kvm/x86: Hyper-V fix SynIC timer disabling condition

Andrey Smetanin · bonzini · commit 23a3b201fd18 · 2016-01-08T19:04:41.000+01:00
Hypervisor Function Specification(HFS) doesn't require
to disable SynIC timer at timer config write if timer-&gt;count = 0.

So drop this check, this allow to load timers MSR's
during migration restore, because config are set before count
in QEMU side.

Also fix condition according to HFS doc(15.3.1):
"It is not permitted to set the SINTx field to zero for an
enabled timer. If attempted, the timer will be
marked disabled (that is, bit 0 cleared) immediately."

Signed-off-by: Andrey Smetanin &lt;asmetanin@virtuozzo.com&gt;
Reviewed-by: Roman Kagan &lt;rkagan@virtuozzo.com&gt;
CC: Gleb Natapov &lt;gleb@kernel.org&gt;
CC: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
CC: Roman Kagan &lt;rkagan@virtuozzo.com&gt;
CC: Denis V. Lunev &lt;den@openvz.org&gt;
CC: qemu-devel@nongnu.org
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
@@ -474,7 +474,7 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)
 static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
 			     bool host)
 {
-	if (stimer->count == 0 || HV_STIMER_SINT(config) == 0)
+	if ((stimer->config & HV_STIMER_ENABLE) && HV_STIMER_SINT(config) == 0)
 		config &= ~HV_STIMER_ENABLE;
 	stimer->config = config;
 	stimer_cleanup(stimer);

Original file line number	Diff line number	Diff line change
`@@ -474,7 +474,7 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)`
`474`	`474`	`static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,`
`475`	`475`	`bool host)`
`476`	`476`	`{`
`477`		`- if (stimer->count == 0 \|\| HV_STIMER_SINT(config) == 0)`
	`477`	`+ if ((stimer->config & HV_STIMER_ENABLE) && HV_STIMER_SINT(config) == 0)`
`478`	`478`	`config &= ~HV_STIMER_ENABLE;`
`479`	`479`	`stimer->config = config;`
`480`	`480`	`stimer_cleanup(stimer);`