On 6/8/22 17:30, David Hildenbrand wrote:
On 08.06.22 10:43, zhenwei pi wrote:
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
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>
Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
---
mm/memory-failure.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b85661cbdc4a..da99a2b7ef35 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2090,6 +2090,7 @@ int unpoison_memory(unsigned long pfn)
{
struct page *page;
struct page *p;
+ pte_t *kpte;
int ret = -EBUSY;
int freeit = 0;
static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
@@ -2103,6 +2104,14 @@ int unpoison_memory(unsigned long pfn)
mutex_lock(&mf_mutex);
+ kpte = virt_to_kpte((unsigned long)page_to_virt(p));
I'm curious whether virt_to_kpte is sane to use, especially, when having
the direct map map PMDs and not PTEs?
virt_to_kpte() only checks for pmd_none() -- but what if we have
pmd_large()?
Naive me would assume that calling virt_to_kpte() from generic code is
broken. Only mm/highmem.c uses it, however, 32bit most probably also
doesn't have large mappings in the page tables for the direct map.
Hi,
I dived into this part and noticed that both pmd_off_k() and
virt_to_kpte() are broken.
For example, on a x86 platform, if the CPU has feature 'pdpe1gb', the
kernel prefers 1G map. (cat /proc/meminfo | grep DirectMap to show the
current mapping)
static inline pmd_t *pmd_off_k(unsigned long va)
{
return pmd_offset(pud_offset(p4d_offset(pgd_offset_k(va), va),
va), va);
}
There is no pud_none() & pud_large()(of cause, we can't use pud_large()
here) to test *PUD* valid or not.
So I'm going to do:
- in pmd_off_k(), use pud_none() and pud_bad() to test *PUD*, if failed,
BUG().
- in virt_to_kpte(), use pmd_none() & pmd_bad() to test *PMD*, if
failed, BUG().
- rework KPTE test in unpoison_memory(), walk page table instead of
useing virt_to_kpte().
Do you have any suggestions?
--
zhenwei pi
