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| author | Ahmad Fatoum <ahmad@a3f.at> | 2021-02-28 20:08:35 +0100 |
|---|---|---|
| committer | Sascha Hauer <s.hauer@pengutronix.de> | 2021-03-04 12:11:24 +0100 |
| commit | 17a6750abe2355fd7a418fd392983ea0895d2d9a (patch) | |
| tree | 9052171756ae379bed99001bb58b46bf7b9c25f6 /Documentation/user | |
| parent | 12d208815b660ce5ac83503acef5a7aed81afc10 (diff) | |
| download | barebox-17a6750abe2355fd7a418fd392983ea0895d2d9a.tar.gz barebox-17a6750abe2355fd7a418fd392983ea0895d2d9a.tar.xz | |
virtio: support virtio-based device drivers over PCI
This driver provides support for virtio based paravirtual device
drivers over PCI. This is useful with Qemu for boards that barebox
has PCI support for, e.g. MIPS Malta.
Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Diffstat (limited to 'Documentation/user')
| -rw-r--r-- | Documentation/user/virtio.rst | 30 |
1 files changed, 17 insertions, 13 deletions
diff --git a/Documentation/user/virtio.rst b/Documentation/user/virtio.rst index 5d2a8c8208..7e125c0ca8 100644 --- a/Documentation/user/virtio.rst +++ b/Documentation/user/virtio.rst @@ -20,7 +20,7 @@ just the guest's device driver "knows" it is running in a virtual environment, and cooperates with the hypervisor. This enables guests to get high performance network and disk operations, and gives most of the performance benefits of paravirtualization. In the barebox case, the guest is barebox itself, while the -virtual environment will normally be QEMU_ targets like ARM, RISC-V and x86. +virtual environment will normally be QEMU_ targets like ARM, MIPS, RISC-V or x86. Status ------ @@ -31,8 +31,8 @@ embedded devices models like ARM/RISC-V, which does not normally come with PCI support might use simple memory mapped device (MMIO) instead of the PCI device. The memory mapped virtio device behaviour is based on the PCI device specification. Therefore most operations including device initialization, -queues configuration and buffer transfers are nearly identical. Only MMIO -is currently supported in barebox. +queues configuration and buffer transfers are nearly identical. Both MMIO +and non-legacy PCI are supported in barebox. The VirtIO spec defines a lots of VirtIO device types, however at present only block, console and RNG devices are supported. @@ -67,16 +67,20 @@ to pass barebox a fixed-up device tree describing the ``virtio-mmio`` rings. Except for the console, multiple instances of a VirtIO device can be created -by appending more '-device' parameters. For example to create one HWRNG -and 2 block devices:: - - $ qemu-system-arm -m 256M -M virt -nographic \ - -kernel ./images/barebox-dt-2nd.img \ - -device virtio-rng-device \ - -drive if=none,file=/tmp/first.hdimg,format=raw,id=hd0 \ - -device virtio-blk-device,drive=hd0 \ - -drive if=none,file=/tmp/second.hdimg,format=raw,id=hd1 \ - -device virtio-blk-device,drive=hd1 +by appending more '-device' parameters. For example to extend a MIPS +malta VM with one HWRNG and 2 block VirtIO PCI devices:: + + $ qemu-system-mips -m 256M -M malta -serial stdio \ + -bios ./images/barebox-qemu-malta.img -monitor null \ + -device virtio-rng-pci,disable-legacy=on \ + -drive if=none,file=image1.hdimg,format=raw,id=hd0 \ + -device virtio-blk-pci,drive=hd0,disable-legacy=on \ + -drive if=none,file=image2.hdimg,format=raw,id=hd1 \ + -device virtio-blk-pci,drive=hd1,disable-legacy=on + +Note the use of ``disable-legacy=on``. barebox doesn't support legacy +or transitional VirtIO devices. Some versions of QEMU may need to +have ``,disable-modern=off`` specfied as well. .. _VirtIO: http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.pdf .. _qemu: https://www.qemu.org |