Re: [Xen-devel] [PATCH] xen/x86: vpmu: Unmap per-vCPU PMU page when the domain is destroyed

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.11.2019 11:57,  Durrant, Paul  wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 27 November 2019 09:44
>> To: Durrant, Paul <pdurrant@xxxxxxxxxx>; Grall, Julien <jgrall@xxxxxxxxxx>
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Andrew Cooper
>> <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>; Wei
>> Liu <wl@xxxxxxx>
>> Subject: Re: [PATCH] xen/x86: vpmu: Unmap per-vCPU PMU page when the
>> domain is destroyed
>>
>> On 26.11.2019 18:17, Paul Durrant wrote:
>>> From: Julien Grall <jgrall@xxxxxxxxxx>
>>>
>>> A guest will setup a shared page with the hypervisor for each vCPU via
>>> XENPMU_init. The page will then get mapped in the hypervisor and only
>>> released when XEMPMU_finish is called.
>>>
>>> This means that if the guest is not shutdown gracefully (such as via xl
>>> destroy), the page will stay mapped in the hypervisor.
>>
>> Isn't this still too weak a description? It's not the tool stack
>> invoking XENPMU_finish, but the guest itself afaics. I.e. a
>> misbehaving guest could prevent proper cleanup even with graceful
>> shutdown.
>>
> 
> Ok, how about 'if the guest fails to invoke XENPMU_finish, e.g. if
> it is destroyed, rather than cleanly shut down'?

Sounds good.

Jan

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