linux-kernel - Re: [PATCH v2 1/7] s390/kdump: implement is_kdump

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Message-ID: <20241015100854.7641-J-hca@linux.ibm.com>
Date: Tue, 15 Oct 2024 12:08:54 +0200
From: Heiko Carstens <hca@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-s390@...r.kernel.org, virtualization@...ts.linux.dev,
        linux-doc@...r.kernel.org, kvm@...r.kernel.org,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Thomas Huth <thuth@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Eugenio Pérez <eperezma@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, Mario Casquero <mcasquer@...hat.com>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Mikhail Zaslonko <zaslonko@...ux.ibm.com>
Subject: Re: [PATCH v2 1/7] s390/kdump: implement is_kdump_kernel()

On Tue, Oct 15, 2024 at 10:41:21AM +0200, David Hildenbrand wrote:
> On 15.10.24 10:30, Heiko Carstens wrote:
> > On Mon, Oct 14, 2024 at 09:26:03PM +0200, David Hildenbrand wrote:
> > > On 14.10.24 20:20, Heiko Carstens wrote:
> > > > Looks like this could work. But the comment in smp.c above
> > > > dump_available() needs to be updated.
> > > 
> > > A right, I remember that there was some outdated documentation.

...

> My concern is that we'll now have
> 
> bool is_kdump_kernel(void)
> {
>        return oldmem_data.start && !is_ipl_type_dump();
> }
> 
> Which matches 3), but if 2) is also called "kdump", then should it actually
> be
> 
> bool is_kdump_kernel(void)
> {
>        return oldmem_data.start;
> }
> 
> ?
> 
> When I wrote that code I was rather convinced that the variant in this patch
> is the right thing to do.

Oh well, we simply of too many dump options. I'll let Alexander and
Mikhail better comment on this :)

Alexander, Mikhail, the discussion starts here, and we need a sane
is_kdump_kernel() for s390:
https://lore.kernel.org/all/20241014144622.876731-1-david@redhat.com/