From: Yi Wang <up2wing@gmail.com>
To: seanjc@google.com, pbonzini@redhat.com, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, wanpengli@tencent.com,
foxywang@tencent.com, oliver.upton@linux.dev, maz@kernel.org,
anup@brainfault.org, atishp@atishpatra.org,
borntraeger@linux.ibm.com, frankja@linux.ibm.com,
imbrenda@linux.ibm.com, weijiang.yang@intel.com
Cc: up2wing@gmail.com
Subject: [v4 RESEND 2/3] KVM: x86: don't setup empty irq routing when KVM_CAP_SPLIT_IRQCHIP
Date: Fri, 26 Apr 2024 12:15:58 +0800 [thread overview]
Message-ID: <20240426041559.3717884-3-foxywang@tencent.com> (raw)
In-Reply-To: <20240426041559.3717884-1-foxywang@tencent.com>
From: Yi Wang <foxywang@tencent.com>
We found that it may cost more than 20 milliseconds very accidentally
to enable cap of KVM_CAP_SPLIT_IRQCHIP on a host which has many vms
already.
The reason is that when vmm(qemu/CloudHypervisor) invokes
KVM_CAP_SPLIT_IRQCHIP kvm will call synchronize_srcu_expedited() and
might_sleep and kworker of srcu may cost some delay during this period.
As we have set up empty irq routing when creating vm, so this is no
need now.
Signed-off-by: Yi Wang <foxywang@tencent.com>
---
arch/x86/kvm/irq.h | 1 -
arch/x86/kvm/irq_comm.c | 5 -----
arch/x86/kvm/x86.c | 3 ---
3 files changed, 9 deletions(-)
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index c2d7cfe82d00..76d46b2f41dd 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -106,7 +106,6 @@ void __kvm_migrate_timers(struct kvm_vcpu *vcpu);
int apic_has_pending_timer(struct kvm_vcpu *vcpu);
int kvm_setup_default_irq_routing(struct kvm *kvm);
-int kvm_setup_empty_irq_routing(struct kvm *kvm);
int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq,
struct dest_map *dest_map);
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 68f3f6c26046..6ee7ca39466e 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -397,11 +397,6 @@ int kvm_setup_default_irq_routing(struct kvm *kvm)
static const struct kvm_irq_routing_entry empty_routing[] = {};
-int kvm_setup_empty_irq_routing(struct kvm *kvm)
-{
- return kvm_set_irq_routing(kvm, empty_routing, 0, 0);
-}
-
void kvm_arch_post_irq_routing_update(struct kvm *kvm)
{
if (!irqchip_split(kvm))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 91478b769af0..01270182757b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6527,9 +6527,6 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
goto split_irqchip_unlock;
if (kvm->created_vcpus)
goto split_irqchip_unlock;
- r = kvm_setup_empty_irq_routing(kvm);
- if (r)
- goto split_irqchip_unlock;
/* Pairs with irqchip_in_kernel. */
smp_wmb();
kvm->arch.irqchip_mode = KVM_IRQCHIP_SPLIT;
--
2.39.3
next prev parent reply other threads:[~2024-04-26 4:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 4:15 [v4 RESEND 0/3] KVM: irqchip: synchronize srcu only if needed Yi Wang
2024-04-26 4:15 ` [v4 RESEND 1/3] KVM: setup empty irq routing when create vm Yi Wang
2024-05-03 22:08 ` Sean Christopherson
2024-05-05 4:56 ` Yi Wang
2024-04-26 4:15 ` Yi Wang [this message]
2024-04-26 4:15 ` [v4 RESEND 3/3] KVM: s390: don't setup dummy routing when KVM_CREATE_IRQCHIP Yi Wang
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