On Wed, Feb 16, 2022 at 10:00:38PM -0500, luofei wrote:
> After successfully obtaining the reference count of the huge
> page, it is still necessary to call hwpoison_filter() to make a
> filter judgement, otherwise the filter hugepage will be unmaped
> and the related process may be killed.
>
> Also when the huge page meets the filter conditions, it should
> not be regarded as successful memory_failure() processing for
> mce handler, but should return a value to inform the caller,
> otherwise the caller regards the error page has been identified
> and isolated, which may lead to calling set_mce_nospec() to change
> page attribute, etc.
>
> Signed-off-by: luofei <luofei@xxxxxxxxxxxx>
This patch seems to do two separate things (introducing MF_MCE_HANDLE,
and adding hwpoison_filter() in memory_failure_hugetlb()), so could you
separate the patch into two?
> ---
> arch/x86/kernel/cpu/mce/core.c | 22 +++++++++++-----------
> include/linux/mm.h | 1 +
> mm/memory-failure.c | 25 +++++++++++++++++++++++--
> 3 files changed, 35 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 5818b837fd4d..c2b99c60225f 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;
> @@ -1300,14 +1300,14 @@ static void kill_me_maybe(struct callback_head *cb)
> set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
> sync_core();
> return;
> - }
> -
> - /*
> - * -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.
> - */
> - if (ret == -EHWPOISON)
> + } else if (ret == -EHWPOISON || ret == 1)
> + /*
> + * -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.
> + *
> + * 1 means it's a filter page, no need to deal with.
> + */
The new return code 1 seems to be handled in the same manner as -EHWPOISON,
so how about simply using -EHWPOISON as return code for the new case?
Then, the meaning of -EHWPOISON at this context would change like below:
/*
- * -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.
*/
Thanks,
Naoya Horiguchi
> return;
>
> pr_err("Memory error not recovered");
> @@ -1320,7 +1320,7 @@ 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..1a0bd91a685b 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 1;
> + else
> + return 0;
> }
> unlock_page(head);
> res = MF_FAILED;
> @@ -1545,6 +1548,17 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
> lock_page(head);
> page_flags = head->flags;
>
> + if (hwpoison_filter(p)) {
> + if (TestClearPageHWPoison(head))
> + num_poisoned_pages_dec();
> + put_page(p);
> + if (flags & MF_MCE_HANDLE)
> + res = 1;
> + else
> + res = 0;
> + goto out;
> + }
> +
> /*
> * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
> * simply disable it. In order to make it work properly, we need
> @@ -1613,7 +1627,10 @@ 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 = 1;
> + else
> + rc = 0;
> goto unlock;
> }
>
> @@ -1837,6 +1854,10 @@ int memory_failure(unsigned long pfn, int flags)
> num_poisoned_pages_dec();
> unlock_page(p);
> put_page(p);
> + if (flags & MF_MCE_HANDLE)
> + res = 1;
> + else
> + res = 0;
> goto unlock_mutex;
> }
>
> --
> 2.27.0
