linux-kernel - Re: [PATCH v1 2/6] iommu/vt-d: Use IDA interface to manage iommu sequence id

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Date:   Fri, 1 Jul 2022 09:17:33 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>, Steve Wahl <steve.wahl@....com>
Cc:     baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Mike Travis <mike.travis@....com>,
        Dimitri Sivanich <sivanich@....com>,
        "Anderson, Russ" <russ.anderson@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/6] iommu/vt-d: Use IDA interface to manage iommu
 sequence id

On 6/30/22 4:21 PM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Saturday, June 25, 2022 8:52 PM
>>
>> @@ -1062,11 +1040,14 @@ static int alloc_iommu(struct dmar_drhd_unit
>> *drhd)
>>   	if (!iommu)
>>   		return -ENOMEM;
>>
>> -	if (dmar_alloc_seq_id(iommu) < 0) {
>> +	iommu->seq_id = ida_alloc_range(&dmar_seq_ids, 0,
>> +					DMAR_UNITS_SUPPORTED,
> 
> should be "DMAR_UNITS_SUPPORTED - 1"

Yes, according to "@max: Highest ID to allocate.". Updated.

>> GFP_KERNEL);
>> +	if (iommu->seq_id < 0) {
>>   		pr_err("Failed to allocate seq_id\n");
>>   		err = -ENOSPC;
>>   		goto error;
>>   	}
> 
> ida_alloc_range() returns error code already. No need to change it.
> 

Agreed. Updated as below:

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index bf43889b9d2a..6327b34f5aa7 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1041,10 +1041,10 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
                 return -ENOMEM;

         iommu->seq_id = ida_alloc_range(&dmar_seq_ids, 0,
-                                       DMAR_UNITS_SUPPORTED, GFP_KERNEL);
+                                       DMAR_UNITS_SUPPORTED - 1, 
GFP_KERNEL);
         if (iommu->seq_id < 0) {
                 pr_err("Failed to allocate seq_id\n");
-               err = -ENOSPC;
+               err = iommu->seq_id;
                 goto error;
         }
         sprintf(iommu->name, "dmar%d", iommu->seq_id);

Best regards,
baolu