From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Lynch <nathanl@linux.ibm.com>,
Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Phil Auld <pauld@redhat.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Juri Lelli <juri.lelli@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Waiman Long <longman@redhat.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Valentin Schneider <valentin.schneider@arm.com>
Subject: [PATCH 4/4] powerpc/paravirt: Use is_kvm_guest in vcpu_is_preempted
Date: Wed, 28 Oct 2020 18:05:12 +0530 [thread overview]
Message-ID: <20201028123512.871051-5-srikar@linux.vnet.ibm.com> (raw)
In-Reply-To: <20201028123512.871051-1-srikar@linux.vnet.ibm.com>
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 <srikar@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Phil Auld <pauld@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
next prev parent reply other threads:[~2020-10-28 12:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-28 12:35 [PATCH 0/4] Powerpc: Better preemption for shared processor Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 1/4] powerpc: Refactor is_kvm_guest declaration to new header Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 2/4] powerpc: Rename is_kvm_guest to check_kvm_guest Srikar Dronamraju
2020-10-28 12:35 ` [PATCH 3/4] powerpc: Reintroduce is_kvm_guest in a new avatar Srikar Dronamraju
2020-10-28 12:35 ` Srikar Dronamraju [this message]
2020-10-29 0:01 ` [PATCH 0/4] Powerpc: Better preemption for shared processor Waiman Long
2020-10-29 7:14 ` Srikar Dronamraju
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