Re: [bug report] iommu/arm-smmu-v3: Refactor write_ctx_desc

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Feb 02, 2024 at 09:33:14PM +0900, Michael Shavit wrote:
> Jason, should we consider moving arm_smmu_get_cd_ptr() further up the
> call-stack as a standalone patch to remediate this report in the
> shorter term? It won't make this static checker happy, but should at
> least resolve any true positives.

Moving is the right answer, but I suspect it is too hard for rc. Lets
leave it to my series that already exists.

Instead we can preallocate:

--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -588,6 +588,11 @@ static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
 {
        int ret = 0;
        struct mm_struct *mm = domain->mm;
+       struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+
+       /* Preallocate the required leafs outside locks */
+       if (!arm_smmu_get_cd_ptr(master, id))
+               return -ENOMEM;
 
        mutex_lock(&sva_lock);
        ret = __arm_smmu_sva_bind(dev, mm);

It won't silence Dan's warning warning but it will correct the bug for
now.

I'll send a patch

Jason