Re: [Xen-devel] [PATCH v6 7/7] xen/arm: export shared memory regions as reserved-memory on device tree

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 31/07/18 19:23, Stefano Stabellini wrote:
> Shared memory regions need to be advertised to the guest. Fortunately, a
> device tree binding for special memory regions already exist:
> reserved-memory.
>
> Add a reserved-memory node for each shared memory region, for both
> masters and slaves.
>
> Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
> ---
>   tools/libxl/libxl_arch.h |  2 +-
>   tools/libxl/libxl_arm.c  | 52 +++++++++++++++++++++++++++++++++++++++++++++---
>   tools/libxl/libxl_dom.c  |  2 +-
>   tools/libxl/libxl_x86.c  |  2 +-
>   4 files changed, 52 insertions(+), 6 deletions(-)
>
> diff --git a/tools/libxl/libxl_arch.h b/tools/libxl/libxl_arch.h
> index 6a07ccf..3626e4a 100644
> --- a/tools/libxl/libxl_arch.h
> +++ b/tools/libxl/libxl_arch.h
> @@ -36,7 +36,7 @@ int libxl__arch_domain_create(libxl__gc *gc, 
> libxl_domain_config *d_config,
>   /* setup arch specific hardware description, i.e. DTB on ARM */
>   _hidden
>   int libxl__arch_domain_init_hw_description(libxl__gc *gc,
> -                                           libxl_domain_build_info *info,
> +                                           libxl_domain_config *d_config,
>                                              libxl__domain_build_state *state,
>                                              struct xc_dom_image *dom);
>   /* finalize arch specific hardware description. */
> diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
> index 5f62e78..4020453 100644
> --- a/tools/libxl/libxl_arm.c
> +++ b/tools/libxl/libxl_arm.c
> @@ -461,6 +461,49 @@ static int make_memory_nodes(libxl__gc *gc, void *fdt,
>       return 0;
>   }
>   
> +static int make_reserved_nodes(libxl__gc *gc, void *fdt,
> +                               libxl_domain_config *d_config)
> +{
> +    int res, i;
> +    const char *name;
> +
> +    if (d_config->num_sshms == 0)
> +        return 0;
> +
> +    res = fdt_begin_node(fdt, "reserved-memory");
> +    if (res) return res;
> +
> +    res = fdt_property_cell(fdt, "#address-cells", ROOT_ADDRESS_CELLS);
> +    if (res) return res;
> +
> +    res = fdt_property_cell(fdt, "#size-cells", ROOT_SIZE_CELLS);
> +    if (res) return res;
> +
> +    res = fdt_property(fdt, "ranges", NULL, 0);
> +    if (res) return res;
> +
> +    for (i = 0; i < d_config->num_sshms; i++) {
> +        uint64_t start = d_config->sshms[i].begin;
> +        if (d_config->sshms[i].role == LIBXL_SSHM_ROLE_SLAVE)
> +            start += d_config->sshms[i].offset;
> +        name = GCSPRINTF("memory@%"PRIx64, start);
I understand the node will be useful for avoid the guest using as a 
normal memory. We also need to make sure the guest can detect what it is 
used for (imagine a driver for it). So you probably want a need 
compatible and more information in it.
Also, this would be clearer if the name is called xen-shmem@ rather than 
memory@.
> +
> +        res = fdt_begin_node(fdt, name);
> +        if (res) return res;
> +
> +        res = fdt_property_regs(gc, fdt, ROOT_ADDRESS_CELLS, ROOT_SIZE_CELLS,
> +                                1, start, d_config->sshms[i].size);
> +
> +        res = fdt_end_node(fdt);
> +        if (res) return res;
> +    }
> +
> +    res = fdt_end_node(fdt);
> +    if (res) return res;
> +
> +    return 0;
> +}
> +
Cheers,

--
Julien Grall

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