Re: [PATCH v3 1/1] iommu/vt-d: Remove caching mode check before device TLB flush

[Baolu Lu]

On 4/15/24 9:38 AM, Lu Baolu wrote:
> The Caching Mode (CM) of the Intel IOMMU indicates if the hardware
> implementation caches not-present or erroneous translation-structure
> entries except for the first-stage translation. The caching mode is
> irrelevant to the device TLB, therefore there is no need to check it
> before a device TLB invalidation operation.
>
> Remove two caching mode checks before device TLB invalidation in the
> driver. The removal of these checks doesn't change the driver's behavior
> in critical map/unmap paths. Hence, there is no functionality or
> performance impact, especially since commit <29b32839725f> ("iommu/vt-d:
> Do not use flush-queue when caching-mode is on") has already disabled
> flush-queue for caching mode. Therefore, caching mode will never call
> intel_flush_iotlb_all().
>
> Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> Reviewed-by: Kevin Tian<kevin.tian@xxxxxxxxx>
> ---
>   drivers/iommu/intel/iommu.c | 9 ++-------
>   1 file changed, 2 insertions(+), 7 deletions(-)

Patch has been queued for iommu/vt-d.

Best regards,
baolu