Re: [libvirt] [PATCH] qemu: map "virtio" video model to "virt" machtype correctly (arm/aarch64)

On 09/16/16 08:28, Martin Kletzander wrote: > On Fri, Sep 16, 2016 at 06:04:46AM +0200, Laszlo Ersek wrote: >> Most of QEMU's PCI display device models, such as: >> >> libvirt video/model/@type QEMU -device >> ------------------------- ------------ >> cirrus cirrus-vga >> vga VGA >> qxl qxl-vga >> virtio virtio-vga >> >> come with a linear framebuffer (sometimes called "VGA compatibility >> framebuffer"). This linear framebuffer lives in one of the PCI device's >> MMIO BARs, and allows guest code (primarily: firmware drivers, and >> non-accelerated OS drivers) to display graphics with direct memory >> access. >> >> Due to architectural reasons on aarch64/KVM hosts, this kind of >> framebuffer doesn't / can't work in >> >> qemu-system-(arm|aarch64) -M virt >> >> machines. Cache coherency issues guarantee a corrupted / unusable >> display. >> The problem has been researched by several people, including kvm-arm >> maintainers, and it's been decided that the best way (practically the >> only >> way) to have boot time graphics for such guests is to consolidate on >> QEMU's "virtio-gpu-pci" device. >> >>> From <https://bugzilla.redhat.com/show_bug.cgi?id=1195176>;, libvirt >> supports >> >> <devices> >> <video> >> <model type='virtio'/> >> </video> >> </devices> >> >> but libvirt unconditionally maps @type='virtio' to QEMU's "virtio-vga" >> device model. (See the qemuBuildDeviceVideoStr() function and the >> "qemuDeviceVideo" enum impl.) >> >> According to the above, this is not right for the "virt" machine type; >> the >> qemu-system-(arm|aarch64) binaries don't even recognize the "virtio-vga" >> device model (justifiedly). Whereas "virtio-gpu-pci", which is a pure >> virtio device without a compatibility framebuffer, is available, and >> works >> fine. >> >> (The ArmVirtQemu ("AAVMF") platform of edk2 -- that is, the UEFI firmware >> for "virt" -- supports "virtio-gpu-pci", as of upstream commit >> 3ef3209d3028. See >> <https://tianocore.acgmultimedia.com/show_bug.cgi?id=66>.) >> >> Override the default mapping of "virtio", from "virtio-vga" to >> "virtio-gpu-pci", if qemuDomainMachineIsVirt() evaluates to true. >> >> Cc: Andrea Bolognani <abologna(a)redhat.com&gt; >> Cc: Drew Jones <drjones(a)redhat.com&gt; >> Cc: Marc-André Lureau <marcandre.lureau(a)redhat.com&gt; >> Suggested-by: Marc-André Lureau <marcandre.lureau(a)redhat.com&gt; >> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1372901 >> Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; > > Very nicely written, makes sense and since virtio-vga didn't work for > virt machines, there is no problem with changing it. Thank you! > One small nit though, syntax-check will complain that one of the lines > in the .args file is longer, you can either use 'tests/test-wrap-argv.pl > --in-place > tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args' > or just squash this diff in, whatever you find easier: While working on the test data, I consulted other files, and I noticed that they were carefully wrapped. I tried to do the same -- did I fail? $ wc -L \ tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args 74 tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args and "tests/test-wrap-argv.pl" has my $max_len = 78; Hmmm... After running the script, it looks like I was too cautious. The problem is actually that I broke one of those lines too early, and now it's too short. :)

I'll send a v2. Thanks! Laszlo > diff --git > i/tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args > w/tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args > index 56dbdfb66fa2..76ee977a3ca2 100644 > --- i/tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args > +++ w/tests/qemuxml2argvdata/qemuxml2argv-aarch64-video-virtio-gpu-pci.args > @@ -20,7 +20,7 @@ QEMU_AUDIO_DRV=none \ > addr=0x1 \ > -device ioh3420,port=0x9,chassis=2,id=pci.2,bus=pcie.0,multifunction=on,\ > addr=0x1.0x1 \ > --device virtio-net-pci,vlan=0,id=net0,mac=52:54:00:73:34:53,bus=pci.1,\ > -addr=0x0,bootindex=1 \ > +-device > virtio-net-pci,vlan=0,id=net0,mac=52:54:00:73:34:53,bus=pci.1,addr=0x0,\ > +bootindex=1 \ > -net user,vlan=0,name=hostnet0 \ > -device virtio-gpu-pci,id=video0,bus=pci.2,addr=0x0 > -- > > Other than that, with that small thing fixed: > > Acked-by: Martin Kletzander <mkletzan(a)redhat.com&gt; -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list