On Mon, Oct 31, 2022 at 11:45:55AM -0400, Michael S. Tsirkin wrote: > On Thu, Oct 27, 2022 at 05:27:28PM -0400, Stefan Hajnoczi wrote: > > On Fri, Oct 07, 2022 at 05:56:42PM +0100, Usama Arif wrote: > > > This includes the additions to the corresponding device and driver > > > conformances. > > > > > > Signed-off-by: Usama Arif <[email protected]> > > > Signed-off-by: Stefan Hajnoczi <[email protected]> > > > > You can keep this. One thought: > > > > I realized that virtio-mmio support won't be very useful until > > virtio-mmio gets MSI-X support because drivers currently cannot > > differentiate between device auxiliary notifications. > > > > Stefan > > > The big issue with MSI is it actually needs a ton of registers > for interrupt rebalancing, masking etc and they need to be fast. > Maybe a status bit like pci has makes sense here.
This patch does add an ISR bit:
diff --git a/content.tex b/content.tex
index 33362b7..8968fcd 100644
--- a/content.tex
+++ b/content.tex
@@ -2049,6 +2049,8 @@ \subsection{MMIO Device Register Layout}\label{sec:Virtio
Transport Options / Vi
in at least one of the active virtual queues.
\item [Configuration Change Notification] - bit 1 - the interrupt was
asserted because the configuration of the device has changed.
+ \item [Device-specific Driver Auxiliary Notification] - bit 2 - the
interrupt was
+ asserted because a device-specific event occurred to notify the driver.
The problem is that the driver doesn't know which device-specific event
occurred, so the mechanism is less useful than the MSI-X approach where
the driver knows exactly which (of potentially many) device-specific
events occurred.
Stefan
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