From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Alex Williamson <alex.williamson@redhat.com>, kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, qemu-devel@nongnu.org,
peterx@redhat.com, eric.auger@redhat.com
Subject: Re: [PATCH v2 0/3] vfio/pci: ioeventfd support
Date: Mon, 19 Mar 2018 20:09:04 +1100 [thread overview]
Message-ID: <28b02805-fa03-7f7c-b603-fa8985b305aa@ozlabs.ru> (raw)
In-Reply-To: <20180315212634.15150.88094.stgit@gimli.home>
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@ozlabs.ru>
--
Alexey
prev parent reply other threads:[~2018-03-19 9:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-15 21:31 [PATCH v2 0/3] vfio/pci: ioeventfd support Alex Williamson
2018-03-15 21:31 ` [PATCH v2 1/3] vfio/pci: Pull BAR mapping setup from read-write path Alex Williamson
2018-03-15 21:31 ` [PATCH v2 2/3] vfio/pci: Use endian neutral helpers Alex Williamson
2018-03-15 21:31 ` [PATCH v2 3/3] vfio/pci: Add ioeventfd support Alex Williamson
2018-03-16 4:40 ` Peter Xu
2018-03-19 9:09 ` Alexey Kardashevskiy [this message]
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