Re: [PATCH v2 8/8] docs: Add '-device virtio-iommu' entry

From: Eric Auger <eric.auger@redhat.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: peter.maydell@linaro.org, ehabkost@redhat.com, mst@redhat.com,
	richard.henderson@linaro.org, qemu-devel@nongnu.org,
	shannon.zhaosl@gmail.com, qemu-arm@nongnu.org,
	pbonzini@redhat.com, imammedo@redhat.com
Subject: Re: [PATCH v2 8/8] docs: Add '-device virtio-iommu' entry
Date: Mon, 6 Sep 2021 16:41:23 +0200	[thread overview]
Message-ID: <4aaffa5a-e9cf-9997-aa59-dcb2726ad696@redhat.com> (raw)
In-Reply-To: <20210903143208.2434284-9-jean-philippe@linaro.org>

Hi Jean,

On 9/3/21 4:32 PM, Jean-Philippe Brucker wrote:
> Document the virtio-iommu device for qemu-system-x86_64. In particular
Nit: this is not only for qemu-system-x86_6. This also documents the
option usage for aarch64. Only the interrupt remapping note is x86-64
specific.

I think it also would be worth to mention the interaction with the
bypass iommu option as you mention "for all devices".

Thanks

Eric
> note the lack of interrupt remapping, which may be an important
> limitation on x86.
>
> Suggested-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>  qemu-options.hx | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 83aa59a920..9a1906a748 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -976,6 +976,9 @@ SRST
>      Please also refer to the wiki page for general scenarios of VT-d
>      emulation in QEMU: https://wiki.qemu.org/Features/VT-d.
>  
> +``-device virtio-iommu``
> +    Enable a paravirtual IOMMU, that manages DMA isolation and remapping
> +    for all PCI devices, but does not support interrupt remapping.
>  ERST
>  
>  DEF("name", HAS_ARG, QEMU_OPTION_name,