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Subject: Re: [PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find
 all busy IORESOURCE_SYSTEM_RAM resources
To:     linux-kernel@vger.kernel.org
Cc:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Dave Young <dyoung@redhat.com>, Baoquan He <bhe@redhat.com>,
        Vivek Goyal <vgoyal@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Keith Busch <keith.busch@intel.com>,
        Michal Hocko <mhocko@suse.com>, Qian Cai <cai@lca.pw>,
        Oscar Salvador <osalvador@suse.de>,
        Eric Biederman <ebiederm@xmission.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Brijesh Singh <brijesh.singh@amd.com>, x86@kernel.org,
        kexec@lists.infradead.org
References: <20210322160200.19633-1-david@redhat.com>
 <20210322160200.19633-2-david@redhat.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <e4a088e3-fc26-cb59-8af8-a746932b108c@redhat.com>
Date:   Tue, 23 Mar 2021 10:40:33 +0100
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On 22.03.21 17:01, David Hildenbrand wrote:
> It used to be true that we can have busy system RAM only on the first level
> in the resourc tree. However, this is no longer holds for driver-managed
> system RAM (i.e., added via dax/kmem and virtio-mem), which gets added on
> lower levels.
> 
> We have two users of walk_system_ram_res(), which currently only
> consideres the first level:
> a) kernel/kexec_file.c:kexec_walk_resources() -- We properly skip
>     IORESOURCE_SYSRAM_DRIVER_MANAGED resources via
>     locate_mem_hole_callback(), so even after this change, we won't be
>     placing kexec images onto dax/kmem and virtio-mem added memory. No
>     change.
> b) arch/x86/kernel/crash.c:fill_up_crash_elf_data() -- we're currently
>     not adding relevant ranges to the crash elf info, resulting in them
>     not getting dumped via kdump.
> 
> This change fixes loading a crashkernel via kexec_file_load() and including
> dax/kmem and virtio-mem added System RAM in the crashdump on x86-64. Note
> that e.g,, arm64 relies on memblock data and, therefore, always considers
> all added System RAM already.
> 
> Let's find all busy IORESOURCE_SYSTEM_RAM resources, making the function
> behave like walk_system_ram_range().
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> Cc: Signed-off-by: David Hildenbrand <david@redhat.com>

^ My copy-paste action when creating the cc list slipped in a duplicate 
  SO in all 3 patches. I can resend if desired.

-- 
Thanks,

David / dhildenb