If its a shared lpar but not a KVM guest, then see if the vCPU is
related to the calling vCPU. On PowerVM, only cores can be preempted.
So if one vCPU is a non-preempted state, we can decipher that all other
vCPUs sharing the same core are in non-preempted state.
Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-ker...@vger.kernel.org>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Nathan Lynch <nath...@linux.ibm.com>
Cc: Gautham R Shenoy <e...@linux.vnet.ibm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Valentin Schneider <valentin.schnei...@arm.com>
Cc: Juri Lelli <juri.le...@redhat.com>
Cc: Waiman Long <long...@redhat.com>
Cc: Phil Auld <pa...@redhat.com>
---
arch/powerpc/include/asm/paravirt.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/powerpc/include/asm/paravirt.h
b/arch/powerpc/include/asm/paravirt.h
index 9362c94fe3aa..edc08f04aef7 100644
--- a/arch/powerpc/include/asm/paravirt.h
+++ b/arch/powerpc/include/asm/paravirt.h
@@ -10,6 +10,9 @@
#endif
#ifdef CONFIG_PPC_SPLPAR
+#include <asm/kvm_guest.h>
+#include <asm/cputhreads.h>
+
DECLARE_STATIC_KEY_FALSE(shared_processor);
static inline bool is_shared_processor(void)
@@ -74,6 +77,21 @@ static inline bool vcpu_is_preempted(int cpu)
{
if (!is_shared_processor())
return false;
+
+#ifdef CONFIG_PPC_SPLPAR
+ if (!is_kvm_guest()) {
+ int first_cpu = cpu_first_thread_sibling(smp_processor_id());
+
+ /*
+ * Preemption can only happen at core granularity. This CPU
+ * is not preempted if one of the CPU of this core is not
+ * preempted.
+ */
+ if (cpu_first_thread_sibling(cpu) == first_cpu)
+ return false;
+ }
+#endif
+
if (yield_count_of(cpu) & 1)
return true;
return false;
--
2.18.4
