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

[Suravee Suthikulpanit]

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@xxxxxxxxxx> 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