linux-kernel - [PATCH 3.16 124/233] kvm: async_pf: fix rcu_irq

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Date:   Sat, 09 Sep 2017 22:47:14 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Paolo Bonzini" <pbonzini@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        "Wanpeng Li" <wanpeng.li@...mail.com>,
        "Radim Krčmář" <rkrcmar@...hat.com>,
        "Ross Zwisler" <ross.zwisler@...ux.intel.com>
Subject: [PATCH 3.16 124/233] kvm: async_pf: fix rcu_irq_enter() with irqs
 enabled

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@...hat.com>

commit bbaf0e2b1c1b4f88abd6ef49576f0efb1734eae5 upstream.

native_safe_halt enables interrupts, and you just shouldn't
call rcu_irq_enter() with interrupts enabled.  Reorder the
call with the following local_irq_disable() to respect the
invariant.

Reported-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Tested-by: Wanpeng Li <wanpeng.li@...mail.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kernel/kvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -160,8 +160,8 @@ void kvm_async_pf_task_wait(u32 token)
 			 */
 			rcu_irq_exit();
 			native_safe_halt();
-			rcu_irq_enter();
 			local_irq_disable();
+			rcu_irq_enter();
 		}
 	}
 	if (!n.halted)