Subject: [PATCH v5 07/11] powerpc/kvm/e500: Applies counting method to monitor lockless pgtbl walks

From: Leonardo Bras <[email-masked]>
Date: Wed, 2 Oct 2019 22:33:21 -0300

Applies the counting-based method for monitoring lockless pgtable walks on
kvmppc_e500_shadow_map().

Fixes the place where local_irq_restore() is called: previously, if ptep
was NULL, local_irq_restore() would never be called.

local_irq_{save,restore} is already inside {begin,end}_lockless_pgtbl_walk,
so there is no need to repeat it here.

Variable that saves the	irq mask was renamed from flags to irq_mask so it
doesn't lose meaning now it's not directly passed to local_irq_* functions.

Signed-off-by: Leonardo Bras <[email-masked]>
---
 arch/powerpc/kvm/e500_mmu_host.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 321db0fdb9db..36f07c6a5f10 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -336,7 +336,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 	pte_t *ptep;
 	unsigned int wimg = 0;
 	pgd_t *pgdir;
-	unsigned long flags;
+	unsigned long irq_mask;
 
 	/* used to check for invalidations in progress */
 	mmu_seq = kvm->mmu_notifier_seq;
@@ -473,7 +473,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 	 * We are holding kvm->mmu_lock so a notifier invalidate
 	 * can't run hence pfn won't change.
 	 */
-	local_irq_save(flags);
+	irq_mask = begin_lockless_pgtbl_walk(kvm->mm);
 	ptep = find_linux_pte(pgdir, hva, NULL, NULL);
 	if (ptep) {
 		pte_t pte = READ_ONCE(*ptep);
@@ -481,15 +481,16 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 		if (pte_present(pte)) {
 			wimg = (pte_val(pte) >> PTE_WIMGE_SHIFT) &
 				MAS2_WIMGE_MASK;
-			local_irq_restore(flags);
 		} else {
-			local_irq_restore(flags);
+			end_lockless_pgtbl_walk(kvm->mm, irq_mask);
 			pr_err_ratelimited("%s: pte not present: gfn %lx,pfn %lx\n",
 					   __func__, (long)gfn, pfn);
 			ret = -EINVAL;
 			goto out;
 		}
 	}
+	end_lockless_pgtbl_walk(kvm->mm, irq_mask);
+
 	kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);
 
 	kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
-- 
2.20.1