On Thu, Oct 12, 2023 at 11:11:20AM +0000, Parav Pandit wrote: > > > From: Michael S. Tsirkin <mst@xxxxxxxxxx> > > Sent: Thursday, October 12, 2023 4:23 PM > > > > On Tue, Sep 26, 2023 at 03:45:36AM +0000, Parav Pandit wrote: > > > > > > > > > > From: Michael S. Tsirkin <mst@xxxxxxxxxx> > > > > Sent: Tuesday, September 26, 2023 12:06 AM > > > > > > > One can thinkably do that wait in hardware, though. Just defer > > > > completion until read is done. > > > > > > > Once OASIS does such new interface and if some hw vendor _actually_ wants > > to do such complex hw, may be vfio driver can adopt to it. > > > > The reset behaviour I describe is already in the spec. What else do you want > > OASIS to standardize? Virtio currently is just a register map it does not yet > > include suggestions on how exactly do pci express transactions look. You feel we > > should add that? > > The reset behavior in the spec for modern as listed in [1] and [2] is just fine. > > What I meant is in context of having MMIO based legacy registers to "defer completion until read is done". > I think you meant, "Just differ read completion, until reset is done". yes > This means the hw needs to finish the device reset for thousands of devices within the read completion timeout of the pci. no, each device does it's own reset. > So when if OASIS does such standardization, someone can implement it. > > What I recollect, is OASIS didn't not standardize such anti-scale approach and took the admin command approach which achieve better scale. > Hope I clarified. You are talking about the extension for trap and emulate. I am instead talking about devices that work with existing legacy linux drivers with no traps. > I am not expecting OASIS to do anything extra for legacy registers. > > [1] The device MUST reset when 0 is written to device_status, and present a 0 in device_status once that is done. > [2] After writing 0 to device_status, the driver MUST wait for a read of device_status to return 0 before reinitializing > the device. We can add a note explaining that legacy drivers do not wait after doing reset, that is not a problem. If someone wants to make a device that works with existing legacy linux drivers, they can do that. Won't work with all drivers though, which is why oasis did not want to standardize this. -- MST
