From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Dan Williams <dan.j.williams@intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mike Rapoport <rppt@linux.ibm.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Oscar Salvador <osalvador@suse.de>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Pavel Tatashin <pavel.tatashin@microsoft.com>,
Pingfan Liu <kernelfans@gmail.com>, Qian Cai <cai@lca.pw>,
Vlastimil Babka <vbabka@suse.cz>,
Wei Yang <richard.weiyang@gmail.com>
Subject: Re: [PATCH v2 0/2] mm: Memory offlining + page isolation cleanups
Date: Tue, 22 Oct 2019 11:17:24 +0200 [thread overview]
Message-ID: <68d6da35-276c-0491-99ea-8249dee8fd1d@redhat.com> (raw)
In-Reply-To: <20191022091431.GG9379@dhcp22.suse.cz>
On 22.10.19 11:14, Michal Hocko wrote:
> On Tue 22-10-19 10:32:11, David Hildenbrand wrote:
> [...]
>> E.g., arch/x86/kvm/mmu.c:kvm_is_mmio_pfn()
>
> Thanks for these references. I am not really familiar with kvm so I
> cannot really comment on the specific code but I am wondering why
> it simply doesn't check for ZONE_DEVICE explicitly? Also we do care
> about holes in RAM (from the early boot), those should be reserved
> already AFAIR. So we are left with hotplugged memory with holes and
> I am not really sure we should bother with this until there is a clear
> usecase in sight.
Well, checking for ZONE_DEVICE is only possible if you have an
initialized memmap. And that is not guaranteed when you start mapping
random stuff into your guest via /dev/mem.
I am reworking these patches right now and audit the whole kernel for
PageReserved() checks that might affect ZONE_DEVICE. I'll send the
collection of patches as RFC.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-10-22 9:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-21 17:23 David Hildenbrand
2019-10-21 17:23 ` [PATCH v2 1/2] mm/page_alloc.c: Don't set pages PageReserved() when offlining David Hildenbrand
2019-10-21 17:23 ` [PATCH v2 2/2] mm/page_isolation.c: Convert SKIP_HWPOISON to MEMORY_OFFLINE David Hildenbrand
2019-10-22 6:52 ` [PATCH v2 0/2] mm: Memory offlining + page isolation cleanups David Hildenbrand
2019-10-22 8:08 ` Michal Hocko
2019-10-22 8:15 ` David Hildenbrand
2019-10-22 8:21 ` Michal Hocko
2019-10-22 8:32 ` David Hildenbrand
2019-10-22 8:38 ` David Hildenbrand
2019-10-22 9:14 ` Michal Hocko
2019-10-22 9:17 ` David Hildenbrand [this message]
2019-10-22 9:24 ` Michal Hocko
2019-10-22 9:27 ` David Hildenbrand
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