> From: Kirti Wankhede > Sent: Thursday, September 27, 2018 2:22 PM > > Generally a single instance of mdev device, a share of physical device, is > assigned to user space application or a VM. There are cases when multiple > instances of mdev devices of same or different types are required by User > space application or VM. For example in case of vGPU, multiple mdev > devices > of type which represents whole GPU can be assigned to one instance of > application or VM. > > All types of mdev devices may not support assigning multiple mdev devices > to a user space application. In that case vendor driver can fail open() > call of mdev device. But there is no way to know User space application > about the configuration supported by vendor driver. > > To expose supported configuration, vendor driver should add > 'multiple_mdev_support' attribute to type-id directory if vendor driver > supports assigning multiple mdev devices of a particular type-id to one > instance of user space application or a VM. > > User space application should read if 'multiple_mdev_support' attibute is > present in type-id directory of all mdev devices which are going to be > used. If all read 1 then user space application can proceed with multiple > mdev devices. > > This is optional and readonly attribute. I didn't get what is the exact problem from above description. Isn't it the basic point behind mdev concept that parent driver can create multiple mdev instances on a physical device? VFIO usually doesn't care whether multiple devices (pci or mdev) are assigned to same process/VM or not. Can you give some example of actual problem behind this change? Thanks Kevin > > Signed-off-by: Neo Jia <cjia@xxxxxxxxxx> > Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx> > --- > Documentation/ABI/testing/sysfs-bus-vfio-mdev | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/Documentation/ABI/testing/sysfs-bus-vfio-mdev > b/Documentation/ABI/testing/sysfs-bus-vfio-mdev > index 452dbe39270e..69e1291479ce 100644 > --- a/Documentation/ABI/testing/sysfs-bus-vfio-mdev > +++ b/Documentation/ABI/testing/sysfs-bus-vfio-mdev > @@ -85,6 +85,19 @@ Users: > a particular <type-id> that can help in understanding the > features provided by that type of mediated device. > > +What: /sys/.../mdev_supported_types/<type- > id>/multiple_mdev_support > +Date: September 2018 > +Contact: Kirti Wankhede <kwankhede@xxxxxxxxxx> > +Description: > + Reading this attribute will return 0 or 1. Returning 1 > indicates > + multiple mdev devices of a particular <type-id> assigned to > one > + User space application is supported by vendor driver. This is > + optional and readonly attribute. > +Users: > + Userspace applications interested in knowing if multiple > mdev > + devices of a particular <type-id> can be assigned to one > + instance of application. > + > What: /sys/.../<device>/<UUID>/ > Date: October 2016 > Contact: Kirti Wankhede <kwankhede@xxxxxxxxxx> > -- > 2.7.0
