linux-kernel - Re: Re: [PATCH 2/3] mm/memory-failure.c: support reset PTE during unpoison

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <286dbd1f-1c62-a171-7453-d772bd98332c@bytedance.com>
Date:   Mon, 30 May 2022 13:46:57 +0800
From:   zhenwei pi <pizhenwei@...edance.com>
To:     HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>
Cc:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mst@...hat.com" <mst@...hat.com>,
        "david@...hat.com" <david@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>
Subject: Re: Re: [PATCH 2/3] mm/memory-failure.c: support reset PTE during
 unpoison



On 5/30/22 13:02, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Fri, May 20, 2022 at 03:06:47PM +0800, zhenwei pi wrote:
>> Origianlly, unpoison_memory() is only used by hwpoison-inject, and
>> unpoisons a page which is poisoned by hwpoison-inject too. The kernel PTE
>> entry has no change during software poison/unpoison.
>>
>> On a virtualization platform, it's possible to fix hardware corrupted page
>> by hypervisor, typically the hypervisor remaps the error HVA(host virtual
>> address). So add a new parameter 'const char *reason' to show the reason
>> called by.
>>
>> Once the corrupted page gets fixed, the guest kernel needs put page to
>> buddy. Reuse the page and hit the following issue(Intel Platinum 8260):
>>   BUG: unable to handle page fault for address: ffff888061646000
>>   #PF: supervisor write access in kernel mode
>>   #PF: error_code(0x0002) - not-present page
>>   PGD 2c01067 P4D 2c01067 PUD 61aaa063 PMD 10089b063 PTE 800fffff9e9b9062
>>   Oops: 0002 [#1] PREEMPT SMP NOPTI
>>   CPU: 2 PID: 31106 Comm: stress Kdump: loaded Tainted: G   M       OE     5.18.0-rc6.bm.1-amd64 #6
>>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>>   RIP: 0010:clear_page_erms+0x7/0x10
>>
>> The kernel PTE entry of the fixed page is still uncorrected, kernel hits
>> page fault during prep_new_page. So add 'bool reset_kpte' to get a change
>> to fix the PTE entry if the page is fixed by hypervisor.
>>
>> Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
>> ---
>>   include/linux/mm.h   |  2 +-
>>   mm/hwpoison-inject.c |  2 +-
>>   mm/memory-failure.c  | 26 +++++++++++++++++++-------
>>   3 files changed, 21 insertions(+), 9 deletions(-)
>>
> 
> Do you need undoing rate limiting here?  In the original unpoison's usage,
> avoiding flood of "Unpoison: Software-unpoisoned page" messages is helpful.
> 
> And unpoison seems to be called from virtio-balloon multiple times when
> the backend is 2MB hugepages.  If it's right, printing out 512 lines of
> "Unpoison: Unpoisoned page 0xXXX by virtio-balloon" messages might not be
> so helpful?
> 

All the suggestions(include '[PATCH 1/3] memory-failure: Introduce 
memory failure notifier') are reasonable, I'll fix them in the next 
version. Thanks a lot!


-- 
zhenwei pi