On 16/3/18 8:31 am, Alex Williamson wrote: > A vfio ioeventfd will perform the pre-specified device write on > triggering of an eventfd. When coupled with KVM ioeventfds, this > feature allows a VM to trap a device page for virtualization, while > also registering targeted ioeventfds to maintain performance of high > frequency register writes within the trapped range. Much like the > existing interrupt eventfd/irqfd coupling, such writes can be handled > entirely in the host kernel. > > The new VFIO device ioctl may be supported by any vfio bus driver, > including mdev drivers, but the implementation here only enables > vfio-pci. This is intended as an acceleration path, bus drivers > may choose which regions to support and userspace should always > intend to fall back to non-accelerated handling when unavailable. > > v1->v2: > * Peter & Eric Sign-offs on 1/3 > * mutex_destroy() in 3/3 > * Slight enhancement to uapi description > * sparse clean - Sparse didn't like that we dropped the __iomem > address space when calling iowriteXX, re-adding it via the opaque > and data pointers of the virq was crude, and that was not a 32-bit > friendly soluion anyway, so add the iomem address to our ioeventfd > struct, pass that, and use a more simple, common handler. > > RFC->v1: > * An arbitrary limit is added for the number of ioeventfds supported > per device. The intention is to set this high enough to allow any > reasonable use case, but limit malicious user behavior. > * Split patches, including adding a patch for endian neutral io reads > and writes. This should be a nop for little-endian and avoid > redundant swap on big-endian, and hopefully resolves Alexey's > comments regarding the endian nature of this interface. > * Rebase to v4.16-rc3 > > Thanks, > Alex > > --- > > Alex Williamson (3): > vfio/pci: Pull BAR mapping setup from read-write path > vfio/pci: Use endian neutral helpers > vfio/pci: Add ioeventfd support > > > drivers/vfio/pci/vfio_pci.c | 35 +++++++ > drivers/vfio/pci/vfio_pci_private.h | 19 ++++ > drivers/vfio/pci/vfio_pci_rdwr.c | 184 +++++++++++++++++++++++++++++++---- > include/uapi/linux/vfio.h | 27 +++++ > 4 files changed, 245 insertions(+), 20 deletions(-) > LGTM, I gave it a try to make sure 2/3 does not break and it does not in all combinations of le/be host <=> le/be guest but I did not try the actual feature - cannot make up a test quickly... Reviewed-by: Alexey Kardashevskiy <aik@xxxxxxxxx> -- Alexey
