linux-kernel - [PATCH CFT 0/4] VT-d PI fixes

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Date:   Tue,  6 Jun 2017 12:57:03 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Longpeng <longpeng2@...wei.com>,
        Huangweidong <weidong.huang@...wei.com>,
        Gonglei <arei.gonglei@...wei.com>,
        wangxin <wangxinxin.wang@...wei.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH CFT 0/4] VT-d PI fixes

These should fix, or at least help, the kernel panic reported by Longpeng
with VT-d posted interrupts.

CONFIG_DEBUG_LIST reports a double add, meaning that pi_pre_block ran twice
without pi_post_block deleting the vCPU from the blocked_on_vcpu list.
The only possibility that I could think of is that this:

        if (!kvm_arch_has_assigned_device(vcpu->kvm) ||
                !irq_remapping_cap(IRQ_POSTING_CAP)  ||
                !kvm_vcpu_apicv_active(vcpu))
                return;

was false in pi_post_block.  In turn, I can only think of hot-unplug as
the cause of this imbalance, but maybe there is another way to reach it
just via repeated startup and shutdown.  Gonglei reported problems with
hot-unplug offlist too, so this is a start.

In any case, patch 2 replaces it with a check on vcpu->pre_pcpu.
A similar change is done in patch 3 to vmx_vcpu_pi_load.  I don't
have hardware easily accessible with VT-d PI, so these patches are
compile-tested only.  I apologize for any stupid mistakes.

The first three patches are meant for stable versions too.

Paolo

Paolo Bonzini (4):
  KVM: VMX: extract __pi_post_block
  KVM: VMX: avoid double list add with VT-d posted interrupts
  KVM: VMX: simplify and fix vmx_vcpu_pi_load
  KVM: VMX: simplify cmpxchg of PI descriptor control field

 arch/x86/kvm/vmx.c | 228 ++++++++++++++++++++++++++---------------------------
 1 file changed, 110 insertions(+), 118 deletions(-)

-- 
2.13.0