From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH 1/3] vfio-ccw: add capabilities chain Date: Fri, 21 Dec 2018 12:12:02 +0100 Message-ID: <20181221121202.2fefa757.cohuck@redhat.com> References: <20181122165432.4437-1-cohuck@redhat.com> <20181122165432.4437-2-cohuck@redhat.com> <20181218182400.6305b061.cohuck@redhat.com> <20181219092800.654fcc21@x1.home> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-s390@vger.kernel.org, Eric Farman , Pierre Morel , kvm@vger.kernel.org, Farhan Ali , qemu-devel@nongnu.org, Halil Pasic , qemu-s390x@nongnu.org To: Alex Williamson Return-path: In-Reply-To: <20181219092800.654fcc21@x1.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On Wed, 19 Dec 2018 09:28:00 -0700 Alex Williamson wrote: > On Tue, 18 Dec 2018 18:24:00 +0100 > Cornelia Huck wrote: > > > On Mon, 17 Dec 2018 16:53:34 -0500 > > Eric Farman wrote: > > > > > On 11/22/2018 11:54 AM, Cornelia Huck wrote: > > > > > > ...snip... > > > > > > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > > > > index 813102810f53..565669f95534 100644 > > > > --- a/include/uapi/linux/vfio.h > > > > +++ b/include/uapi/linux/vfio.h > > > > @@ -297,6 +297,7 @@ struct vfio_region_info_cap_type { > > > > > > > > #define VFIO_REGION_TYPE_PCI_VENDOR_TYPE (1 << 31) > > > > #define VFIO_REGION_TYPE_PCI_VENDOR_MASK (0xffff) > > > > +#define VFIO_REGION_TYPE_CCW (1 << 30) > > > > > > Oof. So the existing VFIO_REGION_TYPE_PCI_VENDOR_TYPE gets OR'd with > > > another value (e.g., 8086). But in 4.20, there was a > > > VFIO_REGION_TYPE_GFX is added as simply "1" ... Which direction are > > > these definitions being added from? I guess asked another way, is > > > _TYPE_CCW going to be OR'd with anything else that necessitates its > > > presence as an identifier with some Other Thing, or should this follow > > > the TYPE_GFX enumeration? Perhaps the type field needs to be tidied up > > > to help this sit more cleanly now? (Sorry!) > > > > The semantics of that type stuff are really a bit unclear to me :( > > > > I don't think we'll ever do any fancy mask handling for ccw. It is > > probably enough to have any kind of uniqueness within the different > > types, so maybe counting up would be indeed enough... > > Just to confirm, this is the intended usage, simply reserve a new type > following the GFX region example. We can define VFIO_REGION_TYPE_CCW > as 2 and then there's a whole address space of sub-types to fill in > within that. I might have over-engineered PCI a bit with the address > space split, but it seemed like a good idea at the time to pre-define a > type address space for each vendor, such that they only need to define > the sub-types and we can avoid namespace collisions. Unfortunately > this implicit definition for each PCI vendor also contributes to the > confusion here. Sorry. Thanks, > > Alex Thanks for the explanation. I'm simply switching VFIO_REGION_TYPE_CCW to 2 in the next version.