From: Wanpeng Li Date: Fri, 18 Feb 2022 08:10:38 +0000 (-0800) Subject: x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU X-Git-Tag: v5.16.15~53 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=4e68c4b475672592c71b4a7d1f1aff93c419e451;p=thirdparty%2Fkernel%2Fstable.git x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU [ 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 Message-Id: <1645171838-2855-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 59abbdad7729c..ff3db164e52cb 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -462,19 +462,22 @@ 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)