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SubjectRe: [PATCH v2 3/3] vfio/pci: Add ioeventfd support
On Thu, Mar 15, 2018 at 03:31:58PM -0600, Alex Williamson wrote:
> The ioeventfd here is actually irqfd handling of an ioeventfd such as
> supported in KVM. A user is able to pre-program a device write to
> occur when the eventfd triggers. This is yet another instance of
> eventfd-irqfd triggering between KVM and vfio. The impetus for this
> is high frequency writes to pages which are virtualized in QEMU.
> Enabling this near-direct write path for selected registers within
> the virtualized page can improve performance and reduce overhead.
> Specifically this is initially targeted at NVIDIA graphics cards where
> the driver issues a write to an MMIO register within a virtualized
> region in order to allow the MSI interrupt to re-trigger.
> Signed-off-by: Alex Williamson <>

Reviewed-by: Peter Xu <>

Peter Xu

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