Re: [PATCH v6 14/14] iommu/arm-smmu-v3: Set MEV bit in nested STE for DoS mitigations

On Tue, Feb 18, 2025 at 02:52:29PM -0400, Jason Gunthorpe wrote:

On Tue, Feb 18, 2025 at 06:17:15PM +0000, Pranjal Shrivastava wrote:

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Is MEV available only in nested mode? Otherwise it perhaps makes sense to turn it on in all configurations in IOMMUFD paths...

I think the arm-smmu-v3's iommufd implementation only supports nested which could be the reason.

I think starting with MEV in this limited case is reasonable.

I agree it makes sense to always turn it on from a production perspective..

Then, I will just add a line to the commit log: "In the future, we might want to enable the MEV for non-nested cases too such as domain->type == IOMMU_DOMAIN_UNMANAGED or even IOMMU_DOMAIN_DMA."

Thanks Nicolin