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

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Message-ID: <4541dba3-1a4b-45f6-a607-fe2fe9a9f014@linux.intel.com>
Date: Thu, 24 Apr 2025 17:01:35 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Jason Gunthorpe <jgg@...pe.ca>
Cc: baolu.lu@...ux.intel.com, "iommu@...ts.linux.dev"
 <iommu@...ts.linux.dev>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] iommu/vt-d: Use ida to manage domain id

On 4/24/2025 3:37 PM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> 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@...el.com>