linux-kernel - [PATCH 4.14 19/62] KVM: PPC: Book3S HV: Fix guest time accounting with VIRT_CPU_ACCOUNTING

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Message-Id: <20180514064817.473327191@linuxfoundation.org>
Date:   Mon, 14 May 2018 08:48:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Laurent Vivier <lvivier@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Paul Mackerras <paulus@...abs.org>
Subject: [PATCH 4.14 19/62] KVM: PPC: Book3S HV: Fix guest time accounting with VIRT_CPU_ACCOUNTING_GEN

4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Laurent Vivier <lvivier@...hat.com>

commit 61bd0f66ff92d5ce765ff9850fd3cbfec773c560 upstream.

Since commit 8b24e69fc47e ("KVM: PPC: Book3S HV: Close race with testing
for signals on guest entry"), if CONFIG_VIRT_CPU_ACCOUNTING_GEN is set, the
guest time is not accounted to guest time and user time, but instead to
system time.

This is because guest_enter()/guest_exit() are called while interrupts
are disabled and the tick counter cannot be updated between them.

To fix that, move guest_exit() after local_irq_enable(), and as
guest_enter() is called with IRQ disabled, call guest_enter_irqoff()
instead.

Fixes: 8b24e69fc47e ("KVM: PPC: Book3S HV: Close race with testing for signals on guest entry")
Signed-off-by: Laurent Vivier <lvivier@...hat.com>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kvm/book3s_hv.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2847,7 +2847,7 @@ static noinline void kvmppc_run_core(str
 	 */
 	trace_hardirqs_on();
 
-	guest_enter();
+	guest_enter_irqoff();
 
 	srcu_idx = srcu_read_lock(&vc->kvm->srcu);
 
@@ -2855,8 +2855,6 @@ static noinline void kvmppc_run_core(str
 
 	srcu_read_unlock(&vc->kvm->srcu, srcu_idx);
 
-	guest_exit();
-
 	trace_hardirqs_off();
 	set_irq_happened(trap);
 
@@ -2890,6 +2888,7 @@ static noinline void kvmppc_run_core(str
 	kvmppc_set_host_core(pcpu);
 
 	local_irq_enable();
+	guest_exit();
 
 	/* Let secondaries go back to the offline loop */
 	for (i = 0; i < controlled_threads; ++i) {