Benjamin Herrenschmidt <b...@kernel.crashing.org> writes: > On Fri, 2016-09-09 at 10:15 +0530, Nikunj A Dadhania wrote: >> > Benjamin Herrenschmidt <b...@kernel.crashing.org> writes: >> >> > >> > On Fri, 2016-09-09 at 09:53 +0530, Nikunj A Dadhania wrote: >> > > >> > > tlbie (and H_REMOVE for pseries) should have a global effect. This is >> > > achieved by iterating and setting tlb_need_flush in all the CPUs. >> > > >> > > > > > Suggested-by: Benjamin Herrenschmidt <b...@kernel.crashing.org> >> > > > > > Signed-off-by: Nikunj A Dadhania <nik...@linux.vnet.ibm.com> >> > > >> > > -- >> > > >> > > Note: Haven't changed following POWERPC_MMU_32B and POWERPC_MMU_601 >> > > yet. >> > > As I am not sure about it. >> > >> > 604 and 7400 can do SMP. >> >> Sure, will add similar logic there. >> >> > >> > That said, I think the approach in your patch is going to be a bit big >> > of a hammer. >> >> > >> > We should have a separate flag indicating that we need to >> > broadcast a flush and only set it on tlbie (non-l) and tlbivax (on >> > BookE) so that we don't end up doing expensive broadcasts on things >> > like context switches. >> >> I had implemented that initially, and was checking that in >> check_tlb_flush, the logic was getting complicated, so thought about >> this way. >> >> Moreover, I was thinking about it, that needs to be a global tcg flag >> and not part the CPUPPCState structure, I was then worried about how to >> synchronise a global tcg variable. > > No it doesn't. > > When a "broadcast TLB" op happens, such as tlbie, you set both flags. > The existing one which just means the current CPU needs flushing, that > logic doesnt' change at all. > > The other one means that *this* CPU needs to broadcast a TLB inval, > thus it's also a local flag ! > > Then you change gen_check_tlb_flush() to take an argument (an immediate > value) which you set to 1 in ptesync on BookS and tlbsync on BookE and > leave 0 on all the others.
One more question, when in gen_check_tlb_flush, don't I need to see if other CPU has global flag set ? Regards, Nikunj
