Subject: [PATCH] powerpc: kvm: make the setup of hpte under the protection of KVMPPC_RMAP_LOCK_BIT

From: Liu Ping Fan <[email-masked]>
Date: Mon, 28 Jul 2014 14:09:04 +0800

In current code, the setup of hpte is under the risk of race with
mmu_notifier_invalidate, i.e we may setup a hpte with a invalid pfn.
Resolve this issue by sync the two actions by KVMPPC_RMAP_LOCK_BIT.

Signed-off-by: Liu Ping Fan <[email-masked]>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 8056107..e6dcff4 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -754,19 +754,24 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 
 	if (hptep[0] & HPTE_V_VALID) {
 		/* HPTE was previously valid, so we need to invalidate it */
-		unlock_rmap(rmap);
 		hptep[0] |= HPTE_V_ABSENT;
 		kvmppc_invalidate_hpte(kvm, hptep, index);
 		/* don't lose previous R and C bits */
 		r |= hptep[1] & (HPTE_R_R | HPTE_R_C);
+
+		hptep[1] = r;
+		eieio();
+		hptep[0] = hpte[0];
+		asm volatile("ptesync" : : : "memory");
+		unlock_rmap(rmap);
 	} else {
+		hptep[1] = r;
+		eieio();
+		hptep[0] = hpte[0];
+		asm volatile("ptesync" : : : "memory");
 		kvmppc_add_revmap_chain(kvm, rev, rmap, index, 0);
 	}
 
-	hptep[1] = r;
-	eieio();
-	hptep[0] = hpte[0];
-	asm volatile("ptesync" : : : "memory");
 	preempt_enable();
 	if (page && hpte_is_writable(r))
 		SetPageDirty(page);
-- 
1.8.1.4