Re: [PATCH v3 4/9] xen/grant-table: Allow allocating buffers suitable for DMA

Boris Ostrovsky
2018-06-13T01:12:34Z

On 06/12/2018 09:41 AM, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>
> Extend grant table module API to allow allocating buffers that can
> be used for DMA operations and mapping foreign grant references
> on top of those.
> The resulting buffer is similar to the one allocated by the balloon
> driver in terms that proper memory reservation is made
> ({increase|decrease}_reservation and VA mappings updated if needed).
> This is useful for sharing foreign buffers with HW drivers which
> cannot work with scattered buffers provided by the balloon driver,
> but require DMAable memory instead.
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

with a small nit below

> ---
> drivers/xen/Kconfig | 13 ++++++
> drivers/xen/grant-table.c | 97 +++++++++++++++++++++++++++++++++++++++
> include/xen/grant_table.h | 18 ++++++++
> 3 files changed, 128 insertions(+)
>
> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> index e5d0c28372ea..39536ddfbce4 100644
> --- a/drivers/xen/Kconfig
> +++ b/drivers/xen/Kconfig
> @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC
> to other domains. This can be used to implement frontend drivers
> or as part of an inter-domain shared memory channel.
>
> +config XEN_GRANT_DMA_ALLOC
> + bool "Allow allocating DMA capable buffers with grant reference module"
> + depends on XEN && HAS_DMA
> + help
> + Extends grant table module API to allow allocating DMA capable
> + buffers and mapping foreign grant references on top of it.
> + The resulting buffer is similar to one allocated by the balloon
> + driver in terms that proper memory reservation is made
> + ({increase|decrease}_reservation and VA mappings updated if needed).

I think you should drop the word "terms" and say "is made *by*" and "VA
mappings *are* updated"

And similar change in the commit message.

-boris