On Wed, 16 Aug 2017 10:18:03 -0700 "Luck, Tony" <[email protected]> wrote:
> Speculative processor accesses may reference any memory that has a > valid page table entry. While a speculative access won't generate > a machine check, it will log the error in a machine check bank. That > could cause escalation of a subsequent error since the overflow bit > will be then set in the machine check bank status register. > > Code has to be double-plus-tricky to avoid mentioning the 1:1 virtual > address of the page we want to map out otherwise we may trigger the > very problem we are trying to avoid. We use a non-canonical address > that passes through the usual Linux table walking code to get to the > same "pte". > > Thanks to Dave Hansen for reviewing several iterations of this. It's unclear (to lil ole me) what the end-user-visible effects of this are. Could we please have a description of that? So a) people can understand your decision to cc:stable and b) people whose kernels are misbehaving can use your description to decide whether your patch might fix the issue their users are reporting. Thanks.
