From 5dc99b2380d59b8aeafa98791f92b96400ed3187 Mon Sep 17 00:00:00 2001 From: Takuya Yoshikawa Date: Thu, 1 Mar 2012 19:32:16 +0900 Subject: [PATCH] KVM: Avoid checking huge page mappings in get_dirty_log() Dropped such mappings when we enabled dirty logging and we will never create new ones until we stop the logging. For this we introduce a new function which can be used to write protect a range of PT level pages: although we do not need to care about a range of pages at this point, the following patch will need this feature to optimize the write protection of many pages. Signed-off-by: Takuya Yoshikawa Signed-off-by: Avi Kivity --- arch/x86/include/asm/kvm_host.h | 5 +++-- arch/x86/kvm/mmu.c | 40 ++++++++++++++++++++++++--------- arch/x86/kvm/x86.c | 8 +++---- 3 files changed, 36 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index e216ba066e7..f624ca72ea2 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -712,8 +712,9 @@ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask, int kvm_mmu_reset_context(struct kvm_vcpu *vcpu); void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot); -int kvm_mmu_rmap_write_protect(struct kvm *kvm, u64 gfn, - struct kvm_memory_slot *slot); +void kvm_mmu_write_protect_pt_masked(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn_offset, unsigned long mask); void kvm_mmu_zap_all(struct kvm *kvm); unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm); void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages); diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index c8b5694d1a4..dc5f2459db6 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1037,27 +1037,47 @@ static int __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp, int level return write_protected; } -int kvm_mmu_rmap_write_protect(struct kvm *kvm, u64 gfn, - struct kvm_memory_slot *slot) +/** + * kvm_mmu_write_protect_pt_masked - write protect selected PT level pages + * @kvm: kvm instance + * @slot: slot to protect + * @gfn_offset: start of the BITS_PER_LONG pages we care about + * @mask: indicates which pages we should protect + * + * Used when we do not need to care about huge page mappings: e.g. during dirty + * logging we do not have any such mappings. + */ +void kvm_mmu_write_protect_pt_masked(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn_offset, unsigned long mask) { unsigned long *rmapp; - int i, write_protected = 0; - for (i = PT_PAGE_TABLE_LEVEL; - i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) { - rmapp = __gfn_to_rmap(gfn, i, slot); - write_protected |= __rmap_write_protect(kvm, rmapp, i); - } + while (mask) { + rmapp = &slot->rmap[gfn_offset + __ffs(mask)]; + __rmap_write_protect(kvm, rmapp, PT_PAGE_TABLE_LEVEL); - return write_protected; + /* clear the first set bit */ + mask &= mask - 1; + } } static int rmap_write_protect(struct kvm *kvm, u64 gfn) { struct kvm_memory_slot *slot; + unsigned long *rmapp; + int i; + int write_protected = 0; slot = gfn_to_memslot(kvm, gfn); - return kvm_mmu_rmap_write_protect(kvm, gfn, slot); + + for (i = PT_PAGE_TABLE_LEVEL; + i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) { + rmapp = __gfn_to_rmap(gfn, i, slot); + write_protected |= __rmap_write_protect(kvm, rmapp, i); + } + + return write_protected; } static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp, diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 99b738028fc..813ebf1e55a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3095,13 +3095,11 @@ static void write_protect_slot(struct kvm *kvm, /* Not many dirty pages compared to # of shadow pages. */ if (nr_dirty_pages < kvm->arch.n_used_mmu_pages) { - unsigned long gfn_offset; + gfn_t offset; - for_each_set_bit(gfn_offset, dirty_bitmap, memslot->npages) { - unsigned long gfn = memslot->base_gfn + gfn_offset; + for_each_set_bit(offset, dirty_bitmap, memslot->npages) + kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, 1); - kvm_mmu_rmap_write_protect(kvm, gfn, memslot); - } kvm_flush_remote_tlbs(kvm); } else kvm_mmu_slot_remove_write_access(kvm, memslot->id); -- 2.46.0