Re: [libvirt] [PATCH v2 1/2] vfio/mdev: add version attribute for mdev device

On Tue, May 14, 2019 at 03:43:44PM +0800, Erik Skultety wrote: > On Tue, May 14, 2019 at 03:32:19AM -0400, Yan Zhao wrote: > > On Tue, May 14, 2019 at 03:20:40PM +0800, Erik Skultety wrote:

> > > That said, from libvirt POV as a consumer, I'd expect there to be truly only 2 > > > errors (I believe Alex has mentioned something similar in one of his responses > > > in one of the threads): > > > a) read error indicating that an mdev type doesn't support migration > > > - I assume if one type doesn't support migration, none of the other > > > types exposed on the parent device do, is that a fair assumption?

> > > b) write error indicating that the mdev types are incompatible for > > > migration > > > > > > Regards, > > > Erik > > Thanks for this explanation. > > so, can we arrive at below agreements? > > > > 1. "not to define the specific errno returned for a specific situation, > > let the vendor driver decide, userspace simply needs to know that an errno on > > read indicates the device does not support migration version comparison and > > that an errno on write indicates the devices are incompatible or the target > > doesn't support migration versions. " > > 2. vendor driver should log detailed error reasons in kernel log. > > That would be my take on this, yes, but I open to hear any other suggestions and > ideas I couldn't think of as well.

> > Erik got it. thanks a lot! hi Cornelia and Dave, do you also agree on: 1. "not to define the specific errno returned for a specific situation, let the vendor driver decide, userspace simply needs to know that an errno on read indicates the device does not support migration version comparison and that an errno on write indicates the devices are incompatible or the target doesn't support migration versions. " 2. vendor driver should log detailed error reasons in kernel log.