[PATCH v2 12/12] x86/traps: Fix up invalid PASID

Andy Lutomirski luto at amacapital.net
Tue Jun 16 07:18:39 AEST 2020



> On Jun 15, 2020, at 1:56 PM, Luck, Tony <tony.luck at intel.com> wrote:
> 
> 
>> 
>> Are we planning to keep PASID live once a task has used it once or are we going to swap it lazily?  If the latter, a percpu variable might be better.
> 
> Current plan is "touch it once and the task owns it until exit(2)"
> 
> Maybe someday in the future when we have data on how applications
> actually use accelerators we could look at something more complex
> if usage patterns look like it would be beneficial.
> 
> 

So what’s the RDMSR for?  Surely you
have some state somewhere that says “this task has a PASID.”  Can’t you just make sure that stays in sync with the MSR?  Then, on #GP, if the task already has a PASID, you know the MSR is set.


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