Messages in this thread | | | Date | Wed, 22 Jun 2022 22:27:08 +0800 | Subject | Re: [PATCH v2 1/1] iommu/vt-d: Fix RID2PASID setup failure | From | Baolu Lu <> |
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On 2022/6/22 17:09, Ethan Zhao wrote: > > 在 2022/6/22 12:41, Lu Baolu 写道: >> The IOMMU driver shares the pasid table for PCI alias devices. When the >> RID2PASID entry of the shared pasid table has been filled by the first >> device, the subsequent devices will encounter the "DMAR: Setup RID2PASID >> failed" failure as the pasid entry has already been marked as present. As >> the result, the IOMMU probing process will be aborted. >> >> This fixes it by skipping RID2PASID setting if the pasid entry has been >> populated. This works because the IOMMU core ensures that only the same >> IOMMU domain can be attached to all PCI alias devices at the same time. >> Therefore the subsequent devices just try to setup the RID2PASID entry >> with the same domain, which is negligible. This also adds domain validity >> checks for more confidence anyway. >> >> Fixes: ef848b7e5a6a0 ("iommu/vt-d: Setup pasid entry for RID2PASID >> support") >> Reported-by: Chenyi Qiang <chenyi.qiang@intel.com> >> Cc: stable@vger.kernel.org >> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> >> --- >> drivers/iommu/intel/pasid.c | 22 ++++++++++++++++------ >> 1 file changed, 16 insertions(+), 6 deletions(-) >> >> Change log: >> v2: >> - Add domain validity check in RID2PASID entry setup. >> >> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c >> index cb4c1d0cf25c..4f3525f3346f 100644 >> --- a/drivers/iommu/intel/pasid.c >> +++ b/drivers/iommu/intel/pasid.c >> @@ -575,6 +575,19 @@ static inline int pasid_enable_wpe(struct >> pasid_entry *pte) >> return 0; >> }; >> +/* >> + * Return true if @pasid is RID2PASID and the domain @did has already >> + * been setup to the @pte. Otherwise, return false. PCI alias devices >> + * probably share the single RID2PASID pasid entry in the shared pasid >> + * table. It's reasonable that those devices try to set a share domain >> + * in their probe paths. >> + */ > > I am thinking about the counter-part, the intel_pasid_tear_down_entry(), > > Multi devices share the same PASID entry, then one was detached from the > domain, > > so the entry doesn't exist anymore, while another devices don't know > about the change, > > and they are using the mapping, is it possible case ?shared thing, no > refer-counter, > > am I missing something ?
No. You are right. When any alias device is hot-removed from the system, the shared RID2PASID will be cleared without any notification to other devices. Hence any DMAs from those devices are blocked.
We still have a lot to do for sharing pasid table among alias devices. Before we arrive there, let's remove it for now.
Best regards, baolu
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