[PATCH v4 2/2] mm/memory-failure: disable unpoison once hw error happens

[zhenwei pi]

Currently unpoison_memory(unsigned long pfn) is designed for soft
poison(hwpoison-inject) only. Since 17fae1294ad9d, the KPTE gets
cleared on a x86 platform once hardware memory corrupts.

Unpoisoning a hardware corrupted page puts page back buddy only,
the kernel has a chance to access the page with *NOT PRESENT* KPTE.
This leads BUG during accessing on the corrupted KPTE.

Do not allow to unpoison hardware corrupted page in unpoison_memory() to
avoid BUG like this:

 Unpoison: Software-unpoisoned page 0x61234
 BUG: unable to handle page fault for address: ffff888061234000
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 PGD 2c01067 P4D 2c01067 PUD 107267063 PMD 10382b063 PTE 800fffff9edcb062
 Oops: 0002 [#1] PREEMPT SMP NOPTI
 CPU: 4 PID: 26551 Comm: stress Kdump: loaded Tainted: G   M       OE     5.18.0.bm.1-amd64 #7
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ...
 RIP: 0010:clear_page_erms+0x7/0x10
 Code: ...
 RSP: 0000:ffffc90001107bc8 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: 0000000000000901 RCX: 0000000000001000
 RDX: ffffea0001848d00 RSI: ffffea0001848d40 RDI: ffff888061234000
 RBP: ffffea0001848d00 R08: 0000000000000901 R09: 0000000000001276
 R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000000001
 R13: 0000000000000000 R14: 0000000000140dca R15: 0000000000000001
 FS:  00007fd8b2333740(0000) GS:ffff88813fd00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffff888061234000 CR3: 00000001023d2005 CR4: 0000000000770ee0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 55555554
 Call Trace:
  <TASK>
  prep_new_page+0x151/0x170
  get_page_from_freelist+0xca0/0xe20
  ? sysvec_apic_timer_interrupt+0xab/0xc0
  ? asm_sysvec_apic_timer_interrupt+0x1b/0x20
  __alloc_pages+0x17e/0x340
  __folio_alloc+0x17/0x40
  vma_alloc_folio+0x84/0x280
  __handle_mm_fault+0x8d4/0xeb0
  handle_mm_fault+0xd5/0x2a0
  do_user_addr_fault+0x1d0/0x680
  ? kvm_read_and_reset_apf_flags+0x3b/0x50
  exc_page_fault+0x78/0x170
  asm_exc_page_fault+0x27/0x30

Suggested by David&Naoya, disable unpoison mechanism when a real HW error
happens.

Fixes: 847ce401df392 ("HWPOISON: Add unpoisoning support")
Fixes: 17fae1294ad9d ("x86/{mce,mm}: Unmap the entire page if the whole page is affected and poisoned")
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
---
 Documentation/vm/hwpoison.rst | 3 ++-
 mm/hwpoison-inject.c          | 6 ++++++
 mm/memory-failure.c           | 1 +
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/vm/hwpoison.rst b/Documentation/vm/hwpoison.rst
index c832a8b192d4..ac439381cad4 100644
--- a/Documentation/vm/hwpoison.rst
+++ b/Documentation/vm/hwpoison.rst
@@ -120,7 +120,8 @@ Testing
   unpoison-pfn
 	Software-unpoison page at PFN echoed into this file. This way
 	a page can be reused again.  This only works for Linux
-	injected failures, not for real memory failures.
+	injected failures, not for real memory failures. Once any hardware
+	memory failure happens, the feature is disabled.
 
   Note these injection interfaces are not stable and might change between
   kernel versions
diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
index 9e522ecedeef..787d2daf41e8 100644
--- a/mm/hwpoison-inject.c
+++ b/mm/hwpoison-inject.c
@@ -7,6 +7,7 @@
 #include <linux/swap.h>
 #include <linux/pagemap.h>
 #include <linux/hugetlb.h>
+#include <linux/swapops.h>
 #include "internal.h"
 
 static struct dentry *hwpoison_dir;
@@ -65,6 +66,11 @@ static int hwpoison_unpoison(void *data, u64 val)
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (atomic_read(&hwpoisoned_pages) != atomic_long_read(&num_poisoned_pages)) {
+		pr_info("Unpoison is disabled after hardware memory failure happened\n");
+		return -EOPNOTSUPP;
+	}
+
 	ret = unpoison_memory(val);
 	if (!ret) {
 		atomic_dec(&hwpoisoned_pages);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b85661cbdc4a..a3e6bd4b5528 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -68,6 +68,7 @@ int sysctl_memory_failure_early_kill __read_mostly = 0;
 int sysctl_memory_failure_recovery __read_mostly = 1;
 
 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
+EXPORT_SYMBOL_GPL(num_poisoned_pages);
 
 static bool __page_handle_poison(struct page *page)
 {
-- 
2.20.1