Files
chiasson-nix/modules/system/gpu-passthru.nix
T

384 lines
13 KiB
Nix

{ ... }: {
flake.nixosModules.systemGpuPassthru =
{ config, lib, pkgs, ... }:
let
cfg = config.chiasson.system.gpuPassthru;
vfioIds = lib.concatStringsSep "," cfg.pciIds;
# Must match the Windows host installer build (B7-244-4bb2c58f).
lgRev = "4bb2c58fb6d0df9e863ad45924dd4decc7e9cf4e";
lgVersion = "B7-244-4bb2c58f";
# Tarball hashes omit submodules; fetchSubmodules needs the git tree hash.
lgHash = "sha256-Dc0sFnJVM0xJ0FfIQqGQKxFUj6mhp3qgB772h3Dgowc=";
# https://wiki.nixos.org/wiki/Looking_Glass — systemd 258+ needs namespaces=[]
# and an explicit ACL; seccomp can block mmap on /dev/kvmfr0.
lgQemuVerbatimConfig = ''
namespaces = []
seccomp_sandbox = 0
security_driver = "none"
security_default_confined = 0
security_require_confined = 0
cgroup_device_acl = [
"/dev/null", "/dev/full", "/dev/zero",
"/dev/random", "/dev/urandom",
"/dev/ptmx", "/dev/kvm", "/dev/kqemu",
"/dev/rtc", "/dev/hpet",
"/dev/vfio/", "/dev/vfio/vfio",
"/dev/kvmfr0", "c 234:* rwm",
"/dev/disk/", "/dev/disk/by-id/",
"/dev/bus/usb/",
]
'';
in
{
options.chiasson.system.gpuPassthru = {
enable = lib.mkEnableOption ''
Bind passthrough GPU(s) to VFIO, run the host on Intel iGPU, and enable libvirt +
Looking Glass for a Windows gaming VM.
Prerequisites (manual, one-time):
- BIOS: VT-d/IOMMU on, Above 4G Decoding / Resizable BAR on
- Move host monitors to motherboard (Intel) ports; dummy HDMI/DP plug on passthrough GPU
- Wipe the VM disk before first boot: `wipefs -a <windowsDisk>`
- Verify IOMMU groups after switch: GPU functions should be isolated
Rollout: leave `enable = false` until cabling and disk backup are done, then rebuild and switch.
'';
pciIds = lib.mkOption {
type = lib.types.listOf lib.types.str;
default = [ ];
example = [ "10de:1f07" "10de:10f9" "10de:1ada" "10de:1adb" ];
description = ''
PCI vendor:device IDs to bind to vfio-pci (all GPU functions: VGA, audio, USB, etc.).
'';
};
windowsDisk = lib.mkOption {
type = lib.types.str;
default = "";
example = "/dev/disk/by-id/ata-CT1000MX500SSD1_1830E14B054A";
description = ''
Whole-disk by-id path for the Windows VM (raw block passthrough). Must not be mounted by the host.
'';
};
lookingGlass = {
enable = lib.mkOption {
type = lib.types.bool;
default = true;
description = ''
Load the kvmfr kernel module and grant QEMU access to /dev/kvmfr0 for Looking Glass
(required for NVIDIA VFIO; plain /dev/shm IVSHMEM causes DMA mapping failures).
'';
};
shmSizeMiB = lib.mkOption {
type = lib.types.int;
default = 32;
description = ''
kvmfr shared memory size (MiB). Must match `kvmfr.static_size_mb` and the VM
`memory-backend-file` size in the domain XML.
'';
};
captureOnFocus = lib.mkOption {
type = lib.types.bool;
default = true;
description = ''
Grab keyboard/mouse when the Looking Glass window is focused. Set `false` to
keep input on the Linux host while viewing the guest.
'';
};
};
vm = {
enable = lib.mkOption {
type = lib.types.bool;
default = false;
description = ''
Declaratively define the Windows VM via NixVirt (host module must import NixVirt and set
`virtualisation.libvirt.connections`).
