linux-kernel - Re: "Convert the AMD iommu driver to the dma-iommu api" is buggy

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Date:   Wed, 16 Oct 2019 17:09:20 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Joerg Roedel <jroedel@...e.de>, Qian Cai <cai@....pw>
Cc:     iommu@...ts.linux-foundation.org, Christoph Hellwig <hch@....de>,
        Tom Murphy <murphyt7@....ie>, linux-kernel@...r.kernel.org,
        Julien Grall <julien.grall@....com>,
        Marc Zyngier <maz@...nel.org>
Subject: Re: "Convert the AMD iommu driver to the dma-iommu api" is buggy

On 16/10/2019 17:03, Joerg Roedel wrote:
> On Wed, Oct 16, 2019 at 11:53:33AM -0400, Qian Cai wrote:
>> On Wed, 2019-10-16 at 17:31 +0200, Joerg Roedel wrote:
> 
>> The x86 one might just be a mistake.
>>
>> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
>> index ad05484d0c80..63c4b894751d 100644
>> --- a/drivers/iommu/amd_iommu.c
>> +++ b/drivers/iommu/amd_iommu.c
>> @@ -2542,7 +2542,7 @@ static int amd_iommu_map(struct iommu_domain *dom,
>> unsigned long iova,
>>          if (iommu_prot & IOMMU_WRITE)
>>                  prot |= IOMMU_PROT_IW;
>>   
>> -       ret = iommu_map_page(domain, iova, paddr, page_size, prot, GFP_KERNEL);
>> +       ret = iommu_map_page(domain, iova, paddr, page_size, prot, gfp);
> 
> Yeah, that is a bug, I spotted that too.
> 
>> @@ -1185,7 +1185,7 @@ static struct iommu_dma_msi_page
>> *iommu_dma_get_msi_page(struct device *dev,
>>          if (!iova)
>>                  goto out_free_page;
>>   
>> -       if (iommu_map(domain, iova, msi_addr, size, prot))
>> +       if (iommu_map_atomic(domain, iova, msi_addr, size, prot))
>>                  goto out_free_iova;
> 
> Not so sure this is a bug, this code is only about setting up MSIs on
> ARM. It probably doesn't need to be atomic.
Right, since the iommu_dma_prepare_msi() operation was broken out to 
happen at MSI domain setup time, I don't think the comment in there 
applies any more, so we can probably stop disabling irqs around the 
iommu_dma_get_msi_page() call.

Robin.