Re: [Xen-devel] [PATCH v7 7/8] xen/arm: export shared memory regions as reserved-memory on device tree

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 28 Aug 2018, Julien Grall wrote:
> Hi,
> 
> On 11/08/18 01:00, 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>
> > ---
> > Changes in v7:
> > - change node name to xen-shmem
> > - add compatible property
> > - add id property
> > ---
> >   tools/libxl/libxl_arch.h |  2 +-
> >   tools/libxl/libxl_arm.c  | 59
> > +++++++++++++++++++++++++++++++++++++++++++++---
> >   tools/libxl/libxl_dom.c  |  2 +-
> >   tools/libxl/libxl_x86.c  |  2 +-
> >   4 files changed, 59 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..72dd0d2 100644
> > --- a/tools/libxl/libxl_arm.c
> > +++ b/tools/libxl/libxl_arm.c
> > @@ -461,6 +461,56 @@ 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;
> 
> NIT: newline.

I'll add

> > +        if (d_config->sshms[i].role == LIBXL_SSHM_ROLE_SLAVE)
> > +            start += d_config->sshms[i].offset;
> > +        name = GCSPRINTF("xen-shmem@%"PRIx64, start);
> > +
> > +        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);
> > +        if (res) return res;
> > +
> > +        res = fdt_property_compat(gc, fdt, 1, "xen,shared-memory");
> 
> This requires a patch in the Linux DT docs for the new binding. But more
> likely you want to expose a bit more about the shared-memory. For instance the
> ID is something really useful to have in hand.
> 
> This could help a tailored guest to distinguish between 2 shared memory.

yes, I'll do

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