On 2022/8/18 16:32, Tian, Kevin wrote:
From: Lu Baolu baolu.lu@linux.intel.com Sent: Wednesday, August 17, 2022 9:11 AM
The translation table copying code for kdump kernels is currently based on the extended root/context entry formats of ECS mode defined in older VT-d v2.5, and doesn't handle the scalable mode formats. This causes the kexec capture kernel boot failure with DMAR faults if the IOMMU was enabled in scalable mode by the previous kernel.
The ECS mode has already been deprecated by the VT-d spec since v3.0 and Intel IOMMU driver doesn't support this mode as there's no real hardware implementation. Hence this converts ECS checking in copying table code into scalable mode.
The existing copying code consumes a bit in the context entry as a mark of copied entry. This marker needs to work for the old format as well as for extended context entries. It's hard to find such a bit for both
The 2nd sentence "This marker..." is misleading. better removed.
Okay. I will make it like "It needs to work for ...".
legacy and scalable mode context entries. This replaces it with a per- IOMMU bitmap.
Fixes: 7373a8cc38197 ("iommu/vt-d: Setup context and enable RID2PASID support") Cc: stable@vger.kernel.org Reported-by: Jerry Snitselaar jsnitsel@redhat.com Tested-by: Wen Jin wen.jin@intel.com Signed-off-by: Lu Baolu baolu.lu@linux.intel.com
...
@@ -2735,8 +2693,8 @@ static int copy_translation_tables(struct intel_iommu *iommu) bool new_ext, ext;
rtaddr_reg = dmar_readq(iommu->reg + DMAR_RTADDR_REG);
- ext = !!(rtaddr_reg & DMA_RTADDR_RTT);
- new_ext = !!ecap_ecs(iommu->ecap);
- ext = !!(rtaddr_reg & DMA_RTADDR_SMT);
- new_ext = !!ecap_smts(iommu->ecap);
should be !!sm_supported()
Not really. The IOMMU was setup by the previous kernel. Here we just check whether the scalable mode was enabled there.
/* * The RTT bit can only be changed when translation is disabled, @@ -2747,6 +2705,10 @@ static int copy_translation_tables(struct intel_iommu *iommu) if (new_ext != ext) return -EINVAL;
- iommu->copied_tables = bitmap_zalloc(BIT_ULL(16), GFP_KERNEL);
- if (!iommu->copied_tables)
return -ENOMEM;- old_rt_phys = rtaddr_reg & VTD_PAGE_MASK; if (!old_rt_phys) return -EINVAL;
Out of curiosity. What is the rationale that we copy root table and context tables but not pasid tables?
We only copy the context table and reconstruct it when the default domain is attached. Before that, there's no need to reconstruct the pasid table, hence it's safe to use the previous pasid tables.
Best regards, baolu