doc: make UIO safety warning more visible in Linux guide

The GSG has a note warning that use of UIO is inherently unsafe due to
lack of IOMMU protection. However, this was only flagged as a "NOTE",
meaning it could easily be missed. Changing the rst tag from "note" to
"warning" and moving it to the top of the UIO subsection makes this a
lot more visible to users.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

diff --git a/doc/guides/linux_gsg/linux_drivers.rst b/doc/guides/linux_gsg/linux_drivers.rst
index bd983b4d81787493f3ea778c256fa3ea4bb77074..f0a274df6a892d29d7482a3abdc3841dda79c5e0 100644 (file)
--- a/doc/guides/linux_gsg/linux_drivers.rst
+++ b/doc/guides/linux_gsg/linux_drivers.rst
@@ -153,6 +153,11 @@ After that, VFIO can be used with hardware devices as usual.
 UIO
 ---
 
+.. warning::
+
+   Using UIO drivers is inherently unsafe due to this method lacking IOMMU protection,
+   and can only be done by root user.
+
 In situations where using VFIO is not an option, there are alternative drivers one can use.
 In many cases, the standard ``uio_pci_generic`` module included in the Linux kernel
 can be used as a substitute for VFIO. This module can be loaded using the command:
@@ -195,11 +200,6 @@ It can be loaded as shown below:
    in GRUB command line on x86_64 systems,
    or add ``iommu.passthrough=1`` on aarch64 systems.
 
-.. note::
-
-   Using UIO drivers is inherently unsafe due to this method lacking IOMMU protection,
-   and can only be done by root user.
-
 .. _bifurcated_driver:
 
 Bifurcated Driver