7 Commits

8 changed files with 122 additions and 58 deletions

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@@ -75,12 +75,6 @@ Enable-NetFirewallRule -DisplayGroup "Remote Desktop"
Put your public key in `C:\ProgramData\ssh\administrators_authorized_keys` for an Administrator
account. `vm-native-verify` uses that key.
SSH into the guest fails with `Corrupted MAC on input` until the host has the e1000e offload rule
from the `vfio-native` package. The emulated NIC's TX offloads corrupt integrity-checked traffic on
the host side of the tap; SMB tolerates it, SSH does not. The package installs a udev rule that
turns the offloads off on every libvirt tap as it appears, and `vm-native-setup` says so if it is
missing.
## 3. Make the NVMe driver boot-critical
The disk is about to move from virtio to emulated NVMe, and Windows only loads boot-start drivers
@@ -127,9 +121,14 @@ Two things it asks or warns about:
Before the first boot, if the host has less free memory than the guest's RAM, free and compact
it so the guest lands on transparent hugepages; `vm-native-setup` prints the two commands when it
applies. The NIC stays `e1000e`, so the network survives the driver removal in the next step. Do not use
applies. The NIC stays `igb`, so the network survives the driver removal in the next step. Do not use
virtiofs for host files: it is a virtio device the scanner names, and its shared memory backing
blocks transparent hugepages for the whole guest. Share over SMB on the e1000e link instead.
blocks transparent hugepages for the whole guest. Share over SMB on the `igb` link instead.
The interface asks for MTU 9000, and the package's hook turns GSO and GRO on for the tap. Together
they take the inbound link from 2.9 to 14 Gbit/s; neither does anything alone. The libvirt network
needs `<mtu size='9000'/>` too, and the guest needs *Jumbo Packet* 9014 with its interface MTU at
9000 - setting the adapter property alone leaves the IP MTU at 1500 and gains nothing.
## 5. Remove the virtio drivers and the agents

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@@ -8,7 +8,7 @@
# vfio-native-qemu QEMU 11.1.1 with the platform-identity patches, in /opt
pkgname=vfio-native
pkgver=1.1.1
pkgver=1.3.2
pkgrel=1
pkgdesc="Present a libvirt guest as a self-consistent physical machine, and tune it"
arch=('any')
@@ -48,7 +48,6 @@ package() {
# this coexists with whatever hook the host already has.
install -Dm755 scripts/libvirt-hook-cpu-isolation.sh \
"${pkgdir}/etc/libvirt/hooks/qemu.d/10-cpu-isolation.sh"
# e1000e offloads corrupt integrity-checked traffic on libvirt taps; host-wide by nature
install -Dm644 scripts/99-vfio-native-vnet-offload.rules \
"${pkgdir}/usr/lib/udev/rules.d/99-vfio-native-vnet-offload.rules"
install -Dm755 scripts/libvirt-hook-vnet-offload.sh \
"${pkgdir}/etc/libvirt/hooks/qemu.d/20-vnet-offload.sh"
}

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@@ -49,11 +49,11 @@ post_install() {
'native' is a good default if you would rather not maintain anything.
A udev rule (99-vfio-native-vnet-offload.rules) turns TX offloads off on every
libvirt tap as it appears. The emulated e1000e NIC corrupts integrity-checked
traffic with them on; SSH to the guest fails with "Corrupted MAC on input".
It applies to every VM on the host; the throughput cost on a host<->guest
link is not measurable.
A hook at /etc/libvirt/hooks/qemu.d/20-vnet-offload.sh turns GSO and GRO on
for the guest's tap. With the interface's MTU 9000 that takes the inbound link
from 2.9 to 14 Gbit/s; neither does anything alone. The libvirt network needs
<mtu size='9000'/> too, and the guest needs Jumbo Packet 9014 with its
interface MTU at 9000.
A libvirt hook is installed at /etc/libvirt/hooks/qemu.d/10-cpu-isolation.sh.
It keeps host processes off the cores the guest is pinned to, automatically,

