Re: [PATCH v2 5/7] virtio-mem: s390 support

David Hildenbrand
2024-10-14T19:16:51Z

On 14.10.24 20:48, Heiko Carstens wrote:
> On Mon, Oct 14, 2024 at 04:46:17PM +0200, David Hildenbrand wrote:
>> The special s390 kdump mode, whereby the 2nd kernel creates the ELF
>> core header, won't currently dump virtio-mem memory. The virtio-mem
>> driver has a special kdump mode, from where we can detect memory ranges
>> to dump. Based on this, support for dumping virtio-mem memory can be
>> added in the future fairly easily.
>

Thanks for the review.

> Hm.. who will add this support? This looks like a showstopper to me.

The cover letter is clearer on that: "One remaining work item is kdump
support for virtio-mem memory. This will be sent out separately once
initial support landed."

I had a prototype, but need to spend some time to clean it up -- or find
someone to hand it over to clean it up.

I have to chose wisely what I work on nowadays, and cannot spend that
time if the basic support won't get ACKed.

> Who is supposed to debug crash dumps where memory parts are missing?

For many production use cases it certainly needs to exist.

But note that virtio-mem can be used with ZONE_MOVABLE, in which case
mostly only user data (e.g., pagecache,anon) ends up on hotplugged
memory, that would get excluded from makedumpfile in the default configs
either way.

It's not uncommon to let kdump support be added later (e.g., AMD SNP
variants).

--
Cheers,

David / dhildenb