On 09/22/2015 06:39 PM, Jan Beulich wrote: >>>> On 22.09.15 at 17:28, <rcojoc...@bitdefender.com> wrote: >> On 09/22/2015 06:17 PM, Jan Beulich wrote: >>>>>> On 21.09.15 at 15:31, <rcojoc...@bitdefender.com> wrote: >>>> --- a/xen/arch/x86/hvm/emulate.c >>>> +++ b/xen/arch/x86/hvm/emulate.c >>>> @@ -514,7 +514,8 @@ static int hvmemul_virtual_to_linear( >>>> * being triggered for repeated writes to a whole page. >>>> */ >>>> *reps = min_t(unsigned long, *reps, >>>> - >>>> unlikely(current->domain->arch.mem_access_emulate_enabled) >>>> + >>>> unlikely(current->domain->arch.mem_access_emulate_enabled && >>>> + >>>> current->domain->arch.mem_access_emulate_each_rep) >>>> ? 1 : 4096); >>> >>> unlikely() should not wrap compound conditions, or else its effect of >>> eliminating mis-predicted branches from the fast path won't be >>> achieved. In the case here I wonder though whether you couldn't >>> simply test only ->arch.mem_access_emulate_each_rep. >> >> I'll unfold the unlikely(). >> >> Testing only ->arch.mem_access_emulate_each_rep is what I had done in >> the original patch, however on Andrew Cooper's suggestion I've now gated >> this on ->domain->arch.mem_access_emulate_enabled as well. >> >> Otherwise, somebody might set mem_access_emulate_each_rep via its >> xc_monitor_*() call, but then after calling xc_monitor_disable() it >> would still be in effect, even if the guest is no longer being monitored. >> >> If this is not a problem, I'm happy to check just >> ->arch.mem_access_emulate_each_rep. > > Or perhaps "disabled" should just clear that flag, also to not surprise > the next one to "enable"?
Fair point, I'll do that. Thanks, Razvan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
