131 lines
4.4 KiB
Markdown
131 lines
4.4 KiB
Markdown
Haiku PCI Driver Development Under QEMU on Linux
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====================================================
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> WARNING: This is an older guide under kernel 3.x using pci-stub
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> On newer kernels, you have to use vfio.
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Developing Haiku drivers for PCI and PCI Express cards is now a lot easier
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given advancements in IOMMU under Linux. You can effectively detach PCI cards
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from their host operating system and attach them to guest VM's resulting in
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true hardware emulation. In this guide we will be configuring a secondary
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graphics card to be attached to a Haiku virtual machine.
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**Warning**: Any device attached to a VM will be unavailable to the host operating
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system. This means you **cannot** use your primary graphics card, network device,
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etc within a VM and the host operating system at the same time. In this
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example, we have two graphics cards installed in the Linux system.
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IOMMU Setup
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-----------------------
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You will need to have IOMMU hardware support on your motherboard for this
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to function. Most modern AMD A3 socket chips and Intel i3/i5/i7 devices
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have IOMMU built in. If your board does indeed have IOMMU, you will likely
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need to enable IOMMU within the bios of your motherboard before proceeding.
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Linux Setup
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-----------------------
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Now that you have an IOMMU enabled system, you will need to tell Linux to
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fully utilize IOMMU. To do this, you will need to add a few kernel boot
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parameters. Depending on how your system is configured, there may be a few
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places to do this. Here are some example config files:
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* `/etc/default/grub` (`GRUB_CMDLINE_LINUX_DEFAULT`)
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* `/boot/grub/grub.cfg`
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* `/boot/grub/menu.lst`
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* `/boot/refind_linux.conf`
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Enabling OS support IOMMU for IOMMU involves adding one of the following
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kernel boot parameters:
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**AMD:**
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```
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iommu=pt iommu=1
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```
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**Intel:**
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```
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intel_iommu=on
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```
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Now, all we need to do is to reserve the PCI device. We want to make sure
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no host drivers attempt to attach to the PCI device in question.
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First we need to find the PCIID for the device in question. We can find
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this through lcpci. Running lspci shows a bunch of devices. I've identified
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this device as my target:
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```
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07:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cedar [Radeon HD 5000]
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```
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Now, to get the PCI ID, I run lspci again with the -n flag (lspci -n). We find
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the matching BUS ID and we get our PCI ID:
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```
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07:00.0 0300: 1002:68f9
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```
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Now that we have our target PCI ID (`1002:68f9`), we can bind this device to
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a special pci-stub driver.
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We will create two files for this graphics card:
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**`/lib/modprobe.d/pci-stub.conf`:**
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```
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options pci-stub ids=1002:68f9
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```
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**`/lib/modprobe.d/drm.conf`:**
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```
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softdep drm pre: pci-stub
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```
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The first line tells the pci-stub driver to bind to the device in question.
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The second line tells DRM (graphics driver stack) that it should make sure
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pci-stub loads before DRM (ensuring the device is stubbed and not loaded by
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DRM).
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Now we reboot and cross our fingers.
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On my AMD Linux system, we can see that IOMMU is active and functional:
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```
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kallisti5@eris ~ $ dmesg | grep AMD-Vi
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[ 0.119400] [Firmware Bug]: AMD-Vi: IOAPIC[9] not in IVRS table
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[ 0.119406] [Firmware Bug]: AMD-Vi: IOAPIC[10] not in IVRS table
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[ 0.119409] [Firmware Bug]: AMD-Vi: No southbridge IOAPIC found
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[ 0.119412] AMD-Vi: Disabling interrupt remapping
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[ 1.823122] AMD-Vi: Found IOMMU at 0000:00:00.2 cap 0x40
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[ 1.823253] AMD-Vi: Initialized for Passthrough Mode
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```
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And checking for pci-stub we can see it successfully took over my graphics card:
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```
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kallisti5@eris ~ $ dmesg | grep pci-stub
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[ 3.685970] pci-stub: add 1002:68F9 sub=FFFFFFFF:FFFFFFFF cls=00000000/00000000
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[ 3.686002] pci-stub 0000:07:00.0: claimed by stub
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```
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On every boot, the device will be available for attachment to VM's
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Now, we simply attach the device to a VM:
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```
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sudo qemu-system-x86_64 --enable-kvm -hda haiku-nightly-anyboot.image -m 2048 -device pci-assign,host=07:00.0
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```
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If you experience any problems, try looking at kvm messages:
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```
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kallisti5@eris ~ $ dmesg | grep kvm
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```
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If you're doing this for a graphics card generally the qemu window will
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lock up at the bootsplash and the video will appear on the second window.
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Click the qemu window to control the Haiku machine.
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If things go well you will see:
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```
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[ 1966.132176] kvm: Nested Virtualization enabled
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[ 1966.132185] kvm: Nested Paging enabled
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[ 1972.212231] pci-stub 0000:07:00.0: kvm assign device
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[ 1974.186382] kvm: zapping shadow pages for mmio generation wraparound
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```
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