On 2023/5/26 15:09, Borislav Petkov wrote:
On Fri, May 26, 2023 at 02:32:42PM +0800, Kefeng Wang wrote:
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.
No, this whole thing is confused.
* Indicates an MCE that happened in kernel space while copying data
* from user.
#define MCE_IN_KERNEL_COPYIN
This is a very specific exception type: EX_TYPE_COPY which got added by
278b917f8cb9 ("x86/mce: Add _ASM_EXTABLE_CPY for copy user access")
but Linus then removed all such user copy exception points in
034ff37d3407 ("x86: rewrite '__copy_user_nocache' function")
So now that EX_TYPE_COPY never happens.
Is this broken the recover when kernel was copying from user space?
+ Youquan could you help to check it?
And what you're doing is lumping the handling for
EX_TYPE_DEFAULT_MCE_SAFE and EX_TYPE_FAULT_MCE_SAFE together and saying
that the MCE happened while copying data from user.
And XSTATE_OP() is one example where this is not really the case.
Oh, for XSTATE_OP(), it uses EX_TYPE_DEFAULT_MCE_SAFE, but I'm focus on
EX_TYPE_DEFAULT_MCE_SAFE, which use copy_mc (arch/x86/lib/copy_mc_64.S),
like I maintained in changelog, CoW/Coredump/nvdimm/dax, they use
copy_mc_xxx function, sorry for mixed them up.
So no, this is not correct.
so only add MCE_IN_KERNEL_COPYIN for EX_TYPE_DEFAULT_MCE_SAFE?
diff --git a/arch/x86/kernel/cpu/mce/severity.c
b/arch/x86/kernel/cpu/mce/severity.c
index c4477162c07d..6d2587994623 100644
--- a/arch/x86/kernel/cpu/mce/severity.c
+++ b/arch/x86/kernel/cpu/mce/severity.c
@@ -293,11 +293,11 @@ static noinstr int error_context(struct mce *m,
struct pt_regs *regs)
case EX_TYPE_COPY:
if (!copy_user)
return IN_KERNEL;
+ fallthrough;
+ case EX_TYPE_DEFAULT_MCE_SAFE:
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;
return IN_KERNEL_RECOV;
Correct me if I am wrong, thanks for you reviewing.
