On Mon, 21 Feb 2011, KY Srinivasan wrote: > > > Like most virtualization platforms, Hyper-V also emulates the full PC > > > platform. So, it is possible that the driver of some other emulated > > > devices might register for the IRQ line we might have selected. That > > > is the race this code addresses. For performance reasons, we want > > > both storage and network traffic to go over the PV drivers. > > > > So in case your driver gets the interrupt line first, which the other > > driver wants to acquire as well, then what? Do you want to do that > > probe magic in the other driver as well? What if this is a regular > > device driver which gets its irq number from ACPI/PCI or > > whatever. Then that driver simply wont work as it's interrupt line is > > busy. > > > > > > > > > > I don't know why the previous reviewer wanted to have that > > > > dynamic. That just does not make sense to me. > > > > > > Prior to this patch, we had a hard coded interrupt line for use by > > > this driver. If that line was already in use, the load of this driver > > > would fail. This would be a fatal issue especially for distributions > > > that have embedded these PV drivers as part of their installation > > > media. This patch deals with such collisions in a more graceful way - > > > we would not bail until we have scanned all low interrupt lines. > > > > So you trade breaking the PV stuff against breaking random other > > drivers? That doesn't sound like a brilliant idea. > > > > There are various ways to solve that proper. > > > > - You can provide the interrupt number from ACPI/PCI or whatever your HV > > provides as enumeration. > > > > - Use a fixed vector like XEN does for the event channel > > > > - Use dynamic allocation in the IOAPIC space like the kernel does for > > MSI(-X) > > > > Thanks, > > > > tglx > > I am not claiming that what I have done here is the best possible solution. > However, I will submit to you that it is better than what we had here > prior to this patch. I will address this and a whole lot of other issues > in future patches. No, it's _NOT_ better in any way. You trade breaking your PV thing against breaking random other drivers. Care to explain why you think that's better ? Thanks, tglx _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
