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Date: Mon, 21 Feb 2022 01:32:16 +0000
From: HORIGUCHI NAOYA(堀口 直也)
<naoya.horiguchi@....com>
To: luofei <luofei@...cloud.com>
CC: "tony.luck@...el.com" <tony.luck@...el.com>,
"bp@...en8.de" <bp@...en8.de>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"x86@...nel.org" <x86@...nel.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"hpa@...or.com" <hpa@...or.com>,
"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v3 1/2] hw/poison: Avoid the impact of hwpoison_filter()
return value on mce handler
Conventionally, "hwpoison" or "HWPOISON" (instead of "hw/poison") is used in
the subsystem tag in $SUBJECT, so could you align it (for grep friendliness) ?
# I should've mentioned this in previous review round, sorry.
On Fri, Feb 18, 2022 at 04:40:56AM -0500, luofei wrote:
> When the hwpoison page meets the filter conditions, it should
> not be regarded as successful memory_failure() processing for
> mce handler, but should return a value(-EHWPOISON), otherwise
> mce handler regards the error page has been identified and
> isolated, which may lead to calling set_mce_nospec() to change
> page attribute, etc.
>
> Here a new MF_MCE__HANDLE flag is introdulced to identify the
^^ ^^^^^^^^^^^
single '_' ? introduced
> call from the mce handler and instruct hwpoison_filter() to
> return -EHWPOISON, other return 0 for compatibility with the
^^^^^
otherwise ?
> hwpoison injector.
>
> Signed-off-by: luofei <luofei@...cloud.com>
The diff looks ok to me, so with updates on the subject/description ...
Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
Thanks,
Naoya Horiguchi
> ---
> arch/x86/kernel/cpu/mce/core.c | 15 +++++++++------
> include/linux/mm.h | 1 +
> mm/memory-failure.c | 14 ++++++++++++--
> 3 files changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 5818b837fd4d..de29165c65b6 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -612,7 +612,7 @@ static int uc_decode_notifier(struct notifier_block *nb, unsigned long val,
> return NOTIFY_DONE;
>
> pfn = mce->addr >> PAGE_SHIFT;
> - if (!memory_failure(pfn, 0)) {
> + if (!memory_failure(pfn, MF_MCE_HANDLE)) {
> set_mce_nospec(pfn, whole_page(mce));
> mce->kflags |= MCE_HANDLED_UC;
> }
> @@ -1286,7 +1286,7 @@ static void kill_me_now(struct callback_head *ch)
> 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 flags = MF_ACTION_REQUIRED | MF_MCE_HANDLE;
> int ret;
>
> p->mce_count = 0;
> @@ -1303,9 +1303,12 @@ static void kill_me_maybe(struct callback_head *cb)
> }
>
> /*
> - * -EHWPOISON from memory_failure() means that it already sent SIGBUS
> - * to the current process with the proper error info, so no need to
> - * send SIGBUS here again.
> + * -EHWPOISON from memory_failure() means that memory_failure() did
> + * not handle the error event for the following reason:
> + * - SIGBUS has already been sent to the current process with the
> + * proper error info, or
> + * - hwpoison_filter() filtered the event,
> + * so no need to deal with it more.
> */
> if (ret == -EHWPOISON)
> return;
> @@ -1320,7 +1323,7 @@ static void kill_me_never(struct callback_head *cb)
>
> p->mce_count = 0;
> pr_err("Kernel accessed poison in user space at %llx\n", p->mce_addr);
> - if (!memory_failure(p->mce_addr >> PAGE_SHIFT, 0))
> + if (!memory_failure(p->mce_addr >> PAGE_SHIFT, MF_MCE_HANDLE))
> set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
> }
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 213cc569b192..f4703f948e9a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3188,6 +3188,7 @@ enum mf_flags {
> MF_MUST_KILL = 1 << 2,
> MF_SOFT_OFFLINE = 1 << 3,
> MF_UNPOISON = 1 << 4,
> + MF_MCE_HANDLE = 1 << 5,
> };
> extern int memory_failure(unsigned long pfn, int flags);
> extern void memory_failure_queue(unsigned long pfn, int flags);
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 97a9ed8f87a9..59d6d939a752 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1526,7 +1526,10 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
> if (TestClearPageHWPoison(head))
> num_poisoned_pages_dec();
> unlock_page(head);
> - return 0;
> + if (flags & MF_MCE_HANDLE)
> + return -EHWPOISON;
> + else
> + return 0;
> }
> unlock_page(head);
> res = MF_FAILED;
> @@ -1613,7 +1616,10 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> goto out;
>
> if (hwpoison_filter(page)) {
> - rc = 0;
> + if (flags & MF_MCE_HANDLE)
> + rc = -EHWPOISON;
> + else
> + rc = 0;
> goto unlock;
> }
>
> @@ -1837,6 +1843,10 @@ int memory_failure(unsigned long pfn, int flags)
> num_poisoned_pages_dec();
> unlock_page(p);
> put_page(p);
> + if (flags & MF_MCE_HANDLE)
> + res = -EHWPOISON;
> + else
> + res = 0;
> goto unlock_mutex;
> }
>
> --
> 2.27.0
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