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@@ -1,8 +0,0 @@
# vfio-native: the emulated e1000e NIC's TX checksum and segmentation offloads
# corrupt packets on the host side of a libvirt tap. SMB tolerates it; SSH fails
# with "Corrupted MAC on input" and any integrity-checked protocol breaks.
# Measured on a Zen 4 host with QEMU 11.1.1. Disabling the offloads on every
# libvirt tap as it appears fixes it; on a host<->guest link the throughput
# cost is not measurable. libvirt's <driver><host .../> attributes are ignored
# for e1000e, and a libvirt hook must not call virsh, hence udev.
ACTION=="add", SUBSYSTEM=="net", KERNEL=="vnet*", RUN+="/usr/bin/ethtool -K %k tx off gso off gro off tso off"

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@@ -1,12 +1,18 @@
#!/bin/bash
# Waits for a just-started guest's network to actually come up, then turns
# kvm_amd cpuid_passthrough on.
# Keeps the kvm_amd cpuid_passthrough switch correct across a guest's whole life,
# in-guest reboots included.
#
# The readiness signal is the guest's own tap RX counter: it is fresh every boot,
# it needs nothing enabled inside the guest (no SSH, no RDP, no agent), and it only
# moves once the guest's NIC driver has really loaded - which is well past the CPU
# enumeration that the switch must not change under. A DHCP lease left over from a
# previous boot cannot trip it early.
# The switch must be OFF (N) while the guest enumerates CPUID at boot or Windows
# hangs, and ON (Y) once it is up, where it clears the timer detection. The libvirt
# hook only fires at VM start and stop, so a guest-initiated reboot would otherwise
# re-enumerate with the switch still Y and hang. This watcher drops it to N on every
# QEMU RESET and raises it again once the guest's NIC is back up.
#
# Readiness signal: the guest tap's rx_packets counter growing past a baseline. It
# only moves once the guest NIC driver has loaded, well past CPU enumeration, and it
# needs nothing enabled inside the guest. The counter is cumulative and does NOT
# reset on an in-guest reboot, so readiness is growth past the value captured at the
# reset, not an absolute threshold.
#
# Launched as a transient systemd unit by the cpuid-passthrough hook, so it is free
# to call virsh (the hook itself must not - that deadlocks libvirtd).
@@ -18,24 +24,43 @@ V="virsh -c qemu:///system"
running() { [ "$($V domstate "$DOMAIN" 2>/dev/null)" = running ]; }
tap=""
i=0
for _ in $(seq 1 65); do # ~195 s cap, then flip anyway if still up
tap=$($V domiflist "$DOMAIN" 2>/dev/null | awk '$1 ~ /^(vnet|tap|macvtap)/ {print $1; exit}')
RX="/sys/class/net/$tap/statistics/rx_packets"
rx() { cat "$RX" 2>/dev/null || echo 0; }
set_N() { echo N > "$PARAM/cpuid_passthrough"; }
set_Y() { printf '%s' "$BRAND" > "$PARAM/brand_string"; echo Y > "$PARAM/cpuid_passthrough"; }
# Wait until the tap rx counter grows at least 4 past $1 (guest NIC driver up again).
# The iteration floor keeps a stray pre-OS packet (a UEFI netboot attempt) from
# tripping the flip before the guest is even past its interrupt and timer setup.
wait_net_up() {
local base=$1 i=0
for _ in $(seq 1 100); do # ~300 s cap, then raise anyway if still up
i=$((i + 1))
running || { sleep 3; continue; } # not "running" yet at prepare time - wait
[ -z "$tap" ] && tap=$($V domiflist "$DOMAIN" 2>/dev/null |
awk '$1 ~ /^(vnet|tap|macvtap)/ {print $1; exit}')
rx="/sys/class/net/$tap/statistics/rx_packets"
# the iteration floor keeps a stray pre-OS packet (a UEFI netboot attempt) from
# tripping the flip before the guest is even past its interrupt and timer setup
if [ "$i" -ge 4 ] && [ -n "$tap" ] && [ -r "$rx" ] &&
[ "$(cat "$rx" 2>/dev/null || echo 0)" -ge 4 ]; then
break
fi
running || return 1
[ "$i" -ge 4 ] && [ -n "$tap" ] && [ -r "$RX" ] &&
[ "$(rx)" -ge "$((base + 4))" ] && return 0
sleep 3
done
return 0
}
running || exit 0 # guest went away before it came up
printf '%s' "$BRAND" > "$PARAM/brand_string"
echo Y > "$PARAM/cpuid_passthrough"
# initial cold boot: wait for the network, then harden
wait_net_up 0
running || exit 0
set_Y
logger -t vfio-cpuid "$DOMAIN network up: cpuid_passthrough=Y"
# every in-guest reboot fires a QEMU RESET: drop to N for the re-enumeration, then
# raise it again once the guest's NIC is back. --loop streams one line per reset.
$V qemu-monitor-event --domain "$DOMAIN" --event RESET --loop 2>/dev/null | while read -r _; do
running || continue
base=$(rx)
set_N
logger -t vfio-cpuid "$DOMAIN reset: cpuid_passthrough=N for re-enumeration"
wait_net_up "$base" || continue
running || continue
set_Y
logger -t vfio-cpuid "$DOMAIN back up: cpuid_passthrough=Y"
done

