Messages in this thread Patch in this message | | | Subject | Re: [PATCH] iommu/vt-d: Do not dump pasid table entries in kdump kernel | From | Lu Baolu <> | Date | Thu, 20 Jan 2022 10:58:48 +0800 |
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On 1/19/22 5:07 PM, Zelin Deng wrote: > In kdump kernel PASID translations won't be copied from previous kernel > even if scalable-mode is enabled, so pages of PASID translations are
Yes. The copy table support for scalable mode is still in my task list.
> non-present in kdump kernel. Attempt to access those address will cause > PF fault: > > [ 13.396476] DMAR: DRHD: handling fault status reg 3 > [ 13.396478] DMAR: [DMA Read NO_PASID] Request device [81:00.0] fault addr 0xffffd000 [fault reason 0x59] SM: Present bit in PA$ > [ 13.396480] DMAR: Dump dmar5 table entries for IOVA 0xffffd000 > [ 13.396481] DMAR: scalable mode root entry: hi 0x0000000000000000, low 0x00000000460d1001 > [ 13.396482] DMAR: context entry: hi 0x0000000000000008, low 0x00000010c4237401 > [ 13.396485] BUG: unable to handle page fault for address: ff110010c4237000 > [ 13.396486] #PF: supervisor read access in kernel mode > [ 13.396487] #PF: error_code(0x0000) - not-present page > [ 13.396488] PGD 5d201067 P4D 5d202067 PUD 0 > [ 13.396490] Oops: 0000 [#1] PREEMPT SMP NOPTI > [ 13.396491] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.16.0-rc6-next-20211224+ #6 > [ 13.396493] Hardware name: Intel Corporation EAGLESTREAM/EAGLESTREAM, BIOS EGSDCRB1.86B.0067.D12.2110190950 10/19/2021 > [ 13.396494] RIP: 0010:dmar_fault_dump_ptes+0x13b/0x295 > > Hence skip dumping pasid table entries if in kdump kernel.
This just asks dmar_fault_dump_ptes() to keep silent. The problem is that the context entry is mis-configured. Perhaps we should disable copy table for scalable mode for now. How about below change?
--- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -3337,10 +3337,11 @@ static int __init init_dmars(void)
init_translation_status(iommu);
- if (translation_pre_enabled(iommu) && !is_kdump_kernel()) { + if (translation_pre_enabled(iommu) && + (!is_kdump_kernel() || sm_supported(iommu))) { iommu_disable_translation(iommu); clear_translation_pre_enabled(iommu); - pr_warn("Translation was enabled for %s but we are not in kdump mode\n", + pr_warn("Translation was enabled for %s but we are not in kdump mode or copy table not supported\n", iommu->name); }
> Fixes: 914ff7719e8a (“iommu/vt-d: Dump DMAR translation structure when DMA fault occurs”) > Signed-off-by: Zelin Deng <zelin.deng@linux.alibaba.com> > --- > drivers/iommu/intel/iommu.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > index 92fea3fb..f0134cf 100644 > --- a/drivers/iommu/intel/iommu.c > +++ b/drivers/iommu/intel/iommu.c > @@ -1074,6 +1074,12 @@ void dmar_fault_dump_ptes(struct intel_iommu *iommu, u16 source_id, > if (!sm_supported(iommu)) > goto pgtable_walk; > > + /* PASID translations is not copied, skip dumping pasid table entries > + * otherwise non-present page will be accessed. > + */ > + if (is_kdump_kernel()) > + goto pgtable_walk; > + > /* get the pointer to pasid directory entry */ > dir = phys_to_virt(ctx_entry->lo & VTD_PAGE_MASK); > if (!dir) { >
Best regards, baolu
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