From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
stable@vger.kernel.org
Subject: [PATCH v2 3/3] KVM: Fix leak vCPU's VMCS value into other pCPU
Date: Wed, 31 Jul 2019 19:39:58 +0800 [thread overview]
Message-ID: <1564573198-16219-1-git-send-email-wanpengli@tencent.com> (raw)
In-Reply-To: <1564572438-15518-3-git-send-email-wanpengli@tencent.com>
From: Wanpeng Li <wanpengli@tencent.com>
After commit d73eb57b80b (KVM: Boost vCPUs that are delivering interrupts), a
five years ago 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 reverting the kvm_arch_vcpu_runnable() condition
in kvm_vcpu_on_spin() loop and checking swait_active(&vcpu->wq) for
involuntary preemption.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Fixes: 98f4a1467 (KVM: add kvm_arch_vcpu_runnable() test to kvm_vcpu_on_spin() loop)
Cc: stable@vger.kernel.org
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
v1 -> v2:
* checking swait_active(&vcpu->wq) for involuntary preemption
virt/kvm/kvm_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ed061d8..12f2c91 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2506,7 +2506,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
continue;
if (vcpu == me)
continue;
- if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu))
+ if (READ_ONCE(vcpu->preempted) && swait_active(&vcpu->wq))
continue;
if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
!kvm_arch_vcpu_in_kernel(vcpu))
--
2.7.4
next prev parent reply other threads:[~2019-07-31 11:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-31 11:27 [PATCH 1/3] KVM: Don't need to wakeup vCPU twice afer timer fire Wanpeng Li
2019-07-31 11:27 ` [PATCH 2/3] KVM: Check preempted_in_kernel for involuntary preemption Wanpeng Li
2019-07-31 11:27 ` [PATCH 3/3] KVM: Fix leak vCPU's VMCS value into other pCPU Wanpeng Li
2019-07-31 11:39 ` Wanpeng Li [this message]
2019-07-31 12:55 ` [PATCH v2 " Paolo Bonzini
2019-08-01 3:35 ` Wanpeng Li
2019-07-31 12:56 ` [PATCH 1/3] KVM: Don't need to wakeup vCPU twice afer timer fire Paolo Bonzini
2019-07-31 13:14 ` Vitaly Kuznetsov
2019-07-31 16:39 ` Paolo Bonzini
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