Re: [PATCH v3 3/7] iommu/vt-d: Always reserve a domain ID for identity setup

[Jason Gunthorpe]

On Tue, Aug 06, 2024 at 10:39:37AM +0800, Lu Baolu wrote:
> We will use a global static identity domain. Reserve a static domain ID
> for it.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/intel/iommu.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 723ea9f3f501..c019fb3b3e78 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1440,10 +1440,10 @@ static int iommu_init_domains(struct intel_iommu *iommu)
>  	 * entry for first-level or pass-through translation modes should
>  	 * be programmed with a domain id different from those used for
>  	 * second-level or nested translation. We reserve a domain id for
> -	 * this purpose.
> +	 * this purpose. This domain id is also used for identity domain
> +	 * in legacy mode.
>  	 */
> -	if (sm_supported(iommu))
> -		set_bit(FLPT_DEFAULT_DID, iommu->domain_ids);
> +	set_bit(FLPT_DEFAULT_DID, iommu->domain_ids);

That should probablyturn into an IDA someday, it would likely be more
memory efficient than bitmap_zalloc()

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason