Voila! Since the map walkers are able to work in parallel there is no
need to take the write lock on a stage 2 memory abort. Relax locking
on map operations and cross fingers we got it right.
Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
---
arch/arm64/kvm/mmu.c | 21 +++------------------
1 file changed, 3 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 63cf18cdb978..2881051c3743 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1127,7 +1127,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
gfn_t gfn;
kvm_pfn_t pfn;
bool logging_active = memslot_is_logging(memslot);
- bool use_read_lock = false;
unsigned long fault_level = kvm_vcpu_trap_get_fault_level(vcpu);
unsigned long vma_pagesize, fault_granule;
enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
@@ -1162,8 +1161,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (logging_active) {
force_pte = true;
vma_shift = PAGE_SHIFT;
- use_read_lock = (fault_status == FSC_PERM && write_fault &&
- fault_granule == PAGE_SIZE);
} else {
vma_shift = get_vma_page_shift(vma, hva);
}
@@ -1267,15 +1264,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (exec_fault && device)
return -ENOEXEC;
- /*
- * To reduce MMU contentions and enhance concurrency during dirty
- * logging dirty logging, only acquire read lock for permission
- * relaxation.
- */
- if (use_read_lock)
- read_lock(&kvm->mmu_lock);
- else
- write_lock(&kvm->mmu_lock);
+ read_lock(&kvm->mmu_lock);
+
pgt = vcpu->arch.hw_mmu->pgt;
if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;
@@ -1322,8 +1312,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (fault_status == FSC_PERM && vma_pagesize == fault_granule) {
ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);
} else {
- WARN_ONCE(use_read_lock, "Attempted stage-2 map outside of write lock\n");
-
ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,
__pfn_to_phys(pfn), prot,
mmu_caches, true);
@@ -1336,10 +1324,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
}
out_unlock:
- if (use_read_lock)
- read_unlock(&kvm->mmu_lock);
- else
- write_unlock(&kvm->mmu_lock);
+ read_unlock(&kvm->mmu_lock);
kvm_set_pfn_accessed(pfn);
kvm_release_pfn_clean(pfn);
return ret != -EAGAIN ? ret : 0;
--
2.36.0.rc0.470.gd361397f0d-goog
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