From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v3 44/59] KVM: arm/arm64: GICv4: Handle MOVI applied to a VLPI Date: Wed, 30 Aug 2017 22:04:58 +0200 Message-ID: <20170830200458.GK24522@cbox> References: <20170731172637.29355-1-marc.zyngier@arm.com> <20170731172637.29355-45-marc.zyngier@arm.com> <20170828181817.GE24649@cbox> <954a7441-c91e-5d1b-98b7-2978291c5259@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Jason Cooper , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Gleixner , kvmarm@lists.cs.columbia.edu To: Marc Zyngier Return-path: Content-Disposition: inline In-Reply-To: <954a7441-c91e-5d1b-98b7-2978291c5259@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Wed, Aug 30, 2017 at 03:08:01PM +0100, Marc Zyngier wrote: > On 28/08/17 19:18, Christoffer Dall wrote: > > On Mon, Jul 31, 2017 at 06:26:22PM +0100, Marc Zyngier wrote: > >> When the guest issues a MOVI, we need to tell the physical ITS > >> that we're now targetting a new vcpu. This is done by extracting > >> the current mapping, updating the target, and reapplying the > >> mapping. The core ITS code should do the right thing. > >> > >> Signed-off-by: Marc Zyngier > >> --- > >> virt/kvm/arm/vgic/vgic-its.c | 13 +++++++++++++ > >> 1 file changed, 13 insertions(+) > >> > >> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c > >> index 79bac93d3e7d..aaad577ce328 100644 > >> --- a/virt/kvm/arm/vgic/vgic-its.c > >> +++ b/virt/kvm/arm/vgic/vgic-its.c > >> @@ -706,6 +706,19 @@ static int vgic_its_cmd_handle_movi(struct kvm *kvm, struct vgic_its *its, > >> ite->irq->target_vcpu = vcpu; > >> spin_unlock(&ite->irq->irq_lock); > >> > >> + if (ite->irq->hw) { > >> + struct its_vlpi_map map; > >> + int ret; > >> + > >> + ret = its_get_vlpi(ite->irq->host_irq, &map); > >> + if (ret) > >> + return ret; > >> + > >> + map.vpe_idx = vcpu->vcpu_id; > >> + > >> + return its_map_vlpi(ite->irq->host_irq, &map); > > > > Since you're not holding the irq_lock across these two calls, would it > > be possible that the forwarding was removed through some other call path > > here, and could you end up passing an invalid host_irq to its_map_vlpi? > I believe we should be OK here, as we hold the ITS mutex during any > command processing, and both the forward/unforward paths take that same > mutex. ok, yes, as long as the only other modifirs are the forward/unforward paths and they hold the mutex, we should be fine. > > On a slightly different note, it looks like the MOVI code could benefit > from using vgic_its_resolve_lpi(), which has been introduce earlier in > this series. Only problem is you'd need to get a handle to the ite as well to change the collection pointer. I suppose you could add another pointer pointer. -Christoffer