'';
};
name = lib.mkOption {
type = lib.types.str;
default = "win11";
description = "libvirt domain name.";
};
memoryGiB = lib.mkOption {
type = lib.types.int;
default = 16;
description = "VM RAM in GiB (informational; domain XML is authoritative).";
};
vcpus = lib.mkOption {
type = lib.types.int;
default = 8;
description = "vCPU count (informational; domain XML is authoritative).";
};
installMode = lib.mkOption {
type = lib.types.bool;
default = true;
description = ''
Use install domain (ISO, no GPU). Set `false` after Windows is installed.
'';
};
};
hugepages.enable = lib.mkOption {
type = lib.types.bool;
default = false;
description = "Reserve 2 MiB hugepages for Looking Glass IVSHMEM (enable if frame drops).";
};
libvirtUsers = lib.mkOption {
type = lib.types.listOf lib.types.str;
default = [ ];
description = "Users added to libvirtd, kvm, and disk groups.";
};
};
config = lib.mkIf cfg.enable (lib.mkMerge [
{
assertions = [
{
assertion = cfg.pciIds != [ ];
message = "chiasson.system.gpuPassthru: pciIds must list every passthrough GPU function.";
}
{
assertion = cfg.windowsDisk != "";
message = "chiasson.system.gpuPassthru: windowsDisk must be set to a /dev/disk/by-id/ path.";
}
{
assertion = cfg.libvirtUsers != [ ];
message = "chiasson.system.gpuPassthru: libvirtUsers must name at least one user.";
}
];
boot.kernelParams = [
"intel_iommu=on"
"iommu=pt"
"kvm.ignore_msrs=1"
"vfio-pci.ids=${vfioIds}"
];
boot.initrd.kernelModules = [
"vfio_pci"
"vfio"
"vfio_iommu_type1"
];
boot.blacklistedKernelModules = [
"nouveau"
"nvidia"
"nvidia_drm"
"nvidia_modeset"
"i2c_nvidia_gpu"
"mt7921e"
"mt7925e"
];
boot.extraModprobeConfig = ''
softdep nvidia pre: vfio-pci
softdep nvidia_drm pre: vfio-pci
softdep nouveau pre: vfio-pci
options vfio_iommu_type1 allow_unsafe_interrupts=1
'';
services.xserver.videoDrivers = lib.mkForce [ "modesetting" ];
hardware.nvidia-container-toolkit.enable = lib.mkForce false;
chiasson.system.gaming.sunshine.cudaSupport = lib.mkForce false;
# libvirt enables ZFS storage pools on Linux by default, which pulls in
# zfs-user (currently broken to build on nixos-unstable). Raw block disk
# passthrough does not need libvirt ZFS support.
nixpkgs.overlays =
[
(final: prev: {
libvirt = prev.libvirt.override { enableZfs = false; };
})
]
++ lib.optionals cfg.lookingGlass.enable [
(final: prev: {
looking-glass-client = prev.looking-glass-client.overrideAttrs (old: {
version = lgVersion;
src = prev.fetchFromGitHub {
owner = "gnif";
repo = "LookingGlass";
rev = lgRev;
hash = lgHash;
fetchSubmodules = true;
};
patches = old.patches;
postUnpack = ''
echo ${lgRev} > $sourceRoot/VERSION
export sourceRoot="$sourceRoot/client"
'';
});
})
];
programs.virt-manager.enable = true;
virtualisation.spiceUSBRedirection.enable = true;
virtualisation.libvirtd = {
enable = true;
onBoot = "ignore";
onShutdown = "shutdown";
qemu = {
package = pkgs.qemu_kvm;
# GPU + raw block passthrough needs root (or fragile per-device ACLs).
runAsRoot = true;
swtpm.enable = true;
verbatimConfig = lib.mkIf cfg.lookingGlass.enable (lib.mkForce lgQemuVerbatimConfig);
};
};
systemd.services.libvirtd.restartTriggers = [
"${pkgs.qemu_kvm}/bin/qemu-system-x86_64"
];
environment.systemPackages =
with pkgs;
[
virt-manager
qemu_kvm
OVMF
edk2
looking-glass-client
swtpm
]
++ lib.optionals cfg.lookingGlass.enable [
(writeShellScriptBin "looking-glass-toggle" ''
set -euo pipefail
pkill -f 'looking-glass-client' || true
exec looking-glass-client -F -m 97
'')
];
