No functional change in this patch. A helper is added to find if
vcpu is dispatched by hypervisor. Use that instead of opencoding.
Also clarify some of the comments.
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
arch/powerpc/include/asm/paravirt.h | 33 ++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/include/asm/paravirt.h
b/arch/powerpc/include/asm/paravirt.h
index ac4279208d63..b78b82d66057 100644
--- a/arch/powerpc/include/asm/paravirt.h
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -76,6 +76,17 @@ static inline bool is_vcpu_idle(int vcpu)
{
return lppaca_of(vcpu).idle;
}
+
+static inline bool vcpu_is_dispatched(int vcpu)
+{
+ /*
+ * This is the yield_count. An "odd" value (low bit on) means that
+ * the processor is yielded (either because of an OS yield or a
+ * hypervisor preempt). An even value implies that the processor is
+ * currently executing.
+ */
+ return (!(yield_count_of(vcpu) & 1));
+}
#else
static inline bool is_shared_processor(void)
{
@@ -109,6 +120,10 @@ static inline bool is_vcpu_idle(int vcpu)
{
return false;
}
+static inline bool vcpu_is_dispatched(int vcpu)
+{
+ return true;
+}
#endif
#define vcpu_is_preempted vcpu_is_preempted
@@ -134,12 +149,12 @@ static inline bool vcpu_is_preempted(int cpu)
* If the hypervisor has dispatched the target CPU on a physical
* processor, then the target CPU is definitely not preempted.
*/
- if (!(yield_count_of(cpu) & 1))
+ if (vcpu_is_dispatched(cpu))
return false;
/*
- * If the target CPU has yielded to Hypervisor but OS has not
- * requested idle then the target CPU is definitely preempted.
+ * if the target CPU is not dispatched and the guest OS
+ * has not marked the CPU idle, then it is hypervisor preempted.
*/
if (!is_vcpu_idle(cpu))
return true;
@@ -166,7 +181,7 @@ static inline bool vcpu_is_preempted(int cpu)
/*
* The PowerVM hypervisor dispatches VMs on a whole core
- * basis. So we know that a thread sibling of the local CPU
+ * basis. So we know that a thread sibling of the executing CPU
* cannot have been preempted by the hypervisor, even if it
* has called H_CONFER, which will set the yield bit.
*/
@@ -174,15 +189,17 @@ static inline bool vcpu_is_preempted(int cpu)
return false;
/*
- * If any of the threads of the target CPU's core are not
- * preempted or ceded, then consider target CPU to be
- * non-preempted.
+ * The specific target CPU was marked by guest OS as idle, but
+ * then also check all other cpus in the core for PowerVM
+ * because it does core scheduling and one of the vcpu
+ * of the core getting preempted by hypervisor implies
+ * other vcpus can also be considered preempted.
*/
first_cpu = cpu_first_thread_sibling(cpu);
for (i = first_cpu; i < first_cpu + threads_per_core; i++) {
if (i == cpu)
continue;
- if (!(yield_count_of(i) & 1))
+ if (vcpu_is_dispatched(i))
return false;
if (!is_vcpu_idle(i))
return true;
--
2.41.0
