Re: [PATCH 0/2] iommu/amd: Fix device table setup in kdump kernels

[Matt Fleming <mfleming@cloudflare.com>]

On Fri, Oct 02, 2026 at 02:31:41PM +0100, Matt Fleming wrote:
> From: Matt Fleming <mfleming@cloudflare.com>
> 
> An AMD kdump kernel booted with crashkernel=512M,high and
> crashkernel=0,low fails to allocate its device table because there's no
> memory below 4G. IOMMU init fails and, on our systems with an Intel
> E810 NIC, the ice driver's TX queues time out, so the dump never gets
> sent.
> 
> Since commit 38e5f33ee359 ("iommu/amd: Reuse device table for kdump"), a
> kdump kernel normally reuses the previous kernel's table. Patch 1
> programs the new table if reuse fails. Patch 2 drops GFP_DMA32 for
> kdump kernels. Normal kernels still allocate below 4G, because that's
> what the kdump kernel checks before reusing the table.
> 
> On an AMD EPYC system with an E810 NIC, the kdump kernel without these
> patches failed the order-9 GFP_DMA32 allocation and its TX queues timed
> out. With these patches, the kdump kernel reused the old device table
> and the dump was written over the network.
> 
> Matt Fleming (2):
>   iommu/amd: Program device table when kdump reuse fails
>   iommu/amd: Don't allocate kdump device table from DMA32
> 
>  drivers/iommu/amd/init.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)

Hey Joerg, 

I know it was Plumbers and ksummit this week, but have you had chance
to look at these two patches?

Thanks,
Matt