From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Farman Subject: Re: [PATCH 1/3] vfio-ccw: add capabilities chain Date: Tue, 18 Dec 2018 12:56:08 -0500 Message-ID: References: <20181122165432.4437-1-cohuck@redhat.com> <20181122165432.4437-2-cohuck@redhat.com> <20181218182400.6305b061.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181218182400.6305b061.cohuck@redhat.com> Content-Language: en-US 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-Archive: List-Post: To: Cornelia Huck Cc: linux-s390@vger.kernel.org, Alex Williamson , Pierre Morel , kvm@vger.kernel.org, Farhan Ali , qemu-devel@nongnu.org, Halil Pasic , qemu-s390x@nongnu.org List-ID: On 12/18/2018 12:24 PM, 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 :( +1 I was confused when I first looked at this. When I applied it to 4.20, I got another level of confusion. ;) > > 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... Considering the subtype space, I think it would be fine too. But wanted to ask in case I've been out of the loop on something. > >> >> - Eric >> >>> >>> /* 8086 Vendor sub-types */ >>> #define VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION (1) >>> >> >