Re: [PATCH v7 12/24] iommu/arm-smmu-v3: Add support for VHE

Will Deacon
2020-05-21T14:17:03Z

On Tue, May 19, 2020 at 07:54:50PM +0200, Jean-Philippe Brucker wrote:
> ARMv8.1 extensions added Virtualization Host Extensions (VHE), which allow
> to run a host kernel at EL2. When using normal DMA, Device and CPU address
> spaces are dissociated, and do not need to implement the same
> capabilities, so VHE hasn't been used in the SMMU until now.
>
> With shared address spaces however, ASIDs are shared between MMU and SMMU,
> and broadcast TLB invalidations issued by a CPU are taken into account by
> the SMMU. TLB entries on both sides need to have identical exception level
> in order to be cleared with a single invalidation.
>
> When the CPU is using VHE, enable VHE in the SMMU for all STEs. Normal DMA
> mappings will need to use TLBI_EL2 commands instead of TLBI_NH, but
> shouldn't be otherwise affected by this change.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> drivers/iommu/arm-smmu-v3.c | 31 ++++++++++++++++++++++++++-----
> 1 file changed, 26 insertions(+), 5 deletions(-)

Acked-by: Will Deacon <will@kernel.org>

Will