Re: [RFC PATCH] libxl/arm: Insert "xen,dev-domid" property to virtio-mmio device node

[Oleksandr <olekstysh@xxxxxxxxx>]

On 19.04.22 00:47, Stefano Stabellini wrote:


Hello Stefano

> On Thu, 14 Apr 2022, Oleksandr Tyshchenko wrote:
> > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> >
> > This is needed for grant table based DMA ops layer (CONFIG_XEN_VIRTIO)
> > at the guest side to retrieve the ID of Xen domain where the corresponding
> > backend resides (it is used as an argument to the grant table APIs).
> >
> > This is a part of restricted memory access under Xen feature.
> >
> > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> I think this looks good overall.
thank you


>   Instead of mentioning details of the
> Linux implementation, we should mention the device tree binding instead,
> including a link to it. The device tree binding is the relevant spec in
> this case.
I got it, while new device tree binding is not approved yet, I should 
have inserted a link to the corresponding Linux commit.
https://lore.kernel.org/xen-devel/1649963973-22879-4-git-send-email-olekstysh@xxxxxxxxx/


> > ---
> > !!! This patch is based on non upstreamed yet “Virtio support for toolstack
> > on Arm” series which is on review now:
> > https://lore.kernel.org/xen-devel/1649442065-8332-1-git-send-email-olekstysh@xxxxxxxxx/
> >
> > All details are at:
> > https://lore.kernel.org/xen-devel/1649963973-22879-1-git-send-email-olekstysh@xxxxxxxxx/
> > ---
> >   tools/libs/light/libxl_arm.c | 14 ++++++++++++--
> >   1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
> > index 8132a47..d9b26fc 100644
> > --- a/tools/libs/light/libxl_arm.c
> > +++ b/tools/libs/light/libxl_arm.c
> > @@ -875,7 +875,8 @@ static int make_vpci_node(libxl__gc *gc, void *fdt,
> >   
> >   
> >   static int make_virtio_mmio_node(libxl__gc *gc, void *fdt,
> > -                                 uint64_t base, uint32_t irq)
> > +                                 uint64_t base, uint32_t irq,
> > +                                 uint32_t backend_domid)
> >   {
> >       int res;
> >       gic_interrupt intr;
> > @@ -900,6 +901,14 @@ static int make_virtio_mmio_node(libxl__gc *gc, void *fdt,
> >       res = fdt_property(fdt, "dma-coherent", NULL, 0);
> >       if (res) return res;
> >   
> > +    if (backend_domid != LIBXL_TOOLSTACK_DOMID) {
> > +        uint32_t domid[1];
> > +
> > +        domid[0] = cpu_to_fdt32(backend_domid);
> > +        res = fdt_property(fdt, "xen,dev-domid", domid, sizeof(domid));
> > +        if (res) return res;
> > +    }
> > +
> >       res = fdt_end_node(fdt);
> >       if (res) return res;
> >   
> > @@ -1218,7 +1227,8 @@ next_resize:
> >               libxl_device_disk *disk = &d_config->disks[i];
> >   
> >               if (disk->protocol == LIBXL_DISK_PROTOCOL_VIRTIO_MMIO)
> > -                FDT( make_virtio_mmio_node(gc, fdt, disk->base, disk->irq) );
> > +                FDT( make_virtio_mmio_node(gc, fdt, disk->base, disk->irq,
> > +                                           disk->backend_domid) );
> >           }
> >   
> >           if (pfdt)
> > --
> > 2.7.4
--
Regards,

Oleksandr Tyshchenko