From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [PATCH V2 2/6] kvm: detect assigned device via irqbypass manager Date: Fri, 17 Jul 2020 12:08:21 -0600 Message-ID: <20200717120821.3c2a56db@x1.home> References: <1594898629-18790-1-git-send-email-lingshan.zhu@intel.com> <1594898629-18790-3-git-send-email-lingshan.zhu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1594898629-18790-3-git-send-email-lingshan.zhu@intel.com> Sender: netdev-owner@vger.kernel.org To: Zhu Lingshan Cc: mst@redhat.com, pbonzini@redhat.com, sean.j.christopherson@intel.com, wanpengli@tencent.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org On Thu, 16 Jul 2020 19:23:45 +0800 Zhu Lingshan wrote: > vDPA devices has dedicated backed hardware like > passthrough-ed devices. Then it is possible to setup irq > offloading to vCPU for vDPA devices. Thus this patch tries to > manipulated assigned device counters via irqbypass manager. > > We will increase/decrease the assigned device counter in kvm/x86. > Both vDPA and VFIO would go through this code path. > > This code path only affect x86 for now. > > Signed-off-by: Zhu Lingshan > Suggested-by: Jason Wang > --- > arch/x86/kvm/x86.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 00c88c2..20c07d3 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -10624,11 +10624,17 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons, > { > struct kvm_kernel_irqfd *irqfd = > container_of(cons, struct kvm_kernel_irqfd, consumer); > + int ret; > > irqfd->producer = prod; > + kvm_arch_start_assignment(irqfd->kvm); > + ret = kvm_x86_ops.update_pi_irte(irqfd->kvm, > + prod->irq, irqfd->gsi, 1); > + > + if (ret) > + kvm_arch_end_assignment(irqfd->kvm); > > - return kvm_x86_ops.update_pi_irte(irqfd->kvm, > - prod->irq, irqfd->gsi, 1); > + return ret; > } > > void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons, Why isn't there a matching end-assignment in the del_producer path? It seems this only goes one-way, what happens when a device is hot-unplugged from the VM or the device interrupt configuration changes. This will still break vfio if it's not guaranteed to be symmetric. Thanks, Alex