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    SubjectRe: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

    > >
    > > Returning true means you stop walking when you find the first entry pointing
    > > to a given pfn. But there could be multiple such entries, so if MCE SRAR is
    > > triggered by memory access to the larger address in hwpoisoned entries, the
    > > returned virtual address might be wrong.
    > >
    >
    > I can't find the way to fix this, maybe the virtual address is contained in
    > related register, but this is really beyong my knowledge.
    >
    > This is a v2 RFC patch, add support for thp and 1G huge page errors.
    >

    Sorry for the debug info and other unclean modifications.

    Post a clean one.

    Thanks
    Aili Yao

    From 2289276ba943cdcddbf3b5b2cdbcaff78690e2e8 Mon Sep 17 00:00:00 2001
    From: Aili Yao <yaoaili@kingsoft.com>
    Date: Wed, 17 Mar 2021 16:12:41 +0800
    Subject: [PATCH] fix invalid SIGBUS address for recovery fail

    Walk the current process pages and compare with the pfn, then get the
    user address and related page_shift.

    For thp pages, we can only split anonoums thp page, so I think there may
    be no race condition for walking and searching the thp error page for such
    case; For non anonymous thp, the page flag and pte will not be change. so
    when code goes into this place, it may be race condition for non-anonoums
    thp page or from a recovery fail for anonoums thp, the page status will
    not change, i am not so sure about this;

    For the case we don't find the related virtual address, Maybe sending one
    BUS_MCEERR_AR signal with invalid address NULL is a better option, but i am
    not sure.

    And this may get the wrong virtual address if process have multiple entry
    for a same page, I don't find a way to get it correct.

    Maybe other issues is not recognized.
    ---
    arch/x86/kernel/cpu/mce/core.c | 12 +---
    include/linux/mm.h | 1 +
    mm/memory-failure.c | 127 +++++++++++++++++++++++++++++++++++++++++
    3 files changed, 131 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
    index db4afc5..4cb873c 100644
    --- a/arch/x86/kernel/cpu/mce/core.c
    +++ b/arch/x86/kernel/cpu/mce/core.c
    @@ -1246,7 +1246,7 @@ 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;

    - pr_err("Uncorrected hardware memory error in user-access at %llx", p->mce_addr);
    + pr_err("Uncorrected hardware memory error in user-access at %llx\n", p->mce_addr);

    if (!p->mce_ripv)
    flags |= MF_MUST_KILL;
    @@ -1258,14 +1258,8 @@ static void kill_me_maybe(struct callback_head *cb)
    return;
    }

    - 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");
    - kill_me_now(cb);
    - }
    + memory_failure_error(current, p->mce_addr >> PAGE_SHIFT);
    +
    }

    static void queue_task_work(struct mce *m, int kill_current_task)
    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index ecdf8a8..cff2f02 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -3046,6 +3046,7 @@ enum mf_flags {
    MF_SOFT_OFFLINE = 1 << 3,
    };
    extern int memory_failure(unsigned long pfn, int flags);
    +extern void memory_failure_error(struct task_struct *p, unsigned long pfn);
    extern void memory_failure_queue(unsigned long pfn, int flags);
    extern void memory_failure_queue_kick(int cpu);
    extern int unpoison_memory(unsigned long pfn);
    diff --git a/mm/memory-failure.c b/mm/memory-failure.c
    index 06f0061..359b42f 100644
    --- a/mm/memory-failure.c
    +++ b/mm/memory-failure.c
    @@ -56,6 +56,7 @@
    #include <linux/kfifo.h>
    #include <linux/ratelimit.h>
    #include <linux/page-isolation.h>
    +#include <linux/pagewalk.h>
    #include "internal.h"
    #include "ras/ras_event.h"

    @@ -1553,6 +1554,132 @@ int memory_failure(unsigned long pfn, int flags)
    }
    EXPORT_SYMBOL_GPL(memory_failure);

