From mboxrd@z Thu Jan 1 00:00:00 1970 From: Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [RFC v7 1/7] KVM: api: pass the devid in the msi routing entry Date: Thu, 21 Jul 2016 18:01:25 +0200 Message-ID: <20160721160124.GB32739@potion> References: <1468848357-2331-1-git-send-email-eric.auger@redhat.com> <1468848357-2331-2-git-send-email-eric.auger@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: eric.auger.pro@gmail.com, marc.zyngier@arm.com, christoffer.dall@linaro.org, andre.przywara@arm.com, drjones@redhat.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, pbonzini@redhat.com To: Eric Auger Return-path: Received: from mx1.redhat.com ([209.132.183.28]:46483 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753147AbcGUQBa (ORCPT ); Thu, 21 Jul 2016 12:01:30 -0400 Content-Disposition: inline In-Reply-To: <1468848357-2331-2-git-send-email-eric.auger@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 2016-07-18 13:25+0000, Eric Auger: > On ARM, the MSI msg (address and data) comes along with > out-of-band device ID information. The device ID encodes the > device that writes the MSI msg. Let's convey the device id in > kvm_irq_routing_msi and use KVM_MSI_VALID_DEVID flag value in > kvm_irq_routing_entry to indicate the msi devid is populated. > > Signed-off-by: Eric Auger > Reviewed-by: Andre Przywara > > --- > > v6 -> v7: > - Added Andre's R-b > > v4 -> v5: > - some rephrasing in api.txt according to Christoffer's comments > v2 -> v3: > - replace usage of KVM_IRQ_ROUTING_EXTENDED_MSI type by > usage of KVM_MSI_VALID_DEVID flag > - add note about KVM_CAP_MSI_DEVID capability > > v1 -> v2: > - devid id passed in kvm_irq_routing_msi instead of in > kvm_irq_routing_entry > > RFC -> PATCH > - remove kvm_irq_routing_extended_msi and use union instead > --- > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt > @@ -1479,9 +1483,20 @@ struct kvm_irq_routing_msi { > __u32 address_lo; > __u32 address_hi; > __u32 data; > - __u32 pad; > + union { > + __u32 pad; > + __u32 devid; > + }; > }; > > +devid: If KVM_MSI_VALID_DEVID is set, contains a unique device identifier > + for the device that wrote the MSI message. > + For PCI, this is usually a BFD identifier in the lower 16 bits. > + > +The per-VM KVM_CAP_MSI_DEVID capability advertises the requirement to > +provide the device ID. If this capability is not set, userland cannot > +rely on the kernel to allow the KVM_MSI_VALID_DEVID flag being set. It would be better to enforce this mentioned dependency on set KVM_CAP_MSI_DEVID, but is the dependency even required? It seems we were checking flags for zero, so KVM_MSI_VALID_DEVID couldn't have been set by old userspaces, therefor it is ok to only make it depend only on the presence of KVM_CAP_MSI_DEVID, like the patch does now. (I assume KVM_MSI_VALID_DEVID and KVM_CAP_MSI_DEVID are being merged at the same time.) Then there would be little point in having KVM_CAP_MSI_DEVID enableable, so does enabling KVM_CAP_MSI_DEVID mean that every MSI must have a valid devid? Thanks. --- I'm confused about the purpose behind two dynamic flags that seem to do that same thing, but those are just nitpicks, the API looks good in general.