linux-kernel - [PATCH v2 2/2] KVM: X86: Avoid traversing all the cpus for pv tlb flush when steal time is disabled

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Date:   Sun,  4 Feb 2018 22:57:58 -0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH v2 2/2] KVM: X86: Avoid traversing all the cpus for pv tlb flush when steal time is disabled

From: Wanpeng Li <wanpengli@...cent.com>

Avoid traversing all the cpus for pv tlb flush when steal time 
is disabled since pv tlb flush depends on the field in steal time 
for shared data.

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kernel/kvm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index f2a09cf..4f3c997 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -546,7 +546,8 @@ static void __init kvm_guest_init(void)
 	}
 
 	if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
-			!kvm_para_has_feature(KVM_FEATURE_PV_DEDICATED))
+			!kvm_para_has_feature(KVM_FEATURE_PV_DEDICATED) &&
+			kvm_para_has_feature(KVM_FEATURE_STEAL_TIME))
 		pv_mmu_ops.flush_tlb_others = kvm_flush_tlb_others;
 
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
@@ -635,7 +636,8 @@ static __init int kvm_setup_pv_tlb_flush(void)
 	int cpu;
 
 	if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
-			!kvm_para_has_feature(KVM_FEATURE_PV_DEDICATED)) {
+			!kvm_para_has_feature(KVM_FEATURE_PV_DEDICATED) &&
+			kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 		for_each_possible_cpu(cpu) {
 			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_tlb_mask, cpu),
 				GFP_KERNEL, cpu_to_node(cpu));
-- 
2.7.4