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 <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e216ba0..f624ca7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -712,8 +712,9 @@
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 c8b5694..dc5f245 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1037,11 +1037,39 @@
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;
+
+ while (mask) {
+ rmapp = &slot->rmap[gfn_offset + __ffs(mask)];
+ __rmap_write_protect(kvm, rmapp, PT_PAGE_TABLE_LEVEL);
+
+ /* 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);
for (i = PT_PAGE_TABLE_LEVEL;
i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
@@ -1052,14 +1080,6 @@
return write_protected;
}
-static int rmap_write_protect(struct kvm *kvm, u64 gfn)
-{
- struct kvm_memory_slot *slot;
-
- slot = gfn_to_memslot(kvm, gfn);
- return kvm_mmu_rmap_write_protect(kvm, gfn, slot);
-}
-
static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long data)
{
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 99b7380..813ebf1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3095,13 +3095,11 @@
/* 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);