linux-kernel - Re: [PATCH v2 3/3] vfio/pci: Add ioeventfd support

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Date:   Fri, 16 Mar 2018 12:40:17 +0800
From:   Peter Xu <peterx@...hat.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, eric.auger@...hat.com, aik@...abs.ru
Subject: Re: [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 <alex.williamson@...hat.com>

Reviewed-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu