Messages in this thread | | | Date | Fri, 11 Jun 2021 11:45:24 +0100 | From | Will Deacon <> | Subject | Re: [PATCH 1/2] iommu: Fix race condition during default domain allocation |
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On Thu, Jun 10, 2021 at 09:46:53AM +0530, Ashish Mhetre wrote: > Domain is getting created more than once during asynchronous multiple > display heads(devices) probe. All the display heads share same SID and > are expected to be in same domain. As iommu_alloc_default_domain() call > is not protected, the group->default_domain and group->domain are ending > up with different domains and leading to subsequent IOMMU faults. > Fix this by protecting iommu_alloc_default_domain() call with group->mutex.
Can you provide some more information about exactly what the h/w configuration is, and the callstack which exhibits the race, please?
> Signed-off-by: Ashish Mhetre <amhetre@nvidia.com> > --- > drivers/iommu/iommu.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 808ab70..2700500 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -273,7 +273,9 @@ int iommu_probe_device(struct device *dev) > * support default domains, so the return value is not yet > * checked. > */ > + mutex_lock(&group->mutex); > iommu_alloc_default_domain(group, dev); > + mutex_unlock(&group->mutex);
It feels wrong to serialise this for everybody just to cater for systems with aliasing SIDs between devices.
Will
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