[PATCH v2 09/11] powerpc/kvm/book3s_64: Applies counting method to monitor lockless pgtbl walks

[Leonardo Bras]

Applies the counting-based method for monitoring all book3s_64-related
functions that do lockless pagetable walks.

Signed-off-by: Leonardo Bras <leonardo@xxxxxxxxxxxxx>
---
It may be necessary to merge an older patch first:
powerpc: kvm: Reduce calls to get current->mm by storing the value locally
Link: https://lore.kernel.org/linuxppc-dev/20190919222748.20761-1-leonardo@xxxxxxxxxxxxx/

 arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 ++
 arch/powerpc/kvm/book3s_64_mmu_radix.c | 20 ++++++++++++++++++--
 arch/powerpc/kvm/book3s_64_vio_hv.c    |  4 ++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index f2b9aea43216..a938733c3f7b 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -622,6 +622,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			 * We need to protect against page table destruction
 			 * hugepage split and collapse.
 			 */
+			start_lockless_pgtbl_walk(mm);
 			local_irq_save(flags);
 			ptep = find_current_mm_pte(mm->pgd, hva, NULL, NULL);
 			if (ptep) {
@@ -630,6 +631,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 					write_ok = 1;
 			}
 			local_irq_restore(flags);
+			end_lockless_pgtbl_walk(mm);
 		}
 	}
 
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 2d415c36a61d..d46f8258d8d6 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -741,6 +741,7 @@ bool kvmppc_hv_handle_set_rc(struct kvm *kvm, pgd_t *pgtable, bool writing,
 	unsigned long pgflags;
 	unsigned int shift;
 	pte_t *ptep;
+	bool ret = false;
 
 	/*
 	 * Need to set an R or C bit in the 2nd-level tables;
@@ -755,12 +756,14 @@ bool kvmppc_hv_handle_set_rc(struct kvm *kvm, pgd_t *pgtable, bool writing,
 	 * We can do this without disabling irq because the Linux MM
 	 * subsystem doesn't do THP splits and collapses on this tree.
 	 */
+	start_lockless_pgtbl_walk(kvm->mm);
 	ptep = __find_linux_pte(pgtable, gpa, NULL, &shift);
 	if (ptep && pte_present(*ptep) && (!writing || pte_write(*ptep))) {
 		kvmppc_radix_update_pte(kvm, ptep, 0, pgflags, gpa, shift);
-		return true;
+		ret = true;
 	}
-	return false;
+	end_lockless_pgtbl_walk(kvm->mm);
+	return ret;
 }
 
 int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
@@ -813,6 +816,7 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 	 * Read the PTE from the process' radix tree and use that
 	 * so we get the shift and attribute bits.
 	 */
+	start_lockless_pgtbl_walk(kvm->mm);
 	local_irq_disable();
 	ptep = __find_linux_pte(vcpu->arch.pgdir, hva, NULL, &shift);
 	/*
@@ -821,12 +825,14 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 	 */
 	if (!ptep) {
 		local_irq_enable();
+		end_lockless_pgtbl_walk(kvm->mm);
 		if (page)
 			put_page(page);
 		return RESUME_GUEST;
 	}
 	pte = *ptep;
 	local_irq_enable();
+	end_lockless_pgtbl_walk(kvm->mm);
 
 	/* If we're logging dirty pages, always map single pages */
 	large_enable = !(memslot->flags & KVM_MEM_LOG_DIRTY_PAGES);
@@ -972,10 +978,12 @@ int kvm_unmap_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
 	unsigned long gpa = gfn << PAGE_SHIFT;
 	unsigned int shift;
 
+	start_lockless_pgtbl_walk(kvm->mm);
 	ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
 	if (ptep && pte_present(*ptep))
 		kvmppc_unmap_pte(kvm, ptep, gpa, shift, memslot,
 				 kvm->arch.lpid);
+	end_lockless_pgtbl_walk(kvm->mm);
 	return 0;				
 }
 
@@ -989,6 +997,7 @@ int kvm_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
 	int ref = 0;
 	unsigned long old, *rmapp;
 
+	start_lockless_pgtbl_walk(kvm->mm);
 	ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
 	if (ptep && pte_present(*ptep) && pte_young(*ptep)) {
 		old = kvmppc_radix_update_pte(kvm, ptep, _PAGE_ACCESSED, 0,
@@ -1001,6 +1010,7 @@ int kvm_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
 					       1UL << shift);
 		ref = 1;
 	}
+	end_lockless_pgtbl_walk(kvm->mm);
 	return ref;
 }
 
@@ -1013,9 +1023,11 @@ int kvm_test_age_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
 	unsigned int shift;
 	int ref = 0;
 
+	start_lockless_pgtbl_walk(kvm->mm);
 	ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
 	if (ptep && pte_present(*ptep) && pte_young(*ptep))
 		ref = 1;
+	end_lockless_pgtbl_walk(kvm->mm);
 	return ref;
 }
 
@@ -1030,6 +1042,7 @@ static int kvm_radix_test_clear_dirty(struct kvm *kvm,
 	int ret = 0;
 	unsigned long old, *rmapp;
 
+	start_lockless_pgtbl_walk(kvm->mm);
 	ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
 	if (ptep && pte_present(*ptep) && pte_dirty(*ptep)) {
 		ret = 1;
@@ -1046,6 +1059,7 @@ static int kvm_radix_test_clear_dirty(struct kvm *kvm,
 					       1UL << shift);
 		spin_unlock(&kvm->mmu_lock);
 	}
+	end_lockless_pgtbl_walk(kvm->mm);
 	return ret;
 }
 
@@ -1084,6 +1098,7 @@ void kvmppc_radix_flush_memslot(struct kvm *kvm,
 
 	gpa = memslot->base_gfn << PAGE_SHIFT;
 	spin_lock(&kvm->mmu_lock);
+	start_lockless_pgtbl_walk(kvm->mm);
 	for (n = memslot->npages; n; --n) {
 		ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
 		if (ptep && pte_present(*ptep))
@@ -1091,6 +1106,7 @@ void kvmppc_radix_flush_memslot(struct kvm *kvm,
 					 kvm->arch.lpid);
 		gpa += PAGE_SIZE;
 	}
+	end_lockless_pgtbl_walk(kvm->mm);
 	spin_unlock(&kvm->mmu_lock);
 }
 
diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
index b4f20f13b860..d7ea44f28993 100644
--- a/arch/powerpc/kvm/book3s_64_vio_hv.c
+++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
@@ -431,6 +431,7 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
 static long kvmppc_rm_ua_to_hpa(struct kvm_vcpu *vcpu,
 		unsigned long ua, unsigned long *phpa)
 {
+	struct kvm *kvm = vcpu->kvm;
 	pte_t *ptep, pte;
 	unsigned shift = 0;
 
@@ -443,10 +444,13 @@ static long kvmppc_rm_ua_to_hpa(struct kvm_vcpu *vcpu,
 	 * to exit which will agains result in the below page table walk
 	 * to finish.
 	 */
+
+	start_lockless_pgtbl_walk(kvm->mm);
 	ptep = __find_linux_pte(vcpu->arch.pgdir, ua, NULL, &shift);
 	if (!ptep || !pte_present(*ptep))
 		return -ENXIO;
 	pte = *ptep;
+	end_lockless_pgtbl_walk(kvm->mm);
 
 	if (!shift)
 		shift = PAGE_SHIFT;
-- 
2.20.1