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Message-Id: <20220314112744.738007397@linuxfoundation.org>
Date: Mon, 14 Mar 2022 12:54:03 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 061/110] x86/kvm: Dont use pv tlb/ipi/sched_yield if on 1 vCPU
From: Wanpeng Li <wanpengli@...cent.com>
[ Upstream commit ec756e40e271866f951d77c5e923d8deb6002b15 ]
Inspired by commit 3553ae5690a (x86/kvm: Don't use pvqspinlock code if
only 1 vCPU), on a VM with only 1 vCPU, there is no need to enable
pv tlb/ipi/sched_yield and we can save the memory for __pv_cpu_mask.
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
Message-Id: <1645171838-2855-1-git-send-email-wanpengli@...cent.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
arch/x86/kernel/kvm.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b656456c3a94..811c7aaf23aa 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -457,19 +457,22 @@ static bool pv_tlb_flush_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
!kvm_para_has_hint(KVM_HINTS_REALTIME) &&
- kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
+ kvm_para_has_feature(KVM_FEATURE_STEAL_TIME) &&
+ (num_possible_cpus() != 1));
}
static bool pv_ipi_supported(void)
{
- return kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI);
+ return (kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI) &&
+ (num_possible_cpus() != 1));
}
static bool pv_sched_yield_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
!kvm_para_has_hint(KVM_HINTS_REALTIME) &&
- kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
+ kvm_para_has_feature(KVM_FEATURE_STEAL_TIME) &&
+ (num_possible_cpus() != 1));
}
#define KVM_IPI_CLUSTER_SIZE (2 * BITS_PER_LONG)
--
2.34.1
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