rmap_add() and rmap_recycle() both run in the context of the vCPU and
thus we can use kvm_vcpu_gfn_to_memslot() to look up the memslot. This
enables rmap_add() and rmap_recycle() to take advantage of
vcpu->last_used_slot and avoid expensive memslot searching.
This change improves the performance of "Populate memory time" in
dirty_log_perf_test with tdp_mmu=N. In addition to improving the
performance, "Populate memory time" no longer scales with the number
of memslots in the VM.
Command | Before | After
------------------------------- | ---------------- | -------------
./dirty_log_perf_test -v64 -x1 | 15.18001570s | 14.99469366s
./dirty_log_perf_test -v64 -x64 | 18.71336392s | 14.98675076s
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 35 ++++++++++++++++++++---------------
1 file changed, 20 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a8cdfd8d45c4..370a6ebc2ede 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1043,17 +1043,6 @@ static struct kvm_rmap_head *__gfn_to_rmap(gfn_t gfn, int level,
return &slot->arch.rmap[level - PG_LEVEL_4K][idx];
}
-static struct kvm_rmap_head *gfn_to_rmap(struct kvm *kvm, gfn_t gfn,
- struct kvm_mmu_page *sp)
-{
- struct kvm_memslots *slots;
- struct kvm_memory_slot *slot;
-
- slots = kvm_memslots_for_spte_role(kvm, sp->role);
- slot = __gfn_to_memslot(slots, gfn);
- return __gfn_to_rmap(gfn, sp->role.level, slot);
-}
-
static bool rmap_can_add(struct kvm_vcpu *vcpu)
{
struct kvm_mmu_memory_cache *mc;
@@ -1064,24 +1053,39 @@ static bool rmap_can_add(struct kvm_vcpu *vcpu)
static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
{
+ struct kvm_memory_slot *slot;
struct kvm_mmu_page *sp;
struct kvm_rmap_head *rmap_head;
sp = sptep_to_sp(spte);
kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn);
- rmap_head = gfn_to_rmap(vcpu->kvm, gfn, sp);
+ slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
+ rmap_head = __gfn_to_rmap(gfn, sp->role.level, slot);
return pte_list_add(vcpu, spte, rmap_head);
}
+
static void rmap_remove(struct kvm *kvm, u64 *spte)
{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *slot;
struct kvm_mmu_page *sp;
gfn_t gfn;
struct kvm_rmap_head *rmap_head;
sp = sptep_to_sp(spte);
gfn = kvm_mmu_page_get_gfn(sp, spte - sp->spt);
- rmap_head = gfn_to_rmap(kvm, gfn, sp);
+
+ /*
+ * Unlike rmap_add and rmap_recycle, rmap_remove does not run in the
+ * context of a vCPU so have to determine which memslots to use based
+ * on context information in sp->role.
+ */
+ slots = kvm_memslots_for_spte_role(kvm, sp->role);
+
+ slot = __gfn_to_memslot(slots, gfn);
+ rmap_head = __gfn_to_rmap(gfn, sp->role.level, slot);
+
__pte_list_remove(spte, rmap_head);
}
@@ -1628,12 +1632,13 @@ static bool kvm_test_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
{
+ struct kvm_memory_slot *slot;
struct kvm_rmap_head *rmap_head;
struct kvm_mmu_page *sp;
sp = sptep_to_sp(spte);
-
- rmap_head = gfn_to_rmap(vcpu->kvm, gfn, sp);
+ slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
+ rmap_head = __gfn_to_rmap(gfn, sp->role.level, slot);
kvm_unmap_rmapp(vcpu->kvm, rmap_head, NULL, gfn, sp->role.level, __pte(0));
kvm_flush_remote_tlbs_with_address(vcpu->kvm, sp->gfn,
--
2.32.0.554.ge1b32706d8-goog
