Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*

Andrew Lutomirski
2014-04-22T01:28:35Z

On Mon, Apr 21, 2014 at 6:14 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> I wanted to avoid the "another cpu made this allocation, now I have to free" crap, but I also didn't want to grab the lock if there was no work needed.

I guess you also want to avoid bouncing all these cachelines around on
boot on bit multicore machines.

I'd advocate using the bitmap approach or simplifying the existing
code. For example:

+ for (n = 0; n < ESPFIX_PUD_CLONES; n++) {
+ pud = ACCESS_ONCE(pud_p[n]);
+ if (!pud_present(pud))
+ return false;
+ }

I don't see why that needs to be a loop. How can one clone exist but
not the others?

--Andy