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

Aili Yao
2021-03-12T05:56:21Z

On Thu, 11 Mar 2021 17:05:53 +0000
"Luck, Tony" <tony.luck@intel.com> wrote:

> > I guess that p->mce_vaddr stores the virtual address of the error here.
> > If so, sending SIGBUS with the address looks enough as we do now, so why
> > do you walk page table to find the error virtual address?
>
> p->mce_vaddr only has the virtual address for the COPYIN case. In that code
> path we decode the kernel instruction that hit the fault in order to find the virtual
> address. That's easy because:
>
> 1) The kernel RIP is known to be good (can't page fault etc. on kernel address).
> 2) There are only a half dozen instructions used by the kernel for get_user() or
> copy_from_user().
>
> When the machine check happens during user execution accessing poison data
> we only have the physical address (from MCi_ADDR).
>
> -Tony

Sorry to interrupt as I am really confused here:
If it's a copyin case, has the page been mapped for the current process?
will memory_failure() find it and unmap it? if succeed, then the current will be
signaled with correct vaddr and shift?

Maybe the mce_vaddr is set correctly, but we may lost the correct page shift?

And for copyin case, we don't need to call set_mce_nospec()?

--
Thanks!
Aili Yao