On 05/08/19 04:03, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Cc: Marc Zyngier <Marc.Zyngier@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 98f4a1467 (KVM: add kvm_arch_vcpu_runnable() test to kvm_vcpu_on_spin() loop)
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> 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.
Paolo