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@@ -57,6 +57,24 @@ group_members() {
done
}
# The functions to hand to the guest with GPU $1: every device in its IOMMU group
# (mandatory for vfio), plus any sibling function of the same PCI device that is
# itself a display or HDMI/DP audio controller. An APU parks its PSP and USB
# controllers on the same PCI device in separate IOMMU groups - those are the
# host's, so siblings are filtered by class and never pulled in blindly.
passthrough_devs() {
local d="$1" m cls
{
group_members "$d"
for m in "/sys/bus/pci/devices/${d%.*}".*; do
[ -e "$m" ] || continue
m=$(basename "$m")
cls=$(cat "/sys/bus/pci/devices/$m/class" 2>/dev/null)
case "$cls" in 0x03*|0x0403*) echo "$m";; esac
done
} | sort -u
}
driver_of() {
local l
l=$(readlink -f "/sys/bus/pci/devices/$1/driver" 2>/dev/null)
@@ -79,7 +97,7 @@ drives_display() {
ids_of() { # vendor:device for vfio-pci binding
local d
for d in $(group_members "$1"); do
for d in $(passthrough_devs "$1"); do
local cls; cls=$(cat "/sys/bus/pci/devices/$d/class" 2>/dev/null)
# only real functions of the card: skip bridges (class 0x0604xx)
case "$cls" in 0x0604*) continue;; esac
@@ -219,7 +237,7 @@ prepare)
# 1. stop whatever is holding the DRM device
dm=$(systemctl list-units --type=service --state=running --no-legend 2>/dev/null |
awk '{print $1}' | grep -xE '(gdm|sddm|lightdm|lxdm|greetd|display-manager)\.service' | head -1)
awk '{print $1}' | grep -xE '((gdm|sddm|lightdm|lxdm|greetd|ly|emptty|lemurs)(@[a-z0-9-]+)?|display-manager)\.service' | head -1)
if [ -n "$dm" ]; then
echo "$dm" > "$STATE/dm"
log "stopping $dm"
@@ -303,7 +321,7 @@ apply() {
"$v" -c qemu:///system dumpxml --inactive "$dom" > "$backup/$dom.gpu-current.xml"
grep -q 'ua-vfionative-gpu' "$backup/$dom.gpu-current.xml" || cp "$backup/$dom.gpu-current.xml" "$backup/$dom.before-gpu.xml"
local devs="" m
for m in $( { group_members "$d"; ls -d "/sys/bus/pci/devices/${d%.*}".* | xargs -n1 basename; } | sort -u); do
for m in $(passthrough_devs "$d"); do
case "$(cat "/sys/bus/pci/devices/$m/class" 2>/dev/null)" in 0x0604*) continue;; esac
IFS=':.' read -r dm bs sl fn <<< "$m"
devs+=" <hostdev mode='subsystem' type='pci' managed='yes'>\n <source>\n"
@@ -330,7 +348,7 @@ xml() {
echo "Add this to the domain, inside <devices>. Every device in the GPU's"
echo "IOMMU group has to go together:"
echo
for m in $(group_members "$d"); do
for m in $(passthrough_devs "$d"); do
local cls; cls=$(cat "/sys/bus/pci/devices/$m/class" 2>/dev/null)
case "$cls" in 0x0604*) continue;; esac
IFS=':. ' read -r dom bus slot fn <<< "$(echo "$m" | tr ':.' ' ')"

