9020sff/mt: say how to use gfxcard+iommu

A special kernel option is required:

intel_iommu=enable,igfx_off

Signed-off-by: Leah Rowe <info@minifree.org>

site/docs/install/dell9020.md

@@ -30,9 +30,9 @@ OR YOU MIGHT BRICK YOUR MACHINE: [SAFETY PRECAUTIONS](../../news/safety.md)**
 | **CPU**                    | Intel Haswell                               |
 | **Graphics**               | Intel HD Graphics |
 | **Memory**                 | DDR3 DIMMs (max 32GB, 4x8GB)    |
-| **Architecture**           | x86_64                                         |
+| **Architecture**           | x86\_64                                         |
 | **Original boot firmware** | Dell UEFI firmware                             |
-| **Intel ME/AMD PSP**       | Present. Can be disabled with me_cleaner.      |
+| **Intel ME/AMD PSP**       | Present. Can be disabled with me\_cleaner.      |
 | **Flash chip**             | 2x SOIC-8, 12MiB (8+4) (96Mbit)           |
 
 
@@ -104,23 +104,47 @@ Graphics cards and IOMMU
 
 IOMMU is buggy for some reason (we don't know why yet), when you plug in
 a graphics card. The graphics card simply won't work. On some of them,
-you can use the console but as soon as you start xorg, it will just b0rk.
+you can use the console but as soon as you start xorg/wayland, it will just b0rk.
 
 Current Libreboot revisions *disable IOMMU by default*, on this board. The
 coreboot code for initialising IOMMU was modified by the Libreboot project, to
 make it a toggle. IOMMU works fine if you use only Intel graphics.
 
+If you want to use IOMMU *with a graphics card*, you also can. Use this Linux
+kernel option at boot:
+
+	intel_iommu=enable,igfx_off
+
+With the above option, IOMMU is enabled *except* for the Intel GPU. However,
+Libreboot also *disables the Intel GPU* in coreboot, entirely, when a graphics
+card is used. With the above option, it's possible that something like Qubes
+may work, which requires an IOMMU to be turned on.
+
+If you are using Intel graphics, and not a graphics card, you can ignore the
+above, and instead fully turn on the IOMMU, without any special kernel options.
+
 The way coreboot works is this: if vt-d is present on the CPU, it enables an
 IOMMU, and only if vt-d is present. This is still the behaviour in Libreboot,
 but Libreboot adds an additional check: if `iommu` is not set in nvram, it
 defaults to on, but if it's set to disabled, then IOMMU is not initialised.
 
+Enable IOMMU
+------------
+
+IOMMU is *disabled by default*, universally, on this board. You can turn it on,
+by modifying the ROM image prior to flashing, or modifying it prior to
+re-flashing.
+
 On all other Haswell boards, LIbreboot enables IOMMU by default. To enable
 it on the 9020, do this on your ROM:
 
 	nvramtool -C libreboot.rom -w iommu=Enable
 
-Then flash the ROM image. You can find nvram
+If you're using a graphics card, please make sure to read the above notes
+about how to use IOMMU; specifically, the part that talks about Linux kernel
+option `intel_iommu=enable,igfx_off`
+
+Then flash the ROM image. You can find nvramtool
 under `src/coreboot/default/util/nvramtool`. Do this in lbmk if you don't
 already havse `src/coreboot/default/`:
 
@@ -137,7 +161,8 @@ in [Libreboot flashing instructions](../install/)
 and [Libreboot external flashing instructions](../install/spi.md).
 
 NOTE: If IOMMU is enabled, you can still use a graphics card, but you must
-pass this on the Linux cmdline paramaters: `iommu=off`
+pass this on the Linux cmdline paramaters: `iommu=off` - or if you need
+IOMMU (e.g. for Qubes), use `intel_iommu=enable,igfx_off` instead.
 
 NOTE2: Libreboot uses a *static option table* on all boards that have nvram,
 which is why you must use the `-C` option on your ROM, to change the static
@@ -201,12 +226,12 @@ If you're already running Libreboot, and you don't have flash protection
 turned on, [internal flashing](../install/) is possible.
 
 Internal flashing can also be done with the original Dell BIOS, if the
-SERVICE_MODE jumper near the PCIe slots is installed. Before flashing,
+SERVICE\_MODE jumper near the PCIe slots is installed. Before flashing,
 
 	rmmod spi-intel-platform
 
 needs to be run to prevent errors. Once Libreboot is installed, the
-SERVICE_MODE jumper can be removed.
+SERVICE\_MODE jumper can be removed.
 
 **Note: The Dell BIOS can write EFI variables to flash when shutting
 down, which could corrupt the newly flashed Libreboot ROM and render