On Thu, May 02, 2013 at 04:15:05PM +0100, Christoffer Dall wrote: > On Thu, May 2, 2013 at 8:03 AM, Will Deacon <will.deacon@xxxxxxx> wrote: > > On Thu, May 02, 2013 at 03:39:00PM +0100, Marc Zyngier wrote: > >> Patch 5a677ce044f1 (ARM: KVM: switch to a dual-step HYP init code) > >> introduced code that flushes page tables to the point of coherency. > >> This is overkill (point of unification is enough and already done), > >> and actually not required if running on a SMP capable platform > >> (the HW PTW can snoop other cpus' L1). > >> > >> Remove this code and let ae8a8b9553bd (ARM: 7691/1: mm: kill unused > >> TLB_CAN_READ_FROM_L1_CACHE and use ALT_SMP instead) turn it into > >> a no-op for SMP ARMv7. > >> > >> Reported-by: Catalin Marinas <catalin.marinas@xxxxxxx> > >> Cc: Will Deacon <will.deacon@xxxxxxx> > >> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> > >> --- > >> arch/arm/kvm/mmu.c | 3 --- > >> 1 file changed, 3 deletions(-) > >> > >> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > >> index 4a838db..d79b594 100644 > >> --- a/arch/arm/kvm/mmu.c > >> +++ b/arch/arm/kvm/mmu.c > >> @@ -234,7 +234,6 @@ static void create_hyp_pte_mappings(pmd_t *pmd, unsigned long start, > >> pte = pte_offset_kernel(pmd, addr); > >> kvm_set_pte(pte, pfn_pte(pfn, prot)); > >> get_page(virt_to_page(pte)); > >> - kvm_flush_dcache_to_poc(pte, sizeof(*pte)); > >> pfn++; > >> } while (addr += PAGE_SIZE, addr != end); > > > > Could you remove the flushing code out of kvm_set_pte, then flush the range > > after the loop? Then you get one flush and one barrier for the whole range. > > > that would be different from how it's done in the rest of the kernel > where you're expecting set_pte to do the necessary flushing for you, > no? Correct, but since kvm_set_pte seems only to be called from this file, I'm not sure you need to match thes rest of the kernel. > instead, if this optimization is worth it, the code could just use > pte_val(pte) = XX; or just *pte = XX; Will -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
