Commit f783ef1c authored by Jing Zhang's avatar Jing Zhang Committed by Marc Zyngier
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KVM: arm64: Add fast path to handle permission relaxation during dirty logging 



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

Signed-off-by: default avatarJing Zhang <jingzhangos@google.com>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220118015703.3630552-3-jingzhangos@google.com
parent fcc5bf89

arch/arm64/kvm/mmu.c

+15 −2
Original line number Diff line number Diff line
@@ -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);

	}
@@ -1212,6 +1214,14 @@ 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 (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))
@@ -1271,6 +1281,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, 
	}



out_unlock:

	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);