[PATCH 6.6 023/283] xen/virtio: Don't use grant-dma-ops when running as Dom0

[Sasha Levin <sashal@kernel.org>]

From: Teddy Astie <teddy.astie@vates.tech>

[ Upstream commit dc8ea8714311e549ee93a2b0bdd5487d20bfadbf ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/xen/grant-dma-ops.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index 76f6f26265a3b..12fbe89382593 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -362,7 +362,8 @@ 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;
-- 
2.51.0