Re: [PATCH 5.10 392/530] iommu/vt-d: Preset Access/Dirty bits for IOVA over FL

[Lu Baolu]

Hi Wolfgang,

On 5/15/21 9:28 PM, Wolfgang Müller wrote:
> Hi!
>
> First of all, apologies if this is the wrong place to post a problem
> report. I figured since I was going to reference a particular commit
> anyway I might as well reply to the patch series that (seemed to have)
> introduced the problem.
>
> > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> >
> > [ Upstream commit a8ce9ebbecdfda3322bbcece6b3b25888217f8e3 ]
> >
> > The Access/Dirty bits in the first level page table entry will be set
> > whenever a page table entry was used for address translation or write
> > permission was successfully translated. This is always true when using
> > the first-level page table for kernel IOVA. Instead of wasting hardware
> > cycles to update the certain bits, it's better to set them up at the
> > beginning.
>
> This commit seems to trigger a kernel panic very early in boot for me in
> 5.10.37 (36 is fine):

It seems due to the back-ported patch:

-	if (!sg) {
-		sg_res = nr_pages;
-		pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
+		if (domain->domain.type == IOMMU_DOMAIN_DMA) {
+			attr |= DMA_FL_PTE_ACCESS;
+			if (prot & DMA_PTE_WRITE)
+				attr |= DMA_FL_PTE_DIRTY;
+		}
 	}

+	pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;

Greg, do you want me to rework this patch, or submit an incremental fix?

Best regards,
baolu