On 20.12.2019 15:51, Andrew Cooper wrote: > On 20/12/2019 14:20, Jan Beulich wrote: >> get_page_light()'s use of cmpxchg() is a full barrier already anyway. >> >> Signed-off-by: Jan Beulich <jbeul...@suse.com> > > While true, is this actually a clever change to make? > > The implementation of get_page_light() could plausibly change and no > longer be a full barrier, introducing a vulnerability here. OTOH, > smp_wmb() is free.
It's free at the CPU level, but not at the compiler one (where it still is a barrier). I also don't think get_page_light() could change as drastically as losing its LOCK-ed operation, or if it did the author (and reviewer) would be well advised to at least briefly audit use sites (one of the reasons I'm leaving a comment). Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
