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KVM: arm64: Add fast path to handle permission relaxation during dirty logging

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To reduce MMU lock contention during dirty logging, all permission
relaxation operations would be performed under read lock.

Signed-off-by: Jing Zhang <jingzhangos@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220118015703.3630552-3-jingzhangos@google.com
This commit is contained in:
Jing Zhang 2022-01-18 01:57:02 +00:00 committed by Marc Zyngier
parent fcc5bf8963
commit f783ef1c0e
1 changed files with 15 additions and 2 deletions
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17
arch/arm64/kvm/mmu.c
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@ -1080,6 +1080,7 @@ 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 logging_perm_fault = 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;
@ -1114,6 +1115,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (logging_active) {
force_pte = true;
vma_shift = PAGE_SHIFT;
logging_perm_fault = (fault_status == FSC_PERM && write_fault);
} else {
vma_shift = get_vma_page_shift(vma, hva);
}
@ -1212,7 +1214,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (exec_fault && device)
return -ENOEXEC;
write_lock(&kvm->mmu_lock);
/*
* To reduce MMU contentions and enhance concurrency during dirty
* logging dirty logging, only acquire read lock for permission
* relaxation.
*/
if (logging_perm_fault)
read_lock(&kvm->mmu_lock);
else
write_lock(&kvm->mmu_lock);
pgt = vcpu->arch.hw_mmu->pgt;
if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;
@ -1271,7 +1281,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
}
out_unlock:
write_unlock(&kvm->mmu_lock);
if (logging_perm_fault)
read_unlock(&kvm->mmu_lock);
else
write_unlock(&kvm->mmu_lock);
kvm_set_pfn_accessed(pfn);
kvm_release_pfn_clean(pfn);
return ret != -EAGAIN ? ret : 0;