I'm sorry, I'm coming into this late and this is the first time I have reviewed this patch. I see that we are at v13, and I hate to come in with picky comments when a patch has already gone through 13 revisions... On Thu, Feb 22, 2024 at 04:02:51AM -0500, Ethan Zhao wrote: > Because surprise removal could happen anytime, e.g. user could request safe > removal to EP(endpoint device) via sysfs and brings its link down to do > surprise removal cocurrently. such aggressive cases would cause ATS > invalidation request issued to non-existence target device, then deadly > loop to retry that request after ITE fault triggered in interrupt context. > this patch aims to optimize the ITE handling by checking the target device > presence state to avoid retrying the timeout request blindly, thus avoid > hard lockup or system hang. > > Devices are valid ATS invalidation request target only when they reside "valid invalidation" is awkward wording. Can we instead say: Devices should only be invalidated when they are in the iommu->device_rbtree (probed, not released) and present. > in the iommu->device_rbtre (probed, not released) and present. ^ Missing e in _rbtree. > > Signed-off-by: Ethan Zhao <haifeng.zhao@xxxxxxxxxxxxxxx> This patch should have a Fixes tags and be backported to stable kernels. I think it goes back all the way... Fixes: 704126ad81b8 ("VT-d: handle Invalidation Queue Error to avoid system hang") > --- > drivers/iommu/intel/dmar.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c > index d14797aabb7a..d01d68205557 100644 > --- a/drivers/iommu/intel/dmar.c > +++ b/drivers/iommu/intel/dmar.c > @@ -1273,6 +1273,9 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index) > { > u32 fault; > int head, tail; > + u64 iqe_err, ite_sid; > + struct device *dev = NULL; > + struct pci_dev *pdev = NULL; > struct q_inval *qi = iommu->qi; > int shift = qi_shift(iommu); > > @@ -1317,6 +1320,13 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index) > tail = readl(iommu->reg + DMAR_IQT_REG); > tail = ((tail >> shift) - 1 + QI_LENGTH) % QI_LENGTH; > > + /* > + * SID field is valid only when the ITE field is Set in FSTS_REG > + * see Intel VT-d spec r4.1, section 11.4.9.9 > + */ > + iqe_err = dmar_readq(iommu->reg + DMAR_IQER_REG); > + ite_sid = DMAR_IQER_REG_ITESID(iqe_err); > + > writel(DMA_FSTS_ITE, iommu->reg + DMAR_FSTS_REG); > pr_info("Invalidation Time-out Error (ITE) cleared\n"); > > @@ -1326,6 +1336,21 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index) > head = (head - 2 + QI_LENGTH) % QI_LENGTH; > } while (head != tail); > > + /* > + * If got ITE, we need to check if the sid of ITE is one of the > + * current valid ATS invalidation target devices, if no, or the > + * target device isn't presnet, don't try this request anymore. > + * 0 value of ite_sid means old VT-d device, no ite_sid value. > + */ This comment is kind of confusing. /* * If we have an ITE, then we need to check whether the sid of the ITE * is in the rbtree (meaning it is probed and not released), and that * the PCI device is present. */ My comment is slightly shorter but I think it has the necessary information. > + if (ite_sid) { > + dev = device_rbtree_find(iommu, ite_sid); > + if (!dev || !dev_is_pci(dev)) > + return -ETIMEDOUT; -ETIMEDOUT is weird. The callers don't care which error code we return. Change this to -ENODEV or something > + pdev = to_pci_dev(dev); > + if (!pci_device_is_present(pdev) && > + ite_sid == pci_dev_id(pci_physfn(pdev))) The && confused me, but then I realized that probably "ite_sid == pci_dev_id(pci_physfn(pdev))" is always true. Can we delete that part? pdev = to_pci_dev(dev); if (!pci_device_is_present(pdev)) return -ENODEV; > + return -ETIMEDOUT; -ENODEV. > + } > if (qi->desc_status[wait_index] == QI_ABORT) > return -EAGAIN; > } Sorry, again for nit picking a v13 patch. I'm not a domain expert but this patchset seems reasonable to me. regards, dan carpenter