From: Aili Yao <yaoaili@kingsoft.com>
To: Oscar Salvador <osalvador@suse.de>, <naoya.horiguchi@nec.com>,
<tony.luck@intel.com>, <david@redhat.com>
Cc: <akpm@linux-foundation.org>, <bp@alien8.de>, <tglx@linutronix.de>,
<mingo@redhat.com>, <hpa@zytor.com>, <x86@kernel.org>,
<inux-edac@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-mm@kvack.org>, <yangfeng1@kingsoft.com>,
<yaoaili@kingsoft.com>
Subject: Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned
Date: Thu, 25 Feb 2021 11:43:29 +0800 [thread overview]
Message-ID: <20210225114329.4e1a41c6@alex-virtual-machine> (raw)
In-Reply-To: <20210224103105.GA16368@linux>
On Wed, 24 Feb 2021 11:31:55 +0100
Oscar Salvador <osalvador@suse.de> wrote:
> I have some questions:
>
> > 1.When LCME is enabled, and there are two processes A && B running on
> > different core X && Y separately, which will access one same page, then
> > the page corrupted when process A access it, a MCE will be rasied to
> > core X and the error process is just underway.
>
> When !LMCE, that is not a problem because new MCE needs to wait for the ongoing MCE?
I am not sure whether this case will happen when !LMCE, when I realized this place may be an issue
I tried to reproduce it and my configuration is LMCE enabled.
> > 2.Then B access the page and trigger another MCE to core Y, it will also
> > do error process, it will see TestSetPageHWPoison be true, and 0 is
> > returned.
>
> For non-nested calls, that is no problem because the page will be taken out
> of business(unmapped from the processes), right? So no more MCE are possible.
Yes, I think after the recovery jod is finished, other processes still access the page
will meet a page fault and error will be returned;
> >
> > 3.The kill_me_maybe will check the return:
> >
> > 1244 static void kill_me_maybe(struct callback_head *cb)
> > 1245 {
> >
> > 1254 if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags) &&
> > 1255 !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) {
> > 1256 set_mce_nospec(p->mce_addr >> PAGE_SHIFT,
>
> So, IIUC, in case of a LMCE nested call, the second MCE will reach here.
> set_mce_nospec() will either mark the underlying page as not mapped/cached.
>
This set_mce_nospec() is not proper when the recovery job is on the fly. In my test
this function failed.
> Should not have memory_failure()->hwpoison_user_mappings() unmapped the page
> from both process A and B? Or this is in case the ongoing MCE(process A) has
> not still unmapped anything, so process B can still access this page.
>
What I care is the process B triggered the error again after process A,
I don't know how it return and proceed.
> So with your change, process B will be sent a SIGBUG, while process A is still
> handling the MCE, right?
Right!
> > p->mce_whole_page);
> > 1257 sync_core();
> > 1258 return;
> > 1259 }
> >
> > 1267 }
> >
> > 4. The error process for B will end, and may nothing happened if
> > kill-early is not set, We may let the wrong data go into effect.
> >
> > For other cases which care the return value of memory_failure() should
> > check why they want to process a memory error which have already been
> > processed. This behavior seems reasonable.
> >
> > In kill_me_maybe, log the fact about the memory may not recovered, and
> > we will kill the related process.
