Re: [PATCH v3 2/7] iommu/vt-d: Remove identity mappings from si_domain

Jason Gunthorpe
2024-08-06T17:05:31Z

On Tue, Aug 06, 2024 at 10:39:36AM +0800, Lu Baolu wrote:
> As the driver has enforced DMA domains for devices managed by an IOMMU
> hardware that doesn't support passthrough translation mode, there is no
> need for static identity mappings in the si_domain. Remove the identity
> mapping code to avoid dead code.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel/iommu.c | 122 ++----------------------------------
> 1 file changed, 4 insertions(+), 118 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

I always wondered why this was so fine grained, I would have expected
it to work on blocks of 512 x 1G, once you allocate a memory for the
1G table level you may as well fill it with identity IOPTEs. The only
optimization point is how many blocks of 512x1G are needed..

Jason