Re: [PATCH v2 22/43] KVM: VMX: Drop unnecessary PI logic to handle impossible conditions
Paolo Bonzini <[email protected]>
| Newsgroups | org.kernel.vger.kvm-ppc,dev.linux.lists.kvmarm,org.infradead.lists.kvm-riscv,org.infradead.lists.linux-arm-kernel,org.infradead.lists.linux-riscv,org.kernel.vger.kvm,org.kernel.vger.linux-kernel,org.kernel.vger.linux-mips |
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| Message-ID | <[email protected]> |
On 09/10/21 04:12, Sean Christopherson wrote: > Drop sanity checks on the validity of the previous pCPU when handling > vCPU block/unlock for posted interrupts. Barring a code bug or memory > corruption, the sanity checks will never fire, and any code bug that does > trip the WARN is all but guaranteed to completely break posted interrupts, > i.e. should never get anywhere near production. > > This is the first of several steps toward eliminating kvm_vcpu.pre_cpu. > > Signed-off-by: Sean Christopherson <[email protected]> > --- > arch/x86/kvm/vmx/posted_intr.c | 24 ++++++++++-------------- > 1 file changed, 10 insertions(+), 14 deletions(-) The idea here is to avoid making things worse by not making the list inconsistent. But that's impossible to do if pre_pcpu goes away, so fair enough. Paolo > diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c > index 67cbe6ab8f66..6c2110d91b06 100644 > --- a/arch/x86/kvm/vmx/posted_intr.c > +++ b/arch/x86/kvm/vmx/posted_intr.c > @@ -118,12 +118,10 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) > } while (cmpxchg64(&pi_desc->control, old.control, > new.control) != old.control); > > - if (!WARN_ON_ONCE(vcpu->pre_pcpu = -1)) { > - spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > - list_del(&vcpu->blocked_vcpu_list); > - spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > - vcpu->pre_pcpu = -1; > - } > + spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > + list_del(&vcpu->blocked_vcpu_list); > + spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > + vcpu->pre_pcpu = -1; > } > > /* > @@ -153,14 +151,12 @@ int pi_pre_block(struct kvm_vcpu *vcpu) > > WARN_ON(irqs_disabled()); > local_irq_disable(); > - if (!WARN_ON_ONCE(vcpu->pre_pcpu != -1)) { > - vcpu->pre_pcpu = vcpu->cpu; > - spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > - list_add_tail(&vcpu->blocked_vcpu_list, > - &per_cpu(blocked_vcpu_on_cpu, > - vcpu->pre_pcpu)); > - spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > - } > + > + vcpu->pre_pcpu = vcpu->cpu; > + spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > + list_add_tail(&vcpu->blocked_vcpu_list, > + &per_cpu(blocked_vcpu_on_cpu, vcpu->pre_pcpu)); > + spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); > > WARN(pi_desc->sn = 1, > "Posted Interrupt Suppress Notification set before blocking"); >