From: Dave Young <dyoung@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, pasha.tatashin@oracle.com,
linux-mm@kvack.org, akpm@linux-foundation.org
Subject: Re: [PATCH] mm: check pfn_valid first in zero_resv_unavail
Date: Fri, 1 Dec 2017 17:49:39 +0800 [thread overview]
Message-ID: <20171201094939.GA3335@dhcp-128-65.nay.redhat.com> (raw)
In-Reply-To: <20171201094215.aenoqa5jepdc3jd5@dhcp22.suse.cz>
On 12/01/17 at 10:42am, Michal Hocko wrote:
> On Fri 01-12-17 17:29:51, Dave Young wrote:
> > On 12/01/17 at 10:19am, Michal Hocko wrote:
> > > On Fri 01-12-17 16:56:57, Dave Young wrote:
> > > > On 11/30/17 at 10:35am, Michal Hocko wrote:
> > > [...]
> > > > > Can we exclude that range from the memblock allocator instead? E.g. what
> > > > > happens if somebody allocates from that range?
> > > >
> > > > It is a EFI BGRT image buffer provided by firmware, they are reserved
> > > > always and can not be used to allocate memory.
> > >
> > > Hmm, I see but I was actually suggesting to remove this range from the
> > > memblock allocator altogether (memblock_remove) as it shouldn't be there
> > > in the first place.
> >
> > Oh, I'm not sure because it is introduced as a way for efi to reserve
> > boot services areas to be persistent across kexec reboot. See
> > drivers/firmware/efi/efi.c: efi_mem_reserve(), BGRT is only one user
> > of it, there is esrt and maybe other users, I do not know if it is safe
> > :(
>
> Hmm, so it this range ever backed by a valid pfn?
I think it is in normal boot, just it does not appear in e820 across kdump
reboot. For kdump kexec_tools provided e820 the last pfn only covers the kdump
crashkernel ranges thus it is not mapped.
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2017-12-01 9:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 6:04 [PATCH] mm: check pfn_valid first in zero_resv_unavail Dave Young
2017-11-30 9:35 ` Michal Hocko
2017-12-01 8:56 ` Dave Young
2017-12-01 9:19 ` Michal Hocko
2017-12-01 9:29 ` Dave Young
2017-12-01 9:42 ` Michal Hocko
2017-12-01 9:49 ` Dave Young [this message]
2017-11-30 17:25 ` Pavel Tatashin
2017-12-01 8:57 ` Dave Young
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