On Tue, 6 Aug 2019 at 07:17, Paolo Bonzini pbonzini@redhat.com wrote:
On 05/08/19 04:03, Wanpeng Li wrote:
From: Wanpeng Li wanpengli@tencent.com
After commit d73eb57b80b (KVM: Boost vCPUs that are delivering interrupts), a five years old bug is exposed. Running ebizzy benchmark in three 80 vCPUs VMs on one 80 pCPUs Skylake server, a lot of rcu_sched stall warning splatting in the VMs after stress testing:
INFO: rcu_sched detected stalls on CPUs/tasks: { 4 41 57 62 77} (detected by 15, t=60004 jiffies, g=899, c=898, q=15073) Call Trace: flush_tlb_mm_range+0x68/0x140 tlb_flush_mmu.part.75+0x37/0xe0 tlb_finish_mmu+0x55/0x60 zap_page_range+0x142/0x190 SyS_madvise+0x3cd/0x9c0 system_call_fastpath+0x1c/0x21
swait_active() sustains to be true before finish_swait() is called in kvm_vcpu_block(), voluntarily preempted vCPUs are taken into account by kvm_vcpu_on_spin() loop greatly increases the probability condition kvm_arch_vcpu_runnable(vcpu) is checked and can be true, when APICv is enabled the yield-candidate vCPU's VMCS RVI field leaks(by vmx_sync_pir_to_irr()) into spinning-on-a-taken-lock vCPU's current VMCS.
This patch fixes it by checking conservatively a subset of events.
Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Cc: Christian Borntraeger borntraeger@de.ibm.com Cc: Marc Zyngier Marc.Zyngier@arm.com Cc: stable@vger.kernel.org Fixes: 98f4a1467 (KVM: add kvm_arch_vcpu_runnable() test to kvm_vcpu_on_spin() loop) Signed-off-by: Wanpeng Li wanpengli@tencent.com
v3 -> v4:
- just test KVM_REQ_*
- rename the hook to apicv_has_pending_interrupt
- wrap with #ifdef CONFIG_KVM_ASYNC_PF
v2 -> v3:
- check conservatively a subset of events
v1 -> v2:
- checking swait_active(&vcpu->wq) for involuntary preemption
arch/mips/kvm/mips.c | 5 +++++ arch/powerpc/kvm/powerpc.c | 5 +++++ arch/s390/kvm/kvm-s390.c | 5 +++++ arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/svm.c | 6 ++++++ arch/x86/kvm/vmx/vmx.c | 6 ++++++ arch/x86/kvm/x86.c | 16 ++++++++++++++++ include/linux/kvm_host.h | 1 + virt/kvm/arm/arm.c | 5 +++++ virt/kvm/kvm_main.c | 16 +++++++++++++++- 10 files changed, 65 insertions(+), 1 deletion(-)
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 2cfe839..95a4642 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -98,6 +98,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu) return !!(vcpu->arch.pending_exceptions); }
+bool kvm_arch_dy_runnable(struct kvm_vcpu *vcpu)
Using a __weak definition for the default implementation is a bit more concise. Queued with that change.
Thank you, Paolo! Btw, how about other 5 patches?
Regards, Wanpeng Li