> >
> > Signed-off-by: Aili Yao <yaoaili@kingsoft.com>
> > ---
> > arch/x86/kernel/cpu/mce/core.c | 2 ++
> > mm/memory-failure.c | 4 ++--
> > 2 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> > index e133ce1e562b..db4afc5bf15a 100644
> > --- a/arch/x86/kernel/cpu/mce/core.c
> > +++ b/arch/x86/kernel/cpu/mce/core.c
> > @@ -1259,6 +1259,8 @@ static void kill_me_maybe(struct callback_head *cb)
> > }
> >
> > if (p->mce_vaddr != (void __user *)-1l) {
> > + pr_err("Memory error may not recovered: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> > + p->mce_addr >> PAGE_SHIFT, p->comm, p->pid);
> > force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT);
> > } else {
> > pr_err("Memory error not recovered");
> > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> > index e9481632fcd1..06f006174b8c 100644
> > --- a/mm/memory-failure.c
> > +++ b/mm/memory-failure.c
> > @@ -1224,7 +1224,7 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
> > if (TestSetPageHWPoison(head)) {
> > pr_err("Memory failure: %#lx: already hardware poisoned\n",
> > pfn);
> > - return 0;
> > + return -EBUSY;
>
> As David said, madvise_inject_error() will start returning -EBUSY now in case
> we madvise(MADV_HWPOISON) on an already hwpoisoned page.
>
> AFAICS, memory_failure() can return 0, -Eerrors, and MF_XXX.
> Would it make sense to unify that? That way we could declare error codes that
> make somse sense (like MF_ALREADY_HWPOISONED).
>
@David:
I checked the code again, and find a few places will care the exact return value, like:
1: drivers/base/memory.c:483: ret = memory_failure(pfn, 0);
This is for hard page offline, I see the code in mcelog:
static void offline_action(struct mempage *mp, u64 addr)
{
if (offline <= OFFLINE_ACCOUNT)
return;
Lprintf("Offlining page %llx\n", addr);
if (memory_offline(addr) < 0) {
Lprintf("Offlining page %llx failed: %s\n", addr, strerror(errno));
mp->offlined = PAGE_OFFLINE_FAILED;
} else
mp->offlined = PAGE_OFFLINE;
}
I think return an negative value will be more proper? As the related killing function may not be performed, and we can't say
it's a success operation?
2:mm/hwpoison-inject.c:51: return memory_failure(pfn, 0);
mm/madvise.c:910: ret = memory_failure(pfn, MF_COUNT_INCREASED);
These two cases are mainly for error injections, I checked the test codes, mostly it only care if the value is 0 or < 0;
I do the related test, normally it work well, but for stress test, sometimes in some case, I do meet some fail cases along with the -EBUSY return.
I will dig more.
Other place will only care if the return value is 0. or just ignore it.
Hi naoya, what's your opnion for this possible issue, I need your inputs!
Thanks
Aili Yao
next prev parent reply other threads:[~2021-02-25 3:43 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-24 7:16 [PATCH] mm,hwpoison: return -EBUSY when page already poisoned Aili Yao
2021-02-24 10:10 ` David Hildenbrand
2021-02-24 10:31 ` Oscar Salvador
2021-02-25 3:43 ` Aili Yao [this message]
2021-02-25 11:28 ` HORIGUCHI NAOYA(堀口 直也)
2021-02-25 11:39 ` Oscar Salvador
2021-02-25 12:38 ` HORIGUCHI NAOYA(堀口 直也)
2021-02-25 18:15 ` Luck, Tony
2021-02-26 2:19 ` HORIGUCHI NAOYA(堀口 直也)
2021-02-26 2:59 ` Aili Yao
2021-03-03 3:39 ` Luck, Tony
2021-03-03 3:57 ` Aili Yao
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)
[not found] ` <20210309100421.3d09b6b1@alex-virtual-machine>
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
2021-03-31 11:25 ` [PATCH v3] mm,hwpoison: return -EHWPOISON " Aili Yao
2021-04-01 15:33 ` Luck, Tony
2021-04-02 1:18 ` Aili Yao
2021-04-02 15:11 ` Luck, Tony
2021-04-05 13:50 ` HORIGUCHI NAOYA(堀口 直也)
2021-04-06 1:04 ` 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
2021-02-26 3:26 ` Tony Luck
2021-02-26 2:52 ` Aili Yao
2021-02-26 17:58 ` Luck, Tony
2021-03-02 4:32 ` Aili Yao
2021-03-31 10:56 ` Aili Yao
2021-03-31 10:58 ` David Hildenbrand
2021-03-01 23:21 Jue Wang
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