Difference between revisions of "R-Car/Virtualization/VFIO"

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(Update for v2 on the host, handling Clock and PM Domains)
(Update for v2 on the guest, passing interrups)
Line 37: Line 37:
 
* Build a guest kernel using:
 
* Build a guest kernel using:
 
** Repository:  https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git
 
** Repository:  https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git
** Branch: "topic/rcar3-virt-gpio-passthrough"
+
** Branch: "topic/rcar3-virt-gpio-passthrough-v2"
 
** Config: "virt_defconfig"
 
** Config: "virt_defconfig"
  
 
* Build QEMU using:
 
* Build QEMU using:
 
** Repository: https://github.com/geertu/qemu.git
 
** Repository: https://github.com/geertu/qemu.git
** Branch: "topic/rcar3-virt-gpio-passthrough"
+
** Branch: "topic/rcar3-virt-gpio-passthrough-v2"
  
 
* When starting QEMU, specify pass-through of the GPIO6 platform device.  The device specifier consists of three parts:
 
* When starting QEMU, specify pass-through of the GPIO6 platform device.  The device specifier consists of three parts:
Line 71: Line 71:
 
<pre>
 
<pre>
 
Booting Linux on physical CPU 0x0000000000 [0x411fd073]
 
Booting Linux on physical CPU 0x0000000000 [0x411fd073]
Linux version 4.15.0-arm64-virt-00009-g1e04d78a91abdbbd ...
+
Linux version 4.16.0-arm64-virt-00010-g8f416425ed2e81bb ...
 
...
 
...
gpio_rcar c000000.e6055400.gpio: missing clock, ignoring
 
gpio_rcar c000000.e6055400.gpio: missing IRQ, ignoring
 
 
gpio_rcar c000000.e6055400.gpio: driving 32 GPIOs
 
gpio_rcar c000000.e6055400.gpio: driving 32 GPIOs
 
...
 
...
Line 89: Line 87:
 
--- /sys/firmware/devicetree/base.orig
 
--- /sys/firmware/devicetree/base.orig
 
+++ /sys/firmware/devicetree/base
 
+++ /sys/firmware/devicetree/base
@@ -124,6 +124,13 @@
+
@@ -124,6 +124,14 @@
 
                 compatible = "qemu,platform", "simple-bus";
 
                 compatible = "qemu,platform", "simple-bus";
 
                 interrupt-parent = <0x8001>;
 
                 interrupt-parent = <0x8001>;
Line 98: Line 96:
 
+                      compatible = "renesas,rcar-gen3-gpio";
 
+                      compatible = "renesas,rcar-gen3-gpio";
 
+                      gpio-controller;
 
+                      gpio-controller;
 +
+                      interrupts = <0x0 0x70 0x4>;
 
+                      reg = <0x0 0x50>;
 
+                      reg = <0x0 0x50>;
 
+              };
 
+              };

Revision as of 13:18, 25 April 2018

Device Pass-Through Using VFIO

Platform Device Pass-Through Prototype

This is a proof-of-concept showing how to provide guest access to an R-Car GPIO controller block on the Renesas Salvator-X and Salvator-XS boards.

Host Side

  • Configure workarounds for missing functionality:
$ echo 1 > /sys/module/vfio/parameters/enable_unsafe_noiommu_mode
  • Unbind GPIO6 from the "gpio-rcar" driver:
$ echo e6055400.gpio > /sys/bus/platform/drivers/gpio_rcar/unbind
gpio gpiochip6: REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED
  • Bind GPIO6 to the "vfio-platform" driver, for pass-through to guests:
$ echo vfio-platform > /sys/bus/platform/devices/e6055400.gpio/driver_override
$ echo e6055400.gpio > /sys/bus/platform/drivers/vfio-platform/bind
iommu: Adding device e6055400.gpio to group 0
vfio-platform e6055400.gpio: Adding kernel taint for vfio-noiommu group on device

Guest Side

  • When starting QEMU, specify pass-through of the GPIO6 platform device. The device specifier consists of three parts:
    $1a
    the device's node name, or
    $1b
    the full path to the device's node in sysfs,
    $2
    the manufacturer part of the device's compatible value,
    $3
    the model part of the device's compatible value.

I.e.:

-device vfio-platform,host=$1a,manufacturer=$2,model=$3
-device vfio-platform,host=e6055400.gpio,manufacturer=renesas,model=rcar-gen3-gpio
-device vfio-platform,sysfsdev=$1b,manufacturer=$2,model=$3
-device vfio-platform,sysfsdev=/sys/bus/platform/devices/e6055400.gpio,manufacturer=renesas,model=rcar-gen3-gpio

Full command line:

$ qemu-system-aarch64 -enable-kvm -M virt -cpu cortex-a57 -m 1024 -nographic \
        -kernel /path/to/guest/kernel/Image \
        -device vfio-platform,host=e6055400.gpio,manufacturer=renesas,model=rcar-gen3-gpio

Guest kernel output:

Booting Linux on physical CPU 0x0000000000 [0x411fd073]
Linux version 4.16.0-arm64-virt-00010-g8f416425ed2e81bb ...
...
gpio_rcar c000000.e6055400.gpio: driving 32 GPIOs
...

Host kernel output:

vfio-platform e6055400.gpio: reset
vfio-platform e6055400.gpio: vfio-noiommu device opened by user (qemu-system-aar:3003)
  • Analysis of "/sys/firmware/devicetree/base" using "dtx_diff" shows that "e6055400.gpio@0" has been added as a subnode to the existing "platform@c000000" node:
--- /sys/firmware/devicetree/base.orig
+++ /sys/firmware/devicetree/base
@@ -124,6 +124,14 @@
                compatible = "qemu,platform", "simple-bus";
                interrupt-parent = <0x8001>;
                ranges = <0x0 0x0 0xc000000 0x2000000>;
+
+               e6055400.gpio@0 {
+                       #gpio-cells = <0x2>;
+                       compatible = "renesas,rcar-gen3-gpio";
+                       gpio-controller;
+                       interrupts = <0x0 0x70 0x4>;
+                       reg = <0x0 0x50>;
+               };
        };

        pmu {
  • Export GPIOs used for LEDs, and turn all LEDs off:
# base=$(cat /sys/class/gpio/gpiochip*/base)
# for i in 11 12 13; do
    echo $(($base + $i)) > /sys/class/gpio/export
    echo low > /sys/class/gpio/gpio$(($base + $i))/direction
done
  • Cycle through all LEDs, letting them blink once:
# for i in 11 12 13; do
    echo high > /sys/class/gpio/gpio$(($base + $i))/direction
    sleep 1
    echo low > /sys/class/gpio/gpio$(($base + $i))/direction
done
  • Shut the guest down:
# poweroff

Guest kernel output:

reboot: Power down

Host kernel output:

vfio-platform e6055400.gpio: reset

The GPIO module has been reset, turning on all three LEDs.

Future Work

  • IOMMU groups
  • Interrupts