From: Vasant Hegde vasant.hegde@amd.com
[ Upstream commit 2cc73c5712f97de98c38c2fafc1f288354a9f3c3 ]
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@linux.intel.com Reported-by: Matt Fagnani matt.fagnani@bell.net Signed-off-by: Vasant Hegde vasant.hegde@amd.com Reviewed-by: Jason Gunthorpe jgg@nvidia.com Tested-by: Matt Fagnani matt.fagnani@bell.net Link: https://lore.kernel.org/r/20230215052642.6016-1-vasant.hegde@amd.com Link: https://bugzilla.kernel.org/show_bug.cgi?id=216865 Link: https://lore.kernel.org/lkml/15d0f9ff-2a56-b3e9-5b45-e6b23300ae3b@leemhuis.i... Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/iommu.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 959d895fc1dff..f9eb1a4bb5bb0 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2085,8 +2085,22 @@ static int __iommu_attach_group(struct iommu_domain *domain,
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; }