    +static int pte_range(pte_t *ptep, unsigned long addr, unsigned long next, struct mm_walk *walk)
    +{
    + u64 *buff = (u64 *)walk->private;
    + u64 pfn = buff[0];
    + pte_t pte = *ptep;
    +
    + if (!pte_none(pte) && !pte_present(pte)) {
    + swp_entry_t swp_temp = pte_to_swp_entry(pte);
    +
    + if (is_hwpoison_entry(swp_temp) && swp_offset(swp_temp) == pfn)
    + goto find;
    + } else if (pte_pfn(pte) == pfn) {
    + goto find;
    + }
    +
    + return 0;
    +
    +find:
    + buff[0] = addr;
    + buff[1] = PAGE_SHIFT;
    + return true;
    +}
    +
    +static int pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
    + struct mm_walk *walk)
    +{
    + u64 *buff = (u64 *)walk->private;
    + struct page *page = (struct page *)buff[0];
    + u64 pfn = buff[1];
    + pmd_t pmd = *pmdp;
    +
    + if (likely(!pmd_trans_huge(pmd)))
    + return 0;
    +
    + if (pmd_none(pmd) || !pmd_present(pmd))
    + return 0;
    +
    + if (pmd_page(pmd) != page)
    + return 0;
    +
    + for (; addr != end; page++, addr += PAGE_SIZE) {
    + if (page_to_pfn(page) == pfn) {
    + buff[0] = addr;
    + buff[1] = PAGE_SHIFT;
    + return true;
    + }
    + }
    +
    + return 0;
    +}
    +
    +static int hugetlb_range(pte_t *ptep, unsigned long hmask,
    + unsigned long addr, unsigned long end,
    + struct mm_walk *walk)
    +{
    + u64 *buff = (u64 *)walk->private;
    + u64 pfn = buff[0];
    + pte_t pte = huge_ptep_get(ptep);
    + struct page *page = pfn_to_page(pfn);
    +
    + if (!huge_pte_none(pte) && !pte_present(pte)) {
    + swp_entry_t swp_temp = pte_to_swp_entry(pte);
    +
    + if (is_hwpoison_entry(swp_temp) && swp_offset(swp_temp) == pfn)
    + goto find;
    + }
    + if (pte_pfn(pte) == pfn)
    + goto find;
    +
    + return 0;
    +
    +find:
    + buff[0] = addr;
    + buff[1] = (huge_page_size(page_hstate(page)) > PMD_SIZE) ? PUD_SHIFT : PMD_SHIFT;
    + return true;
    +}
    +
    +void memory_failure_error(struct task_struct *p, unsigned long pfn)
    +{
    + u64 buff[2] = {0};
    + struct page *page;
    + int ret = -1;
    + struct mm_walk_ops walk = {0};
    +
    + if (p->mce_vaddr != (void __user *)-1l && p->mce_vaddr != (void __user *)0) {
    + force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT);
    + return;
    + }
    +
    + page = pfn_to_page(pfn);
    + if (!page)
    + goto force_sigbus;
    +
    + if (is_zone_device_page(page))
    + goto force_sigbus;
    +
    + page = compound_head(page);
    +
    + if (PageHuge(page)) {
    + walk.hugetlb_entry = hugetlb_range;
    + buff[0] = page_to_pfn(page);
    + } else if (PageTransHuge(page)) {
    + walk.pmd_entry = pmd_range;
    + buff[0] = (u64)page;
    + buff[1] = pfn;
    + } else {
    + walk.pte_entry = pte_range;
    + buff[0] = pfn;
    + }
    +
    + mmap_read_lock(p->mm);
    + ret = walk_page_range(p->mm, 0, TASK_SIZE_MAX, &walk, (void *)buff);
    + mmap_read_unlock(p->mm);
    +
    + pr_err("Memory error may not recovered: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
    + pfn, p->comm, p->pid);
    +
    + if (ret) {
    + force_sig_mceerr(BUS_MCEERR_AR, (void __user *)buff[0], buff[1]);
    + } else {
    +force_sigbus:
    + force_sig_mceerr(BUS_MCEERR_AR, (void __user *)0, PAGE_SHIFT);
    + }
    +}
    +EXPORT_SYMBOL_GPL(memory_failure_error);
    +
    #define MEMORY_FAILURE_FIFO_ORDER 4
    #define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER)

    --
    1.8.3.1
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