From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Li RongQing <lirongqing@baidu.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sasha Levin <sashal@kernel.org>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org
Subject: [PATCH MANUALSEL 5.10] KVM: x86: Yield to IPI target vCPU only if it is busy
Date: Wed, 9 Mar 2022 11:46:44 -0500 [thread overview]
Message-ID: <20220309164645.138079-1-sashal@kernel.org> (raw)
From: Li RongQing <lirongqing@baidu.com>
[ Upstream commit 9ee83635d872812f3920209c606c6ea9e412ffcc ]
When sending a call-function IPI-many to vCPUs, yield to the
IPI target vCPU which is marked as preempted.
but when emulating HLT, an idling vCPU will be voluntarily
scheduled out and mark as preempted from the guest kernel
perspective. yielding to idle vCPU is pointless and increase
unnecessary vmexit, maybe miss the true preempted vCPU
so yield to IPI target vCPU only if vCPU is busy and preempted
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Message-Id: <1644380201-29423-1-git-send-email-lirongqing@baidu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/kvm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 7462b79c39de..8fe6eb5bed3f 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -590,7 +590,7 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
/* Make sure other vCPUs get a chance to run if they need to. */
for_each_cpu(cpu, mask) {
- if (vcpu_is_preempted(cpu)) {
+ if (!idle_cpu(cpu) && vcpu_is_preempted(cpu)) {
kvm_hypercall1(KVM_HC_SCHED_YIELD, per_cpu(x86_cpu_to_apicid, cpu));
break;
}
--
2.34.1
next reply other threads:[~2022-03-09 16:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 16:46 Sasha Levin [this message]
2022-03-09 16:51 ` [PATCH MANUALSEL 5.10] KVM: x86: Yield to IPI target vCPU only if it is busy Paolo Bonzini
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