RE: [PATCH v3] iommu/vt-d: Fix PASID directory pointer coherency

[Tian, Kevin]

> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, April 21, 2023 10:34 AM
> 
> On 4/20/23 4:16 PM, Tian, Kevin wrote:
> >> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> >> Sent: Wednesday, April 5, 2023 11:45 PM
> >>
> >> On platforms that do not support IOMMU Extended capability bit 0
> >> Page-walk Coherency, CPU caches are not snooped when IOMMU is
> >> accessing
> >> any translation structures. IOMMU access goes only directly to
> >> memory. Intel IOMMU code was missing a flush for the PASID table
> >> directory that resulted in the unrecoverable fault as shown below.
> >>
> >> This patch adds clflush calls whenever allocating and updating
> >> a PASID table directory to ensure cache coherency.
> >>
> >> On the reverse direction, there's no need to clflush the PASID directory
> >> pointer when we deactivate a context entry in that IOMMU hardware will
> >> not see the old PASID directory pointer after we clear the context entry.
> >> PASID directory entries are also never freed once allocated.
> >>
> >> [    0.555386] DMAR: DRHD: handling fault status reg 3
> >> [    0.555805] DMAR: [DMA Read NO_PASID] Request device [00:0d.2] fault
> >> addr 0x1026a4000 [fault reason 0x51] SM: Present bit in Directory Entry is
> >> clear
> >> [    0.556348] DMAR: Dump dmar1 table entries for IOVA 0x1026a4000
> >> [    0.556348] DMAR: scalable mode root entry: hi 0x0000000102448001,
> low
> >> 0x0000000101b3e001
> >> [    0.556348] DMAR: context entry: hi 0x0000000000000000, low
> >> 0x0000000101b4d401
> >> [    0.556348] DMAR: pasid dir entry: 0x0000000101b4e001
> >> [    0.556348] DMAR: pasid table entry[0]: 0x0000000000000109
> >> [    0.556348] DMAR: pasid table entry[1]: 0x0000000000000001
> >> [    0.556348] DMAR: pasid table entry[2]: 0x0000000000000000
> >> [    0.556348] DMAR: pasid table entry[3]: 0x0000000000000000
> >> [    0.556348] DMAR: pasid table entry[4]: 0x0000000000000000
> >> [    0.556348] DMAR: pasid table entry[5]: 0x0000000000000000
> >> [    0.556348] DMAR: pasid table entry[6]: 0x0000000000000000
> >> [    0.556348] DMAR: pasid table entry[7]: 0x0000000000000000
> >> [    0.556348] DMAR: PTE not present at level 4
> >>
> >> Cc: <stable@xxxxxxxxxxxxxxx>
> >> Fixes: 0bbeb01a4faf ("iommu/vt-d: Manage scalalble mode PASID tables")
> >> Reported-by: Sukumar Ghorai <sukumar.ghorai@xxxxxxxxx>
> >> Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
> >> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> >> ---
> >> v3: Add clflush after PASID directory allocation to prevent malicious
> >> device attack with unauthorized PASIDs. Also flush all the PASID entries
> >> after directory updates. (Baolu)
> >> v2: Add clflush to PASID directory update case (Baolu, Kevin review)
> >> ---
> >>   drivers/iommu/intel/iommu.c | 2 ++
> >>   drivers/iommu/intel/pasid.c | 7 +++++++
> >>   2 files changed, 9 insertions(+)
> >>
> >> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> >> index 59df7e42fd53..161342e7149d 100644
> >> --- a/drivers/iommu/intel/iommu.c
> >> +++ b/drivers/iommu/intel/iommu.c
> >> @@ -1976,6 +1976,8 @@ static int domain_context_mapping_one(struct
> >> dmar_domain *domain,
> >>   		pds = context_get_sm_pds(table);
> >>   		context->lo = (u64)virt_to_phys(table->table) |
> >>   				context_pdts(pds);
> >> +		if (!ecap_coherent(iommu->ecap))
> >> +			clflush_cache_range(table->table, sizeof(u64));
> >
> > v2 of this patch was already merged w/o this change.
> 
> The merged patch is v4.
> 
> https://lore.kernel.org/all/20230209212843.1788125-1-
> jacob.jun.pan@xxxxxxxxxxxxxxx/
> 
> > can you elaborate the purpose of v3? Here no flush is required as long
> > as it's done in other two places below.
> 
> No above code in the merged patch.
> 

so this one might be just sent inadvertently by Jacob.