From: Oliver Upton <oliver.upton@linux.dev>
Date: Fri, 2 Dec 2022 18:51:55 +0000 (+0000)
Subject: KVM: arm64: Handle access faults behind the read lock
X-Git-Tag: v6.6.7~3413^2~2^2^2~6^2~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=fc61f554e6947edd21cd84fb814f8418349a3569;p=platform%2Fkernel%2Flinux-starfive.git

KVM: arm64: Handle access faults behind the read lock

As the underlying software walkers are able to traverse and update
stage-2 in parallel there is no need to serialize access faults.

Only take the read lock when handling an access fault.

Link: https://lore.kernel.org/r/20221202185156.696189-6-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index aa36d89..30575b5 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -1120,7 +1120,8 @@ kvm_pte_t kvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr)
 
 	ret = stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
 				       &pte, NULL,
-				       KVM_PGTABLE_WALK_HANDLE_FAULT);
+				       KVM_PGTABLE_WALK_HANDLE_FAULT |
+				       KVM_PGTABLE_WALK_SHARED);
 	if (!ret)
 		dsb(ishst);
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index edfbe85..d24ce2d 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1406,10 +1406,10 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
 
 	trace_kvm_access_fault(fault_ipa);
 
-	write_lock(&vcpu->kvm->mmu_lock);
+	read_lock(&vcpu->kvm->mmu_lock);
 	mmu = vcpu->arch.hw_mmu;
 	pte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
-	write_unlock(&vcpu->kvm->mmu_lock);
+	read_unlock(&vcpu->kvm->mmu_lock);
 
 	if (kvm_pte_valid(pte))
 		kvm_set_pfn_accessed(kvm_pte_to_pfn(pte));