[PATCH v2] x86/mce: set MCE_IN_KERNEL_COPYIN for all MC-Safe Copy

* [PATCH v2] x86/mce: set MCE_IN_KERNEL_COPYIN for all MC-Safe Copy
@ 2023-05-26  6:32 Kefeng Wang
  2023-05-26  7:09 ` Borislav Petkov
  0 siblings, 1 reply; 7+ messages in thread
From: Kefeng Wang @ 2023-05-26  6:32 UTC (permalink / raw)
  To: tony.luck, bp, naoya.horiguchi, tglx, mingo, dave.hansen, x86,
	akpm, linux-edac, linux-kernel, linux-mm
  Cc: jane.chu, Kefeng Wang

Both EX_TYPE_FAULT_MCE_SAFE and EX_TYPE_DEFAULT_MCE_SAFE exception
fixup types are used to identify fixups which allow in kernel #MC
recovery, that is the Machine Check Safe Copy.

If an MCE which has happened in kernel space but from which the kernel
can recover, mce.kflags MCE_IN_KERNEL_RECOV will set in error_context(),
and we try to fixup the exception in do_machine_check(). But due to lack
of MCE_IN_KERNEL_COPYIN, although the kernel won't panic, the corrupted
page don't be isolated, new one maybe consume it again, which is not what
we expected.

In order to avoid above issue, some hwpoison recover process[1][2][3],
memory_failure_queue() is called to cope with such unhandled corrupted
pages, and recently coredump hwpoison recovery support[4] is asked to
do the same thing, also there are some other already existed MC-safe
copy scenarios, eg, nvdimm, dm-writecache, dax, which don't isolate
corrupted pages.

The best way to fix them is set MCE_IN_KERNEL_COPYIN for MC-Safe Copy,
then let the core do_machine_check() to isolate corrupted page instead
of doing it one-by-one.

[1] commit d302c2398ba2 ("mm, hwpoison: when copy-on-write hits poison, take page offline")
[2] commit 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage copy-on-write faults")
[3] commit 6b970599e807 ("mm: hwpoison: support recovery from ksm_might_need_to_copy()")
[4] https://lkml.kernel.org/r/20230417045323.11054-1-wangkefeng.wang@huawei.com

Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
v2:
- try to describe more clear problem statement, per Dave Hansen
- collect RB

 arch/x86/kernel/cpu/mce/severity.c |  3 +--
 mm/ksm.c                           |  1 -
 mm/memory.c                        | 12 +++---------
 3 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c
index c4477162c07d..63e94484c5d6 100644
--- a/arch/x86/kernel/cpu/mce/severity.c
+++ b/arch/x86/kernel/cpu/mce/severity.c
@@ -293,12 +293,11 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs)
 	case EX_TYPE_COPY:
 		if (!copy_user)
 			return IN_KERNEL;
-		m->kflags |= MCE_IN_KERNEL_COPYIN;
 		fallthrough;
 
 	case EX_TYPE_FAULT_MCE_SAFE:
 	case EX_TYPE_DEFAULT_MCE_SAFE:
-		m->kflags |= MCE_IN_KERNEL_RECOV;
+		m->kflags |= MCE_IN_KERNEL_RECOV | MCE_IN_KERNEL_COPYIN;
 		return IN_KERNEL_RECOV;
 
 	default:
diff --git a/mm/ksm.c b/mm/ksm.c
index 0156bded3a66..7abdf4892387 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2794,7 +2794,6 @@ struct page *ksm_might_need_to_copy(struct page *page,
 	if (new_page) {
 		if (copy_mc_user_highpage(new_page, page, address, vma)) {
 			put_page(new_page);
-			memory_failure_queue(page_to_pfn(page), 0);
 			return ERR_PTR(-EHWPOISON);
 		}
 		SetPageDirty(new_page);
diff --git a/mm/memory.c b/mm/memory.c
index 8358f3b853f2..74873e7126aa 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2813,10 +2813,8 @@ static inline int __wp_page_copy_user(struct page *dst, struct page *src,
 	unsigned long addr = vmf->address;
 
 	if (likely(src)) {
-		if (copy_mc_user_highpage(dst, src, addr, vma)) {
-			memory_failure_queue(page_to_pfn(src), 0);
+		if (copy_mc_user_highpage(dst, src, addr, vma))
 			return -EHWPOISON;
-		}
 		return 0;
 	}
 
@@ -5851,10 +5849,8 @@ static int copy_user_gigantic_page(struct folio *dst, struct folio *src,
 
 		cond_resched();
 		if (copy_mc_user_highpage(dst_page, src_page,
-					  addr + i*PAGE_SIZE, vma)) {
-			memory_failure_queue(page_to_pfn(src_page), 0);
+					  addr + i*PAGE_SIZE, vma))
 			return -EHWPOISON;
-		}
 	}
 	return 0;
 }
@@ -5870,10 +5866,8 @@ static int copy_subpage(unsigned long addr, int idx, void *arg)
 	struct copy_subpage_arg *copy_arg = arg;
 
 	if (copy_mc_user_highpage(copy_arg->dst + idx, copy_arg->src + idx,
-				  addr, copy_arg->vma)) {
-		memory_failure_queue(page_to_pfn(copy_arg->src + idx), 0);
+				  addr, copy_arg->vma))
 		return -EHWPOISON;
-	}
 	return 0;
 }
 
-- 
2.35.3


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