> -----Original Message----- > From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx] > Sent: Tuesday, October 09, 2012 9:56 PM > To: Christoffer Dall > Cc: Min-gyu Kim; 김창환; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx; kvmarm@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: [kvmarm] [PATCH v2 06/14] KVM: ARM: Memory virtualization > setup > > On Sat, 6 Oct 2012 17:33:43 -0400, Christoffer Dall > <c.dall@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Oct 4, 2012 at 10:23 PM, Min-gyu Kim > > <mingyu84.kim@xxxxxxxxxxx> > > wrote: > >> > >> > >>> -----Original Message----- > >>> From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] > >>> On Behalf Of Christoffer Dall > >>> Sent: Monday, October 01, 2012 6:11 PM > >>> To: kvm@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > >>> kvmarm@xxxxxxxxxxxxxxxxxxxxx > >>> Cc: Marc Zyngier > >>> Subject: [PATCH v2 06/14] KVM: ARM: Memory virtualization setup > >>> > >>> +static void stage2_set_pte(struct kvm *kvm, struct > kvm_mmu_memory_cache > >>> *cache, > >>> + phys_addr_t addr, const pte_t *new_pte) { > >>> + pgd_t *pgd; > >>> + pud_t *pud; > >>> + pmd_t *pmd; > >>> + pte_t *pte, old_pte; > >>> + > >>> + /* Create 2nd stage page table mapping - Level 1 */ > >>> + pgd = kvm->arch.pgd + pgd_index(addr); > >>> + pud = pud_offset(pgd, addr); > >>> + if (pud_none(*pud)) { > >>> + if (!cache) > >>> + return; /* ignore calls from kvm_set_spte_hva */ > >>> + pmd = mmu_memory_cache_alloc(cache); > >>> + pud_populate(NULL, pud, pmd); > >>> + pmd += pmd_index(addr); > >>> + get_page(virt_to_page(pud)); > >>> + } else > >>> + pmd = pmd_offset(pud, addr); > >>> + > >>> + /* Create 2nd stage page table mapping - Level 2 */ > >>> + if (pmd_none(*pmd)) { > >>> + if (!cache) > >>> + return; /* ignore calls from kvm_set_spte_hva */ > >>> + pte = mmu_memory_cache_alloc(cache); > >>> + clean_pte_table(pte); > >>> + pmd_populate_kernel(NULL, pmd, pte); > >>> + pte += pte_index(addr); > >>> + get_page(virt_to_page(pmd)); > >>> + } else > >>> + pte = pte_offset_kernel(pmd, addr); > >>> + > >>> + /* Create 2nd stage page table mapping - Level 3 */ > >>> + old_pte = *pte; > >>> + set_pte_ext(pte, *new_pte, 0); > >>> + if (pte_present(old_pte)) > >>> + __kvm_tlb_flush_vmid(kvm); > >>> + else > >>> + get_page(virt_to_page(pte)); } > >> > >> > >> I'm not sure about the 3-level page table, but isn't it necessary to > >> clean the page table for 2nd level? > >> There are two mmu_memory_cache_alloc calls. One has following > >> clean_pte_table and the other doesn't have. > > > > hmm, it probably is - I couldn't really find the common case where > > this is done in the kernel normally (except for some custom loop in > > ioremap and idmap), but I added this fix: > > > > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index > > 5394a52..f11ba27f 100644 > > --- a/arch/arm/kvm/mmu.c > > +++ b/arch/arm/kvm/mmu.c > > @@ -430,6 +430,7 @@ static void stage2_set_pte(struct kvm *kvm, struct > > kvm_mmu_memory_cache *cache, > > if (!cache) > > return; /* ignore calls from kvm_set_spte_hva */ > > pmd = mmu_memory_cache_alloc(cache); > > + clean_dcache_area(pmd, PTRS_PER_PMD * sizeof(pmd_t)); > > pud_populate(NULL, pud, pmd); > > pmd += pmd_index(addr); > > get_page(virt_to_page(pud)); > > There ought to be a test of ID_MMFR3[23:20] to find out whether or not it > is useful to clean the dcache. Not sure if that's a massive gain, but it > is certainly an optimisation to consider for the kernel as a whole. That's part of what I was wondering. clean_dcache_area is substituted by nop if TLB_CAN_READ_FROM_L1_CACHE is defined(mm/proc-v7.S). But I couldn't find any place where it is defined. If it is part of bsp to enable TLB_CAN_RAD_FROM_L1_CACHE according to ID_MMFR3[23:20], it would not be necessary to concerned about cleaning or not cleaning. However, am I right? > > M. > -- > Fast, cheap, reliable. Pick two. -- 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
