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. 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
