[PATCH v3 29/31] KVM: x86/mmu: Avoid memslot lookup in rmap_add

From: Paolo Bonzini
Date: Fri Sep 24 2021 - 12:33:30 EST


From: David Matlack <dmatlack@xxxxxxxxxx>

Avoid the memslot lookup in rmap_add, by passing it down from the fault
handling code to mmu_set_spte and then to rmap_add.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
Message-Id: <20210813203504.2742757-6-dmatlack@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 27 +++++++--------------------
arch/x86/kvm/mmu/paging_tmpl.h | 12 +++++++++---
2 files changed, 16 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4b304f60cf44..7ff2c6c896a8 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1625,16 +1625,15 @@ static bool kvm_test_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,

#define RMAP_RECYCLE_THRESHOLD 1000

-static void rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
+static void rmap_add(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,
+ u64 *spte, gfn_t gfn)
{
- struct kvm_memory_slot *slot;
struct kvm_mmu_page *sp;
struct kvm_rmap_head *rmap_head;
int rmap_count;

sp = sptep_to_sp(spte);
kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn);
- slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
rmap_head = gfn_to_rmap(gfn, sp->role.level, slot);
rmap_count = pte_list_add(vcpu, spte, rmap_head);

@@ -2674,8 +2673,8 @@ int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync,
return 0;
}

-static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
- unsigned int pte_access, gfn_t gfn,
+static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,
+ u64 *sptep, unsigned int pte_access, gfn_t gfn,
kvm_pfn_t pfn, struct kvm_page_fault *fault)
{
struct kvm_mmu_page *sp = sptep_to_sp(sptep);
@@ -2744,24 +2743,12 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
if (!was_rmapped) {
WARN_ON_ONCE(ret == RET_PF_SPURIOUS);
kvm_update_page_stats(vcpu->kvm, level, 1);
- rmap_add(vcpu, sptep, gfn);
+ rmap_add(vcpu, slot, sptep, gfn);
}

return ret;
}

-static kvm_pfn_t pte_prefetch_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn,
- bool no_dirty_log)
-{
- struct kvm_memory_slot *slot;
-
- slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, no_dirty_log);
- if (!slot)
- return KVM_PFN_ERR_FAULT;
-
- return gfn_to_pfn_memslot_atomic(slot, gfn);
-}
-
static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp,
u64 *start, u64 *end)
@@ -2782,7 +2769,7 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
return -1;

for (i = 0; i < ret; i++, gfn++, start++) {
- mmu_set_spte(vcpu, start, access, gfn,
+ mmu_set_spte(vcpu, slot, start, access, gfn,
page_to_pfn(pages[i]), NULL);
put_page(pages[i]);
}
@@ -2984,7 +2971,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
if (WARN_ON_ONCE(it.level != fault->goal_level))
return -EFAULT;

- ret = mmu_set_spte(vcpu, it.sptep, ACC_ALL,
+ ret = mmu_set_spte(vcpu, fault->slot, it.sptep, ACC_ALL,
base_gfn, fault->pfn, fault);
if (ret == RET_PF_SPURIOUS)
return ret;
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 8c07c42a4d73..44361f7e70c8 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -561,6 +561,7 @@ static bool
FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
u64 *spte, pt_element_t gpte, bool no_dirty_log)
{
+ struct kvm_memory_slot *slot;
unsigned pte_access;
gfn_t gfn;
kvm_pfn_t pfn;
@@ -573,12 +574,17 @@ FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
gfn = gpte_to_gfn(gpte);
pte_access = sp->role.access & FNAME(gpte_access)(gpte);
FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte);
- pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn,
+
+ slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn,
no_dirty_log && (pte_access & ACC_WRITE_MASK));
+ if (!slot)
+ return false;
+
+ pfn = gfn_to_pfn_memslot_atomic(slot, gfn);
if (is_error_pfn(pfn))
return false;

- mmu_set_spte(vcpu, spte, pte_access, gfn, pfn, NULL);
+ mmu_set_spte(vcpu, slot, spte, pte_access, gfn, pfn, NULL);
kvm_release_pfn_clean(pfn);
return true;
}
@@ -757,7 +763,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
if (WARN_ON_ONCE(it.level != fault->goal_level))
return -EFAULT;

- ret = mmu_set_spte(vcpu, it.sptep, gw->pte_access,
+ ret = mmu_set_spte(vcpu, fault->slot, it.sptep, gw->pte_access,
base_gfn, fault->pfn, fault);
if (ret == RET_PF_SPURIOUS)
return ret;
--
2.27.0