# B7 defaults to /dev/kvmfr0; pin SPICE to the fixed port in the domain XMLs.
environment.etc."looking-glass-client.ini" = lib.mkIf cfg.lookingGlass.enable (lib.mkForce {
text = ''
[app]
shmFile=/dev/kvmfr0
allowDMA=yes
[win]
fullScreen=yes
[spice]
enable=yes
host=127.0.0.1
port=5900
input=yes
audio=yes
clipboard=yes
[input]
captureOnFocus=${lib.boolToString cfg.lookingGlass.captureOnFocus}
escapeKey=97
'';
});
users.groups.libvirtd.members = cfg.libvirtUsers;
users.users =
lib.genAttrs cfg.libvirtUsers (_: {
extraGroups = [
"libvirtd"
"kvm"
"disk"
];
})
// {
qemu-libvirtd.extraGroups = [
"kvm"
"disk"
];
};
}
{
systemd.tmpfiles.rules = [
"d /var/lib/libvirt/boot 0755 root root -"
];
}
(lib.mkIf cfg.lookingGlass.enable {
boot.extraModulePackages = lib.mkAfter [ config.boot.kernelPackages.kvmfr ];
boot.initrd.kernelModules = lib.mkAfter [ "kvmfr" ];
boot.kernelModules = lib.mkAfter [ "kvmfr" ];
boot.kernelParams = lib.mkAfter [
"kvmfr.static_size_mb=${toString cfg.lookingGlass.shmSizeMiB}"
];
boot.extraModprobeConfig = lib.mkAfter ''
options kvmfr static_size_mb=${toString cfg.lookingGlass.shmSizeMiB}
'';
services.udev.packages = [
(pkgs.writeTextFile {
name = "kvmfr-udev";
text = ''
SUBSYSTEM=="kvmfr", GROUP="kvm", MODE="0660", TAG+="uaccess"
'';
destination = "/etc/udev/rules.d/70-kvmfr.rules";
})
];
# insmod from the nix store: extraModulePackages only lands in
# /run/booted-system/kernel-modules after a reboot.
systemd.services.kvmfr = {
description = "Looking Glass kvmfr module";
wantedBy = [ "multi-user.target" ];
before = [
"libvirtd.service"
"libvirtd-config.service"
"libvirt-guests.service"
];
after = [ "systemd-modules-load.service" ];
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
ExecStart = pkgs.writeShellScript "kvmfr-start" (
let
kvmfrKo = "${config.boot.kernelPackages.kvmfr}/lib/modules/${config.boot.kernelPackages.kernel.modDirVersion}/kernel/drivers/misc/kvmfr.ko";
shmMiB = toString cfg.lookingGlass.shmSizeMiB;
in
''
set -euo pipefail
if [ -e /dev/kvmfr0 ] && [ ! -c /dev/kvmfr0 ]; then
rm -f /dev/kvmfr0
fi
if [ -c /dev/kvmfr0 ]; then
exit 0
fi
if ${pkgs.kmod}/bin/lsmod | ${pkgs.gnugrep}/bin/grep -q '^kvmfr '; then
${pkgs.kmod}/bin/rmmod kvmfr
fi
if [ ! -f ${kvmfrKo} ]; then
echo "kvmfr: module missing at ${kvmfrKo}" >&2
exit 1
fi
${pkgs.kmod}/bin/insmod ${kvmfrKo} static_size_mb=${shmMiB}
if [ ! -c /dev/kvmfr0 ]; then
echo "kvmfr: /dev/kvmfr0 not created (static_size_mb=${shmMiB})" >&2
exit 1
fi
''
);
};
};
systemd.services.libvirtd = lib.mkIf cfg.lookingGlass.enable {
after = [ "kvmfr.service" ];
requires = [ "kvmfr.service" ];
};
})
(lib.mkIf cfg.hugepages.enable {
boot.kernelParams = [ "hugepagesz=2M" "hugepages=64" ];
})
]);
};
}