Re: [PATCH 1/3] iommu/vt-d: Use ida to manage domain id

[Baolu Lu]

On 4/24/2025 3:37 PM, Tian, Kevin wrote:
> > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > Sent: Wednesday, April 23, 2025 11:10 AM
> >
> >   static void free_dmar_iommu(struct intel_iommu *iommu)
> >   {
> > -	if (iommu->domain_ids) {
> > -		bitmap_free(iommu->domain_ids);
> > -		iommu->domain_ids = NULL;
> > -	}
> > +	ida_destroy(&iommu->domain_ida);
>
> since ida_init() is in alloc_iommu() now, the destroy can be
> moved to free_iommu().

Sure.

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index e25e8d3dedcb..9e17e8e56308 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1198,6 +1198,7 @@ static void free_iommu(struct intel_iommu *iommu)
        if (iommu->reg)
                unmap_iommu(iommu);

+       ida_destroy(&iommu->domain_ida);
        ida_free(&dmar_seq_ids, iommu->seq_id);
        kfree(iommu);
 }
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index f784df122d7a..0002511c561f 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1304,8 +1304,6 @@ static void disable_dmar_iommu(struct intel_iommu 
*iommu)

 static void free_dmar_iommu(struct intel_iommu *iommu)
 {
-       ida_destroy(&iommu->domain_ida);
-
        if (iommu->copied_tables) {
                bitmap_free(iommu->copied_tables);
                iommu->copied_tables = NULL;

> > @@ -1399,14 +1356,13 @@ int domain_attach_iommu(struct dmar_domain
> > *domain, struct intel_iommu *iommu)
> >   		return 0;
> >   	}
> >
> > -	ndomains = cap_ndoms(iommu->cap);
> > -	num = find_first_zero_bit(iommu->domain_ids, ndomains);
> > -	if (num >= ndomains) {
> > +	num = ida_alloc_range(&iommu->domain_ida, FLPT_DEFAULT_DID +
> > 1,
> > +			      cap_ndoms(iommu->cap) - 1, GFP_ATOMIC);
>
> let's define a macro e.g. FIRST_DID for min.

Okay, how about IDA_START_DID?

Thanks,
baolu

> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>