[bug report] iommu_dma_unmap_sg() is very slow then running IO from remote numa node

[John Garry]

On 22/07/2021 13:53, Marc Zyngier wrote:
> Hi John,
> 
> [...]
> 
>>     Your kernel log should show:
>>     [    0.000000] GICv3: Pseudo-NMIs enabled using forced ICC_PMR_EL1
>> synchronisation
> 
> Unrelated, but you seem to be running with ICC_CTLR_EL3.PMHE set,
> which makes the overhead of pseudo-NMIs much higher than it should be
> (you take a DSB SY on each interrupt unmasking).
> 
> If you are not using 1:N distribution of SPIs on the secure side,
> consider turning that off in your firmware. This should make NMIs
> slightly more pleasant to use.

Thanks for the hint. I speak to the BIOS guys.

John