On Wed, Aug 27, 2025 at 06:21:28AM -0400, Michael S. Tsirkin wrote: > On Tue, Aug 26, 2025 at 06:52:11PM +0000, Parav Pandit wrote: > > > > > If it does not, and a user pull out the working device, how does > > > > > your patch help? > > > > > > > > > A driver must tell that it will not follow broken ancient behaviour and > > > > at that > > > point device would stop its ancient backward compatibility mode. > > > > > > > > > > > > I don't know what is "ancient backward compatibility mode". > > > > > Let me explain. > > Sadly, CSPs virtio pci device implementation is done such a way that, it > > works with ancient Linux kernel which does not have commit 43bb40c5b9265. > > > OK we are getting new information here. > > So let me summarize. There's a virtual system that pretends, to the > guest, that device was removed by surprise removal, but actually > device is there and is still doing DMA. > Is that a fair summary?
If that is the case, the thing to do would be to try and detect the fake removal and then work with device as usual - device not doing DMA after removal is pretty fundamental, after all. For example, how about reading device control+status? If we get all ones device has been removed If we get 0 in bus master: device has been removed but re-inserted Anything else is a fake removal Hmm? > -- > MST
