On Thu, Feb 16, 2017 at 04:02:57PM -0500, Waiman Long wrote: > On 02/16/2017 11:09 AM, Peter Zijlstra wrote: > > On Wed, Feb 15, 2017 at 04:37:49PM -0500, Waiman Long wrote: > >> The cpu argument in the function prototype of vcpu_is_preempted() > >> is changed from int to long. That makes it easier to provide a better > >> optimized assembly version of that function. > >> > >> For Xen, vcpu_is_preempted(long) calls xen_vcpu_stolen(int), the > >> downcast from long to int is not a problem as vCPU number won't exceed > >> 32 bits. > >> > > Note that because of the cast in PVOP_CALL_ARG1() this patch is > > pointless. > > > > Then again, it doesn't seem to affect code generation, so why not. Takes > > away the reliance on that weird cast. > > I add this patch because I am a bit uneasy about clearing the upper 32 > bits of rdi and assuming that the compiler won't have a previous use of > those bits. It gives me peace of mind. So currently the PVOP_CALL_ARG#() macros force cast everything to (unsigned long) anyway, but it would be good not to rely on that I think, so yes.
