Re: [PATCH v7 0/2] iommu/arm-smmu-v3: Make the queue depths tunable, and shrink them in a kdump kernel

[Jason Gunthorpe]

On Fri, Sep 25, 2026 at 03:15:28PM +0100, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>
> 
> The queues are sized from the IDR1 maxima and allocated at probe, costing
> megabytes per queue per SMMU instance. A kdump capture kernel pays that out
> of a small crashkernel reservation, for queues it barely uses and two of
> which it switches off anyway.
> 
> Patch 1 adds a cmdq_max_n_shift module parameter, decided in a per-queue
> helper and floored at one page. Patch 2 has a kdump kernel size all three
> queues at one page through the same helper. The parameter does not apply
> there.

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason