linux-kernel - Re: [GIT PULL] IOMMU fix for 5.10 (-final)

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Date:   Thu, 10 Dec 2020 18:55:03 +0700
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     Will Deacon <will@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     iommu <iommu@...ts.linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [GIT PULL] IOMMU fix for 5.10 (-final)

Hi All,

On 12/10/20 1:50 AM, Will Deacon wrote:
> On Wed, Dec 09, 2020 at 10:07:46AM -0800, Linus Torvalds wrote:
>> On Wed, Dec 9, 2020 at 6:12 AM Will Deacon <will@...nel.org> wrote:
>>>
>>> Please pull this one-liner AMD IOMMU fix for 5.10. It's actually a fix
>>> for a fix, where the size of the interrupt remapping table was increased
>>> but a related constant for the size of the interrupt table was forgotten.
>>
>> Pulled.
> 
> Thanks.
> 
>> However, why didn't this then add some sanity checking for the two
>> different #defines to be in sync?
>>
>> IOW, something like
>>
>>     #define AMD_IOMMU_IRQ_TABLE_SHIFT 9
>>
>>     #define MAX_IRQS_PER_TABLE (1 << AMD_IOMMU_IRQ_TABLE_SHIFT)
>>     #define DTE_IRQ_TABLE_LEN ((u64)AMD_IOMMU_IRQ_TABLE_SHIFT << 1)
>>
>> or whatever. Hmm?
> 
> This looks like a worthwhile change to me, but I don't have any hardware
> so I've been very reluctant to make even "obvious" driver changes here.
> 
> Suravee -- please can you post a patch implementing the above?

I'll send one out ASAP.

> 
>> That way this won't happen again, but perhaps equally importantly the
>> linkage will be more clear, and there won't be those random constants.
>>
>> Naming above is probably garbage - I assume there's some actual
>> architectural name for that irq table length field in the DTE?
> 
> The one in the spec is even better: "IntTabLen".
> 
> Will

Thanks,
Suravee