On Thursday 07 May 2009, Gregory Haskins wrote: > I guess technically mmio can just be a simple access of the page which > would be problematic to trap locally without a PF. However it seems > that most mmio always passes through a ioread()/iowrite() call so this > is perhaps the hook point. If we set the stake in the ground that mmios > that go through some other mechanism like PFs can just hit the "slow > path" are an acceptable casualty, I think we can make that work. > > Thoughts? An mmio that goes through a PF is a bug, it's certainly broken on a number of platforms, so performance should not be an issue there. Note that are four commonly used interface classes for PIO/MMIO: 1. readl/writel: little-endian MMIO 2. inl/outl: little-endian PIO 3. ioread32/iowrite32: converged little-endian PIO/MMIO 4. __raw_readl/__raw_writel: native-endian MMIO without checks You don't need to worry about the __raw_* stuff, as this should never be used in device drivers. As a simplification, you could mandate that all drivers that want to use this get converted to the ioread/iowrite class of interfaces and leave the others slow. Arnd <>< -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
