <4849A2B7.1030305@qumranet.com> <484D3310.6070908@redhat.com>
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To: Gerd Hoffmann <kraxel@redhat.com>
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Gerd Hoffmann wrote:
> Log attached.  Scanning it and having a brief look at the source code
> makes me suspect it could be a flags update triggering this: Due to
> 64bit xen guest kernels running in ring3 xenner may just flip the user
> bit (off->on) in the page table handler, which is a unusual operation I
> guess ...
>   

The unshadow-on-userspace-access heuristic is broken.  Since it is also 
bad for Xenner, try removing the following lines:

        spte |= PT_WRITABLE_MASK;
        if (user_fault) {
            mmu_unshadow(vcpu->kvm, gfn);
            goto unshadowed;
        }


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.