xen/virtio: Don't use grant-dma-ops when running as Dom0

Dom0 inherit devices from the machine and is usually in PV mode.
If we are running in a virtual that has virtio devices, these devices
would be considered as using grants with Dom0 as backend, while being
the said Dom0 itself, while we want to use these devices like regular
PCI devices.

Fix this by preventing grant-dma-ops from being used when running as Dom0
(initial domain). We still keep the device-tree logic as-is.

Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
Fixes: 61367688f1fb0 ("xen/virtio: enable grant based virtio on x86")
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <6698564dd2270a9f7377b78ebfb20cb425cabbe8.1767720955.git.teddy.astie@vates.tech>

diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index 14077d23f2a19edceaeed55c02b3c655fdc01863..c2603e700178637403d4cef040abc12f63a9c541 100644 (file)
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -366,7 +366,8 @@ static int xen_grant_init_backend_domid(struct device *dev,
        if (np) {
                ret = xen_dt_grant_init_backend_domid(dev, np, backend_domid);
                of_node_put(np);
-       } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT) || xen_pv_domain()) {
+       } else if (!xen_initial_domain() &&
+                  (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT) || xen_pv_domain())) {
                dev_info(dev, "Using dom0 as backend\n");
                *backend_domid = 0;
                ret = 0;