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

[Luck, Tony]

> 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