Hello! > Yes, I think it makes sense to just pick the low-hanging fruit for > virtio-mmio and wait for pci.
Does this mean that my series can be accepted as it is? Since PCI is potentially better solution, MMIO is a low priority in my project, and i have lots of other tasks. This means i unfortunately don't have time for further refactor. If you ACK, i will resend the series once again as v3, i set up git send-email and it should be working now. I just wanted to share this piece because it's already done, and i would not like it to go to oblivion again. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia > -----Original Message----- > From: qemu-devel-bounces+p.fedin=samsung....@nongnu.org [mailto:qemu-devel- > bounces+p.fedin=samsung....@nongnu.org] On Behalf Of Cornelia Huck > Sent: Friday, May 08, 2015 1:20 PM > To: Pavel Fedin > Cc: qemu-devel@nongnu.org > Subject: Re: [Qemu-devel] [PATCH v2 2/3] virtio-mmio: introduce > set_guest_notifiers > > On Fri, 08 May 2015 09:45:00 +0300 > Pavel Fedin <p.fe...@samsung.com> wrote: > > > Hello! > > > > > Hm, weren't there some patches for irqfd on arm? > > > > Yes, there were. However, they had a design problem by breaking backwards compatibility > > with unmodified virtio. Their idea was to set up one more shared memory > > area between > > virtio and vhost-net and use it to pass ISR value, which helps to > > distinguish, which event > > took place (queue update or config change). So, this idea was rejected. > > http://lists.gnu.org/archive/html/qemu-devel/2014-10/msg03056.html > > > > I thought about it, and technically, i think, this can be done in better > > way. Actually, > > as far as i understood, all we need is mechanism for distinguishing between > > these two > > events. On PCI we do this by using multiple IRQs via MSI-X, and one IRQ > > signals exactly > > one type of event. MSI-X code also has "two IRQs" mode as a failsafe, where > > one IRQ > > signals config change and another IRQ signals queues update (and all queues > > are polled in > > turn). I think a similar thing could be done for virtio-mmio. It could > > allocate two IRQs > > instead of one and describe both of them in the device tree. Guest side, > > upon seeing that, > > could make use of those two IRQs and acknowledge to the host side that > > "yes, i am new > > version and use new mode". > > But, sorry, i will unlikely implement this, because we already have PCI > > with MSI-X (i > > hope this is going to be published soon), so my project can use PCI > > emulation. So > > implementing irqfds for virtio-mmio is a bit out of my scope. > > Thanks for the explanation. >
