Re: [PATCH v2] powerpc/pseries: Don't enforce MSI affinity with kdump

On Mon, 15 Feb 2021 10:45:06 +0100, Greg Kurz wrote:

Depending on the number of online CPUs in the original kernel, it is
likely for CPU #0 to be offline in a kdump kernel. The associated IRQs
in the affinity mappings provided by irq_create_affinity_masks() are
thus not started by irq_startup(), as per-design with managed IRQs.

This can be a problem with multi-queue block devices driven by blk-mq :
such a non-started IRQ is very likely paired with the single queue
enforced by blk-mq during kdump (see blk_mq_alloc_tag_set()). This
causes the device to remain silent and likely hangs the guest at
some point.

[...]

Applied to powerpc/fixes.

[1/1] powerpc/pseries: Don't enforce MSI affinity with kdump
      https://git.kernel.org/powerpc/c/f9619d5e5174867536b7e558683bc4408eab833f

cheers