Re: [PATCH 2/2] iommu/amd: Handle PPR log overflow

[Vasant Hegde <vasant.hegde@amd.com>]

Hi Jerry,

On 6/14/2023 1:59 AM, Jerry Snitselaar wrote:
> On Fri, Jun 09, 2023 at 10:17:46AM +0000, Vasant Hegde wrote:
>> Some ATS-capable peripherals can issue requests to the processor to service
>> peripheral page requests using PCIe PRI (the Page Request Interface). IOMMU
>> supports PRI using PPR log buffer. IOMMU writes PRI request to PPR log
>> buffer and sends PPR interrupt to host. When there is no space in the
>> PPR log buffer (PPR log overflow) it will set PprOverflow bit in 'MMIO
>> Offset 2020h IOMMU Status Register'. When this happens PPR log needs to be
>> restarted as specified in IOMMU spec [1] section 2.6.2.
>>
>> When handling the event it just resumes the PPR log without resizing
>> (similar to the way event and GA log overflow is handled).
>>
>> Failing to handle PPR overflow means device may not work properly as
>> IOMMU stops processing new PPR events from device.
>>
>> [1] https://www.amd.com/system/files/TechDocs/48882_3.07_PUB.pdf
>>
>> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
> 
> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

Thanks for the review.

> 
> Will the code re-org you are doing move the event log overflow check
> next to the event log processing check, like is done with the ga log
> and ppr log?

Yes. Its handled as part of IOMMU interrupt split series.

-Vasant