[virtio-dev] Re: [PATCH V3 2/2] docs: vhost-user: Add Xen specific memory mapping support

["Alex Bennée" <alex.bennee@linaro.org>]

Viresh Kumar <viresh.kumar@linaro.org> writes:

> The current model of memory mapping at the back-end works fine where a
> standard call to mmap() (for the respective file descriptor) is enough
> before the front-end can start accessing the guest memory.
>
> There are other complex cases though where the back-end needs more
> information and simple mmap() isn't enough. For example Xen, a type-1
> hypervisor, currently supports memory mapping via two different methods,
> foreign-mapping (via /dev/privcmd) and grant-dev (via /dev/gntdev). In
> both these cases, the back-end needs to call mmap() and ioctl(), with
> extra information like the Xen domain-id of the guest whose memory we
> are trying to map.
>
> Add a new protocol feature, 'VHOST_USER_PROTOCOL_F_XEN_MMAP', which lets
> the back-end know about the additional memory mapping requirements.
> When this feature is negotiated, the front-end will send the additional
> information within the memory regions themselves.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

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