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

Aili Yao
2021-03-17T07:49:00Z

>
> 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.

Thanks
Aili Yao

From 31b685609610b3b06c8fd98d866913dbfeb7e159 Mon Sep 17 00:00:00 2001
From: Aili Yao <yaoaili@kingsoft.com>
Date: Wed, 17 Mar 2021 15:34:15 +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 | 16 ++---
include/linux/mm.h | 1 +
mm/memory-failure.c | 145 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 152 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index db4afc5..1bf21cc 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -28,8 +28,12 @@
#include <linux/sysfs.h>
#include <linux/types.h>
#include <linux/slab.h>
+#include <linux/hugetlb.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
#include <linux/init.h>
#include <linux/kmod.h>
+#include <linux/pagewalk.h>
#include <linux/poll.h>
#include <linux/nmi.h>
#include <linux/cpu.h>
@@ -1246,7 +1250,7 @@ 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, %llx", p->mce_addr, p->mce_vaddr);

if (!p->mce_ripv)
flags |= MF_MUST_KILL;
@@ -1258,14 +1262,8 @@ 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..aaf99a7 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -56,8 +56,10 @@
#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"
+#include <linux/delay.h>

int sysctl_memory_failure_early_kill __read_mostly = 0;

@@ -240,7 +242,7 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
int ret = 0;

pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
- pfn, t->comm, t->pid);
+ tk->addr, t->comm, t->pid);

if (flags & MF_ACTION_REQUIRED) {
WARN_ON_ONCE(t != current);
@@ -1417,6 +1419,7 @@ int memory_failure(unsigned long pfn, int flags)
try_again:
if (PageHuge(p))
return memory_failure_hugetlb(pfn, flags);
+
if (TestSetPageHWPoison(p)) {
pr_err("Memory failure: %#lx: already hardware poisoned\n",
pfn);
@@ -1553,6 +1556,146 @@ 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);
+
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ if (is_hwpoison_entry(swp_temp) && swp_offset(swp_temp) == pfn) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ goto find;
+ }
+ } else if (pte_pfn(pte) == pfn) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ 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) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ 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);
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ if (is_hwpoison_entry(swp_temp) && swp_offset(swp_temp) == pfn) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ goto find;
+ }
+ }
+ if (pte_pfn(pte) == pfn) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ 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) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ 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)) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ walk.hugetlb_entry = hugetlb_range;
+ buff[0] = page_to_pfn(page);
+ } else if (PageTransHuge(page)) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ walk.pmd_entry = pmd_range;
+ buff[0] = (u64)page;
+ buff[1] = pfn;
+ } else {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ walk.pte_entry = pte_range;
+ buff[0] = pfn;
+ }
+ msleep(1000);
+ 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) {
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ force_sig_mceerr(BUS_MCEERR_AR, (void __user *)buff[0], buff[1]);
+ } else {
+force_sigbus:
+ printk("%s, %d \n", __FUNCTION__, __LINE__);
+ 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