On Thu, Aug 30, 2018 at 6:49 PM Tony Luck <tony.l...@intel.com> wrote: > > Just checking "do we have a non-canonical address" at the bottom of that > call stack and flipping bit 63 back on again seems like a bad idea.
You could literally do something like /* Make it canonical in case we flipped the high bit */ addr = (long)(addr<<1)>>1; in the call to clflush and it magically does the right thing. Pretty? No. But with a big comment about what is going on and why it's done, I think it's prettier than your much bigger patch. I dunno. It does strike me as a bit hacky, but I'd rather have a *small* one-liner hack that generates two instructions, than add a complex hack that modifies the page tables three times and has a serializing instruction in it. Both are subtle fixes for a subtle issue, but one seems pretty harmless in comparison. Hmm? But I'll bow to the x86 maintainers. Linus