Re: [Xen-devel] Xen 4.6.1 crash with altp2m enabledbydefault

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/08/16 11:01, Kevin.Mayer@xxxxxxxx wrote:
> Hi
>
> I took another look at Xen and a new crashdump.
> The last successful __vmwrite should be in 
> static void vmx_vcpu_update_vmfunc_ve(struct vcpu *v)
> [...]
>     __vmwrite(SECONDARY_VM_EXEC_CONTROL,
>               v->arch.hvm_vmx.secondary_exec_control);
> [...]
> After this the altp2m_vcpu_destroy wakes up the vcpu and is then finished.
>
> In nestedhvm_vcpu_destroy (nvmx_vcpu_destroy) the vmcs can overwritten (but 
> is not reached in our case as far as I can see):
>     if ( nvcpu->nv_n1vmcx )
>         v->arch.hvm_vmx.vmcs = nvcpu->nv_n1vmcx;
>
> In conclusion:
> When destroying a domain the altp2m_vcpu_destroy(v); path seems to mess up 
> the vmcs which ( only ) sometimes leads to a failed __vmwrite in 
> vmx_fpu_leave.
> That is as far as I can get with my understanding of the Xen code.
>
> Do you guys have any additional ideas what I could test / analyse?

Do you have easy reproduction instructions you could share?  Sadly, this
is looking like an issue which isn't viable to debug over email.

~Andrew

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