On Mon, Jun 4, 2018 at 10:08 AM, Luck, Tony <tony.luck@xxxxxxxxx> wrote:
> On Sat, Jun 02, 2018 at 10:23:20PM -0700, Dan Williams wrote:
>> +static inline int set_mce_nospec(unsigned long pfn)
>> +{
>> + int rc;
>> +
>> + rc = set_memory_uc((unsigned long) __va(PFN_PHYS(pfn)), 1);
>
> You should really do the decoy_addr thing here that I had in mce_unmap_kpfn().
> Putting the virtual address of the page you mustn't accidentally prefetch
> from into a register is a pretty good way to make sure that the processor
> does do a prefetch.
Maybe I'm misreading, but doesn't that make the page completely
inaccessible? We still want to read pmem through the driver and the
linear mapping with memcpy_mcsafe(). Alternatively I could just drop
this patch and setup a private / alias mapping for the pmem driver to
use. It seems aliased mappings would be the safer option, but I want
to make sure I've comprehended your suggestion correctly?
