On Wed, 2021-07-07 at 11:41 -0400, Peter Xu wrote:
> The parameters of intel-iommu device are non-trivial to understand. Add an
> entry for it so that people can reference to it when using.
>
> There're actually a few more options there, but I hide them explicitly because
> they shouldn't be used by normal QEMU users.
>
> Cc: Chao Yang <chay...@redhat.com>
> Cc: Lei Yang <leiy...@redhat.com>
> Cc: Jing Zhao <jinz...@redhat.com>
> Cc: Jason Wang <jasow...@redhat.com>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Cc: Alex Williamson <alex.william...@redhat.com>
> Reviewed-by: Jason Wang <jasow...@redhat.com>
> Reviewed-by: Yi Liu <yi.l....@intel.com>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> v2:
> - Drop "in the guest" in intremap entry [Jason]
> - Explain how the default value of intremap is chosen [Eric]
> - Add r-bs for Jason and Yi
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> qemu-options.hx | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 8965dabc83..0fcc8973dd 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -926,6 +926,39 @@ SRST
>
> ``-device pci-ipmi-bt,bmc=id``
> Like the KCS interface, but defines a BT interface on the PCI bus.
> +
> +``-device intel-iommu[,option=...]``
> + This is only supported by ``-machine q35``, which will enable Intel VT-d
> + emulation within the guest. It supports below options:
> +
> + ``intremap=on|off`` (default: auto)
> + This enables interrupt remapping feature. It's required to enable
> + complete x2apic. Currently it only supports kvm kernel-irqchip modes
> + ``off`` or ``split``, while full kernel-irqchip is not yet supported.
> + The default value is "auto", which will be decided by the mode of
> + kernel-irqchip.
> +
> + ``caching-mode=on|off`` (default: off)
> + This enables caching mode for the VT-d emulated device. When
> + caching-mode is enabled, each guest DMA buffer mapping will generate
> an
> + IOTLB invalidation from the guest IOMMU driver to the vIOMMU device
> in
> + a synchronous way. It is required for ``-device vfio-pci`` to work
> + with the VT-d device, because host assigned devices requires to setup
> + the DMA mapping on the host before guest DMA starts.
> +
> + ``device-iotlb=on|off`` (default: off)
> + This enables device-iotlb capability for the emulated VT-d device.
> So
> + far virtio/vhost should be the only real user for this parameter,
> + paired with ats=on configured for the device.
> +
> + ``aw-bits=39|48`` (default: 39)
> + This decides the address width of IOVA address space. The address
> + space has 39 bits width for 3-level IOMMU page tables, and 48 bits
> for
> + 4-level IOMMU page tables.
> +
> + Please also refer to the wiki page for general scenarios of VT-d
> + emulation in QEMU: https://wiki.qemu.org/Features/VT-d.
> +
> ERST
>
> DEF("name", HAS_ARG, QEMU_OPTION_name,
As far as I know this looks very good.
Thanks for doing this!
Reviewed-by: Maxim Levitsky <mlevi...@redhat.com>
Best regards,
Maxim Levitsky
