This is a note to let you know that I've just added the patch titled iommu: Attach device group to old domain in error path to the 6.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: iommu-attach-device-group-to-old-domain-in-error-path.patch and it can be found in the queue-6.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 2cc73c5712f97de98c38c2fafc1f288354a9f3c3 Mon Sep 17 00:00:00 2001 From: Vasant Hegde <vasant.hegde@xxxxxxx> Date: Wed, 15 Feb 2023 05:26:40 +0000 Subject: iommu: Attach device group to old domain in error path From: Vasant Hegde <vasant.hegde@xxxxxxx> commit 2cc73c5712f97de98c38c2fafc1f288354a9f3c3 upstream. iommu_attach_group() attaches all devices in a group to domain and then sets group domain (group->domain). Current code (__iommu_attach_group()) does not handle error path. This creates problem as devices to domain attachment is in inconsistent state. Flow: - During boot iommu attach devices to default domain - Later some device driver (like amd/iommu_v2 or vfio) tries to attach device to new domain. - In iommu_attach_group() path we detach device from current domain. Then it tries to attach devices to new domain. - If it fails to attach device to new domain then device to domain link is broken. - iommu_attach_group() returns error. - At this stage iommu_attach_group() caller thinks, attaching device to new domain failed and devices are still attached to old domain. - But in reality device to old domain link is broken. It will result in all sort of failures (like IO page fault) later. To recover from this situation, we need to attach all devices back to the old domain. Also log warning if it fails attach device back to old domain. Suggested-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> Reported-by: Matt Fagnani <matt.fagnani@xxxxxxxx> Signed-off-by: Vasant Hegde <vasant.hegde@xxxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Tested-by: Matt Fagnani <matt.fagnani@xxxxxxxx> Link: https://lore.kernel.org/r/20230215052642.6016-1-vasant.hegde@xxxxxxx Link: https://bugzilla.kernel.org/show_bug.cgi?id=216865 Link: https://lore.kernel.org/lkml/15d0f9ff-2a56-b3e9-5b45-e6b23300ae3b@xxxxxxxxxxxxx/ Signed-off-by: Joerg Roedel <jroedel@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/iommu/iommu.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2124,8 +2124,22 @@ static int __iommu_attach_group(struct i ret = __iommu_group_for_each_dev(group, domain, iommu_group_do_attach_device); - if (ret == 0) + if (ret == 0) { group->domain = domain; + } else { + /* + * To recover from the case when certain device within the + * group fails to attach to the new domain, we need force + * attaching all devices back to the old domain. The old + * domain is compatible for all devices in the group, + * hence the iommu driver should always return success. + */ + struct iommu_domain *old_domain = group->domain; + + group->domain = NULL; + WARN(__iommu_group_set_domain(group, old_domain), + "iommu driver failed to attach a compatible domain"); + } return ret; } Patches currently in stable-queue which might be from vasant.hegde@xxxxxxx are queue-6.2/iommu-attach-device-group-to-old-domain-in-error-path.patch queue-6.2/iommu-amd-improve-page-fault-error-reporting.patch queue-6.2/iommu-amd-fix-error-handling-for-pdev_pri_ats_enable.patch queue-6.2/iommu-amd-skip-attach-device-domain-is-same-as-new-domain.patch