[PATCH 3.13 103/187] KVM: PPC: Book3S PR: Take SRCU read lock around RTAS kvm_read_guest() call

Kamal Mostafa kamal at canonical.com
Mon Sep 15 22:08:33 UTC 2014 -stable review patch.  If anyone has any objections, please let me know.


From: Paul Mackerras <paulus at samba.org>

commit ef1af2e29622ff3403926ae801a2b10da075a2de upstream.

This does for PR KVM what c9438092cae4 ("KVM: PPC: Book3S HV: Take SRCU
read lock around kvm_read_guest() call") did for HV KVM, that is,
eliminate a "suspicious rcu_dereference_check() usage!" warning by
taking the SRCU lock around the call to kvmppc_rtas_hcall().

It also fixes a return of RESUME_HOST to return EMULATE_FAIL instead,
since kvmppc_h_pr() is supposed to return EMULATE_* values.

Signed-off-by: Paul Mackerras <paulus at samba.org>
Signed-off-by: Alexander Graf <agraf at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 arch/powerpc/kvm/book3s_pr_papr.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
index 5efa97b..7a801b5 100644
--- a/arch/powerpc/kvm/book3s_pr_papr.c
+++ b/arch/powerpc/kvm/book3s_pr_papr.c
@@ -258,6 +258,8 @@ static int kvmppc_h_pr_xics_hcall(struct kvm_vcpu *vcpu, u32 cmd)
 int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
+	int rc, idx;
 	switch (cmd) {
 	case H_ENTER:
 		return kvmppc_h_pr_enter(vcpu);
@@ -286,8 +288,11 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
 	case H_RTAS:
 		if (list_empty(&vcpu->kvm->arch.rtas_tokens))
-			return RESUME_HOST;
-		if (kvmppc_rtas_hcall(vcpu))
+			break;
+		idx = srcu_read_lock(&vcpu->kvm->srcu);
+		rc = kvmppc_rtas_hcall(vcpu);
+		srcu_read_unlock(&vcpu->kvm->srcu, idx);
+		if (rc)
 		kvmppc_set_gpr(vcpu, 3, 0);
 		return EMULATE_DONE;

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