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Message-ID: <f1b2e7fa-7be3-9e4b-1eba-5dba01b88c19@linux.intel.com>
Date: Tue, 27 Jun 2023 16:01:01 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>,
"Liu, Jingqi" <jingqi.liu@...el.com>,
Jason Gunthorpe <jgg@...pe.ca>, Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Alex Williamson <alex.williamson@...hat.com>,
Nicolin Chen <nicolinc@...dia.com>
Cc: baolu.lu@...ux.intel.com,
"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH 1/2] iommu: Prevent RESV_DIRECT devices from blocking
domains
On 2023/6/27 15:54, Tian, Kevin wrote:
>> From: Baolu Lu <baolu.lu@...ux.intel.com>
>> Sent: Tuesday, June 13, 2023 11:15 AM
>>
>> On 6/12/23 4:28 PM, Liu, Jingqi wrote:
>>> On 6/7/2023 11:51 AM, Lu Baolu wrote:
>>>> -
>>>> - BUG_ON(!domain->pgsize_bitmap);
>>>> -
>>>> - pg_size = 1UL << __ffs(domain->pgsize_bitmap);
>>>> + pg_size = domain->pgsize_bitmap ? 1UL <<
>>>> __ffs(domain->pgsize_bitmap) : 0;
>>> Would it be better to add the following check here?
>>> if (WARN_ON(!pg_size))
>>> return -EINVAL;
>>>
>>> Instead of checking latter in the loop as follows.
>>> if (WARN_ON_ONCE(!pg_size)) {
>>> ret = -EINVAL;
>>> goto out;
>>> }
>>
>> I am afraid no. Only the paging domains need a valid pg_size. That's the
>> reason why I put it after the iommu_is_dma_domain() check. The previous
>> code has the same behavior too.
>>
>
> You could also add the dma domain check here. pg_size is static
> then it makes more sense to verify it once instead of in a loop.
Agreed. Does below additional change make sense?
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index e59de7852067..3be88b5f36bb 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -962,6 +962,9 @@ static int
iommu_create_device_direct_mappings(struct iommu_domain *domain,
pg_size = domain->pgsize_bitmap ? 1UL <<
__ffs(domain->pgsize_bitmap) : 0;
INIT_LIST_HEAD(&mappings);
+ if (WARN_ON_ONCE((domain->type & __IOMMU_DOMAIN_PAGING) &&
!pg_size))
+ return -EINVAL;
+
iommu_get_resv_regions(dev, &mappings);
/* We need to consider overlapping regions for different devices */
@@ -977,11 +980,6 @@ static int
iommu_create_device_direct_mappings(struct iommu_domain *domain,
!iommu_is_dma_domain(domain))
continue;
- if (WARN_ON_ONCE(!pg_size)) {
- ret = -EINVAL;
- goto out;
- }
-
start = ALIGN(entry->start, pg_size);
end = ALIGN(entry->start + entry->length, pg_size);
Best regards,
baolu
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