linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: cai@lca.pw, mhocko@suse.com, ira.weiny@intel.com,
	david@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com,
	linux-kernel@vger.kernel.org, logang@deltatee.com,
	james.morse@arm.com, cpandya@codeaurora.org,
	arunks@codeaurora.org, akpm@linux-foundation.org,
	osalvador@suse.de, mgorman@techsingularity.net,
	dan.j.williams@intel.com, linux-arm-kernel@lists.infradead.org,
	robin.murphy@arm.com
Subject: Re: [PATCH V3 2/4] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump
Date: Wed, 15 May 2019 07:26:32 +0530	[thread overview]
Message-ID: <107ce10f-622c-7914-6269-cff5509b084f@arm.com> (raw)
In-Reply-To: <20190514154000.GA20935@lakrids.cambridge.arm.com>



On 05/14/2019 09:10 PM, Mark Rutland wrote:
> On Tue, May 14, 2019 at 02:30:05PM +0530, Anshuman Khandual wrote:
>> The arm64 pagetable dump code can race with concurrent modification of the
>> kernel page tables. When a leaf entries are modified concurrently, the dump
>> code may log stale or inconsistent information for a VA range, but this is
>> otherwise not harmful.
>>
>> When intermediate levels of table are freed, the dump code will continue to
>> use memory which has been freed and potentially reallocated for another
>> purpose. In such cases, the dump code may dereference bogus addressses,
>> leading to a number of potential problems.
>>
>> Intermediate levels of table may by freed during memory hot-remove, or when
>> installing a huge mapping in the vmalloc region. To avoid racing with these
>> cases, take the memory hotplug lock when walking the kernel page table.
>>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> Can we please move this after the next patch (which addresses the huge
> vmap case), and change the last paragraph to:
> 
>   Intermediate levels of table may by freed during memory hot-remove,
>   which will be enabled by a subsequent patch. To avoid racing with
>   this, take the memory hotplug lock when walking the kernel page table.
> 
> With that, this looks good to me.

Sure will do.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2019-05-15  1:56 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-14  9:00 [PATCH V3 0/4] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-05-14  9:00 ` [PATCH V3 1/4] mm/hotplug: Reorder arch_remove_memory() call in __remove_memory() Anshuman Khandual
2019-05-14  9:05   ` David Hildenbrand
2019-05-14  9:00 ` [PATCH V3 2/4] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Anshuman Khandual
2019-05-14  9:16   ` David Hildenbrand
2019-05-14 15:40   ` Mark Rutland
2019-05-15  1:56     ` Anshuman Khandual [this message]
2019-05-15 16:58   ` Michal Hocko
2019-05-16 10:23     ` Mark Rutland
2019-05-16 11:05       ` Michal Hocko
2019-05-22 16:42         ` Mark Rutland
2019-05-24  6:06           ` Anshuman Khandual
2019-05-27  7:20           ` Michal Hocko
2019-05-28 14:09             ` Mark Rutland
2019-05-16 11:06       ` Anshuman Khandual
2019-05-16 11:16         ` Michal Hocko
2019-05-23  8:40           ` David Hildenbrand
2019-05-24  5:43             ` Anshuman Khandual
2019-05-14  9:00 ` [PATCH V3 3/4] arm64/mm: Inhibit huge-vmap with ptdump Anshuman Khandual
2019-05-14  9:20   ` David Hildenbrand
2019-05-16  8:38   ` Ard Biesheuvel
2019-05-14  9:00 ` [PATCH V3 4/4] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-05-14  9:08   ` David Hildenbrand
2019-05-15 11:49   ` Mark Rutland
2019-05-16  5:34     ` Anshuman Khandual
2019-05-16 10:57       ` Mark Rutland
2019-05-17  3:15         ` Anshuman Khandual
2019-05-14  9:10 ` [PATCH V3 0/4] " David Hildenbrand

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=107ce10f-622c-7914-6269-cff5509b084f@arm.com \
    --to=anshuman.khandual@arm.com \
    --cc=akpm@linux-foundation.org \
    --cc=arunks@codeaurora.org \
    --cc=cai@lca.pw \
    --cc=catalin.marinas@arm.com \
    --cc=cpandya@codeaurora.org \
    --cc=dan.j.williams@intel.com \
    --cc=david@redhat.com \
    --cc=ira.weiny@intel.com \
    --cc=james.morse@arm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=logang@deltatee.com \
    --cc=mark.rutland@arm.com \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@suse.com \
    --cc=osalvador@suse.de \
    --cc=robin.murphy@arm.com \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).