From: Neo Jia [mailto:address@hidden
Sent: Thursday, September 29, 2016 3:23 AM
On Thu, Sep 22, 2016 at 03:26:38PM +0100, Daniel P. Berrange wrote:
On Thu, Sep 22, 2016 at 08:19:21AM -0600, Alex Williamson wrote:
On Thu, 22 Sep 2016 09:41:20 +0530
Kirti Wankhede <address@hidden> wrote:
My concern is that a type id seems arbitrary but we're specifying that
it be unique. We already have something unique, the name. So why try
to make the type id unique as well? A vendor can accidentally create
their vendor driver so that a given name means something very
specific. On the other hand they need to be extremely deliberate to
coordinate that a type id means a unique thing across all their product
lines.
Let me clarify, type id should be unique in the list of
mdev_supported_types. You can't have 2 directories in with same name.
Of course, but does that mean it's only unique to the machine I'm
currently running on? Let's say I have a Tesla P100 on my system and
type-id 11 is named "GRID-M60-0B". At some point in the future I
replace the Tesla P100 with a Q1000 (made up). Is type-id 11 on that
new card still going to be a "GRID-M60-0B"? If not then we've based
our XML on the wrong attribute. If the new device does not support
"GRID-M60-0B" then we should generate an error, not simply initialize
whatever type-id 11 happens to be on this new card.
If there are 2 M60 in the system then you would find '11' type directory
in mdev_supported_types of both M60. If you have P100, '11' type would
not be there in its mdev_supported_types, it will have different types.
For example, if you replace M60 with P100, but XML is not updated. XML
have type '11'. When libvirt would try to create mdev device, libvirt
would have to find 'create' file in sysfs in following directory format:
--- mdev_supported_types
|-- 11
| |-- create
but now for P100, '11' directory is not there, so libvirt should throw
error on not able to find '11' directory.
This really seems like an accident waiting to happen. What happens
when the user replaces their M60 with an Intel XYZ device that happens
to expose a type 11 mdev class gpu device? How is libvirt supposed to
know that the XML used to refer to a GRID-M60-0B and now it's an
INTEL-IGD-XYZ? Doesn't basing the XML entry on the name and removing
yet another arbitrary requirement that we have some sort of globally
unique type-id database make a lot of sense? The same issue applies
for simple debug-ability, if I'm reviewing the XML for a domain and the
name is the primary index for the mdev device, I know what it is.
Seeing type-id='11' is meaningless.
Let me clarify again, type '11' is a string that vendor driver would
define (see my previous reply below) it could be "11" or "GRID-M60-0B".
If 2 vendors used same string we can't control that. right?
Lets remove 'id' from type id in XML if that is the concern. Supported
types is going to be defined by vendor driver, so let vendor driver
decide what to use for directory name and same should be used in device
xml file, it could be '11' or "GRID M60-0B":
<device>
<name>my-vgpu</name>
<parent>pci_0000_86_00_0</parent>
<capability type='mdev'>
<type='11'/>
...
</capability>
</device>
Then let's get rid of the 'name' attribute and let the sysfs directory
simply be the name. Then we can get rid of 'type' altogether so we
don't have this '11' vs 'GRID-M60-0B' issue. Thanks,
That sounds nice to me - we don't need two unique identifiers if
one will do.
Hi Alex and Daniel,
I just had some internal discussions here within NVIDIA and found out that
actually the name/label potentially might not be unique and the "id" will be.