From: Aili Yao <yaoaili@kingsoft.com>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>,
"Oscar Salvador" <osalvador@suse.de>,
"david@redhat.com" <david@redhat.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"bp@alien8.de" <bp@alien8.de>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"hpa@zytor.com" <hpa@zytor.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"yangfeng1@kingsoft.com" <yangfeng1@kingsoft.com>,
yaoaili@kingsoft.com
Subject: Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned
Date: Wed, 3 Mar 2021 11:57:10 +0800 [thread overview]
Message-ID: <20210303115710.2e9f8e23@alex-virtual-machine> (raw)
In-Reply-To: <20210303033953.GA205389@agluck-desk2.amr.corp.intel.com>
On Tue, 2 Mar 2021 19:39:53 -0800
"Luck, Tony" <tony.luck@intel.com> wrote:
> On Fri, Feb 26, 2021 at 10:59:15AM +0800, Aili Yao wrote:
> > Hi naoya, tony:
> > > >
> > > > Idea for what we should do next ... Now that x86 is calling memory_failure()
> > > > from user context ... maybe parallel calls for the same page should
> > > > be blocked until the first caller completes so we can:
> > > > a) know that pages are unmapped (if that happens)
> > > > b) all get the same success/fail status
> > >
> > > One memory_failure() call changes the target page's status and
> > > affects all mappings to all affected processes, so I think that
> > > (ideally) we don't have to block other threads (letting them
> > > early return seems fine). Sometimes memory_failure() fails,
> > > but even in such case, PG_hwpoison is set on the page and other
> > > threads properly get SIGBUSs with this patch, so I think that
> > > we can avoid the worst scenario (like system stall by MCE loop).
> > >
> > I agree with naoya's point, if we block for this issue, Does this change the result
> > that the process should be killed? Or is there something other still need to be considered?
>
> Ok ... no blocking ... I think someone in this thread suggested
> scanning the page tables to make sure the poisoned page had been
> unmapped.
>
> There's a walk_page_range() function that does all the work for that.
> Just need to supply some callback routines that check whether a
> mapping includes the bad PFN and clear the PRESENT bit.
>
> RFC patch below against v5.12-rc1
>
> -Tony
>
> From 8de23b7f1be00ad38e129690dfe0b1558fad5ff8 Mon Sep 17 00:00:00 2001
> From: Tony Luck <tony.luck@intel.com>
> Date: Tue, 2 Mar 2021 15:06:33 -0800
> Subject: [PATCH] x86/mce: Handle races between machine checks
>
> When multiple CPUs hit the same poison memory there is a race. The
> first CPU into memory_failure() atomically marks the page as poison
> and continues processing to hunt down all the tasks that map this page
> so that the virtual addresses can be marked not-present and SIGBUS
> sent to the task that did the access.
>
> Later CPUs get an early return from memory_failure() and may return
> to user mode and access the poison again.
>
> Add a new argument to memory_failure() so that it can indicate when
> the race has been lost. Fix kill_me_maybe() to scan page tables in
> this case to unmap pages.
> +
> static void kill_me_now(struct callback_head *ch)
> {
> force_sig(SIGBUS);
> @@ -1257,15 +1304,19 @@ static void kill_me_maybe(struct callback_head *cb)
> {
> struct task_struct *p = container_of(cb, struct task_struct, mce_kill_me);
> int flags = MF_ACTION_REQUIRED;
> + int already = 0;
>
> pr_err("Uncorrected hardware memory error in user-access at %llx", p->mce_addr);
>
> if (!p->mce_ripv)
> flags |= MF_MUST_KILL;
>
> - if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags) &&
> + if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags, &already) &&
> !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) {
> - set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
> + if (already)
> + walk_page_range(current->mm, 0, TASK_SIZE_MAX, &walk, (void *)(p->mce_addr >> PAGE_SHIFT));
> + else
> + set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
> sync_core();
> return;
> MF_MUST_KILL = 1 << 2,
> MF_SOFT_OFFLINE = 1 << 3,
> };
I have one doubt here, when "walk_page_range(current->mm, 0, TASK_SIZE_MAX, &walk, (void *)(p->mce_addr >> PAGE_SHIFT));" is done,
so how is the process triggering this error returned if it have taken the wrong data?
