linux-kernel - Re: [PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find all busy IORESOURCE_SYSTEM

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Message-ID: <YFnL8q6X97T3xAp6@smile.fi.intel.com>
Date:   Tue, 23 Mar 2021 13:07:30 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Keith Busch <keith.busch@...el.com>,
        Michal Hocko <mhocko@...e.com>, Qian Cai <cai@....pw>,
        Oscar Salvador <osalvador@...e.de>,
        Eric Biederman <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>, x86@...nel.org,
        kexec@...ts.infradead.org
Subject: Re: [PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find
 all busy IORESOURCE_SYSTEM_RAM resources

On Tue, Mar 23, 2021 at 10:40:33AM +0100, David Hildenbrand wrote:
> 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@...ux-foundation.org>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> > Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> > Cc: Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> ^ My copy-paste action when creating the cc list slipped in a duplicate  SO
> in all 3 patches. I can resend if desired.

I think to address my comments you will need to resend anyway (as v2).

-- 
With Best Regards,
Andy Shevchenko