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

[Matt Leinhos <matt@xxxxxxxxxx>]

Andrew,

Thank you for the tip. The crash does not happen when the "maxmem"
option in the config file is disabled. I still get funny behavior with
my driver, but I need to investigate that further.

Regards,
Matt

On 11/02/2016 08:23 AM, Andrew Cooper wrote:
> 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
> 

-- 
Matt Leinhos
Star Lab
https://starlab.io/

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