Re: [Xen-devel] [BUG] altp2m from domU crashes the host

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/11/16 13:16, Matt Leinhos wrote:
> Hello,
>
> I am working on a Linux driver that exercises the altp2m interface from
> a guest VM. Unfortunately, something goes horribly wrong and I end up
> crashing the Xen host.
>
> dom0 is Ubuntu 16.04; the domU guest is running Centos with Linux kernel
> 3.10.0-327.
>
> Following these steps on a domU guest that's running on Xen 4.8.0-rc4
> causes the attached crash.
>
> 1. Set a dummy handler for #VE in the guest IDT.
> 2. Enable altp2m (HVMOP_altp2m_set_domain_state)
> 3. Create a new altp2m view (HVMOP_altp2m_create_p2m)
> 4. Enable altp2m vcpu notification (HVMOP_altp2m_vcpu_enable_notify)
>
> The host crash happens immediately. I've also seen a delayed host crash
> with Xen 4.6, but I'm focusing on the 4.8 RC here.
>
> I don't know exactly which step causes the crash. I'll continue my
> investigation today.

You have configured PoD for your domain.  i.e. configured mem < maxmem.

PoD is compatible with just about everything, and is only useful for one
specific windows corner case.

xl/libxl should probably refuse to create a domain configured both with
PoD and altp2m.

~Andrew

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