--
Thanks!
Aili Yao
next prev parent reply other threads:[~2021-03-04 0:29 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210224151619.67c29731@alex-virtual-machine>
[not found] ` <20210224103105.GA16368@linux>
[not found] ` <20210225114329.4e1a41c6@alex-virtual-machine>
[not found] ` <20210225112818.GA10141@hori.linux.bs1.fc.nec.co.jp>
[not found] ` <20210225113930.GA7227@localhost.localdomain>
[not found] ` <20210225123806.GA15006@hori.linux.bs1.fc.nec.co.jp>
[not found] ` <20210225181542.GA178925@agluck-desk2.amr.corp.intel.com>
[not found] ` <20210226021907.GA27861@hori.linux.bs1.fc.nec.co.jp>
2021-02-26 2:59 ` [PATCH] mm,hwpoison: return -EBUSY when page already poisoned Aili Yao
2021-03-03 3:39 ` Luck, Tony
2021-03-03 3:57 ` Aili Yao [this message]
2021-03-03 8:39 ` Aili Yao
2021-03-03 15:41 ` Luck, Tony
2021-03-04 2:16 ` Aili Yao
2021-03-04 4:19 ` Aili Yao
2021-03-04 6:45 ` Aili Yao
2021-03-04 23:57 ` Luck, Tony
2021-03-05 1:30 ` Aili Yao
2021-03-05 1:36 ` Aili Yao
2021-03-05 22:11 ` Luck, Tony
2021-03-08 6:45 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-08 18:54 ` Luck, Tony
2021-03-08 22:38 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-08 22:55 ` [PATCH] mm/memory-failure: Use a mutex to avoid memory_failure() races Luck, Tony
2021-03-08 23:42 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-09 2:04 ` Aili Yao
2021-03-09 6:04 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-09 6:35 ` [PATCH v2] mm,hwpoison: return -EBUSY when page already poisoned Aili Yao
2021-03-09 8:28 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-09 20:01 ` Luck, Tony
2021-03-10 8:05 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-13 1:55 ` Jue Wang
2021-03-10 8:01 ` Aili Yao
2021-03-09 6:38 ` [PATCH] mm/memory-failure: Use a mutex to avoid memory_failure() races Aili Yao
2021-03-05 15:55 ` [PATCH] mm,hwpoison: return -EBUSY when page already poisoned Luck, Tony
2021-03-10 6:10 ` Aili Yao
2021-03-11 8:55 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-11 11:23 ` Aili Yao
2021-03-11 17:05 ` Luck, Tony
2021-03-12 5:55 ` Aili Yao
2021-03-12 16:29 ` Luck, Tony
2021-03-12 23:48 ` Luck, Tony
2021-03-16 6:42 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-16 7:54 ` Aili Yao
2021-03-17 0:29 ` Luck, Tony
2021-03-17 9:07 ` Aili Yao
2021-03-17 7:48 ` Aili Yao
2021-03-17 8:23 ` Aili Yao
[not found] ` <20210226105250.3a15e35c@alex-virtual-machine>
2021-02-26 17:58 ` Luck, Tony
2021-03-02 4:32 ` Aili Yao
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=20210303115710.2e9f8e23@alex-virtual-machine \
--to=yaoaili@kingsoft.com \
--cc=akpm@linux-foundation.org \
--cc=bp@alien8.de \
--cc=david@redhat.com \
--cc=hpa@zytor.com \
--cc=linux-edac@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@redhat.com \
--cc=naoya.horiguchi@nec.com \
--cc=osalvador@suse.de \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
--cc=yangfeng1@kingsoft.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).