Messages in this thread | | | Date | Thu, 4 Jul 2013 07:25:23 -0700 | From | Guenter Roeck <> | Subject | Re: [RFC PATCH] uio: uio_pci_generic: Add support for MSI interrupts |
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On Thu, Jul 04, 2013 at 10:20:23AM +0300, Michael S. Tsirkin wrote: > On Thu, Jun 27, 2013 at 10:00:52AM -0700, Guenter Roeck wrote: > > On Thu, Jun 27, 2013 at 10:45:01AM +0300, Michael S. Tsirkin wrote: > > > On Wed, Jun 26, 2013 at 03:30:23PM -0700, Guenter Roeck wrote: > > > > Enable support for MSI interrupts if the device supports it. > > > > Since MSI interrupts are edge triggered, it is no longer necessary to > > > > disable interrupts in the kernel and re-enable them from user-space. > > > > Instead, clearing the interrupt condition in the user space application > > > > automatically re-enables the interrupt. > > > > > > > > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > > > > --- > > > > An open question is if we can just do this unconditionally > > > > or if there should be some flag to enable it. A module parameter, maybe ? > > > > > > NACK > > > > > > UIO is for devices that don't do memory writes. > > > Anything that can do writes must be protected by an IOMMU > > > and/or have a secure kernel driver, not a UIO stub. > > > > > > MSI is done by memory writes so if userspace > > > controls the device it can trick it to write > > > anywhere in memory. > > > > > Just out of curiosity: Since MSI support is mandatory for all PCIE devices, > > isn't that possible anyway, even if MSI is not enabled by the kernel ? > > All one would need to do is to enable MSI from user space; after all, > > the chip configuration space is writable. > > > > Thanks, > > Guenter > > If a device has capability to do writes, sure. So don't do this then :) > Not an option. I need to use MSI.
Not that it matters anymore - turns out it was better writing a specific driver for my devices anyway; I needed to be able to disable chip interrupts before unloading the driver. But why is it then a reason to NACK this patch ? Besides, doesn't one have to be root anyway to perform such activities, which could then be more easily accomplished by writing into /dev/mem ?
Thanks, Guenter
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