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@@ -0,0 +1,15 @@
#!/bin/bash
# libvirt qemu hook: turn GSO and GRO on for the guest's tap.
#
# QEMU leaves them off and sets the tap up after udev has run, so it has to
# happen here. Paired with MTU 9000 they are the difference between 2.5 and
# 14 Gbit/s into the guest; neither helps alone. Tap names come from the domain
# XML on stdin, so the hook never calls virsh, which would deadlock libvirtd.
[ "$2" = started ] || exit 0
for tap in $(grep -oE "<target dev='(vnet|tap|macvtap)[^']*'" | sed "s/.*dev='//; s/'$//"); do
ethtool -K "$tap" gso on gro on 2>/dev/null
done
exit 0

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@@ -637,8 +637,11 @@ if conformant and E["CONVERT"] == "1":
if "device='disk'" not in d or ("bus='nvme'" in d and "<serial>" in d):
return d
d = re.sub(r"<target dev='([^']*)' bus='(virtio|sata|scsi)'/>", r"<target dev='\1' bus='nvme'/>", d)
# cache='none' is O_DIRECT: on btrfs the guest can change a page while the
# write is in flight, so the stored checksum never matches and later reads
# fail with EIO. Buffered writes hand the filesystem a stable page.
d = re.sub(r"<driver name='qemu' type='([^']*)'[^/]*/>",
r"<driver name='qemu' type='\1' cache='none' io='native' discard='unmap'/>", d)
r"<driver name='qemu' type='\1' cache='writeback' io='threads' discard='unmap'/>", d)
d = re.sub(r"\s*<address type='(pci|drive)'[^/]*/>", "", d)
if "<serial>" not in d:
serial = E["NVME_SERIAL"] if n[0] == 0 else E["NVME_SERIAL"][:-1] + "0123456789ABCDEF"[n[0] % 16]
@@ -658,7 +661,11 @@ if conformant and E["CONVERT"] == "1":
s = re.sub(r"\s*<input type='[^']*' bus='virtio'/>", "", s)
s = re.sub(r"<memballoon model='virtio'>.*?</memballoon>", "<memballoon model='none'/>", s, flags=re.S)
s = re.sub(r"<memballoon model='virtio'/>", "<memballoon model='none'/>", s)
s = re.sub(r"<model type='virtio'/>(\s*<driver [^/]*/>)?", "<model type='e1000e'/>", s)
# jumbo frames are the single biggest win on the host<->guest link: the emulated
# NIC is packet-rate bound, so 9000-byte frames cut the per-packet cost the guest
# pays on receive. Measured 2922 -> 14232 Mbit/s inbound on igb, byte-exact clean.
s = re.sub(r"<model type='virtio'/>(\s*<driver [^/]*/>)?",
"<model type='igb'/>\n <mtu size='9000'/>", s)
if prof == "full":
s = re.sub(r"<video>.*?</video>", "<video>\n <model type='none'/>\n </video>", s, flags=re.S)
@@ -824,10 +831,19 @@ if [ "$PROFILE" = full ]; then
fi
if [ ! -e /usr/lib/udev/rules.d/99-vfio-native-vnet-offload.rules ] && [ ! -e /etc/udev/rules.d/99-vfio-native-vnet-offload.rules ]; then
echo "NOTE: the e1000e offload udev rule is not installed. SSH into the guest will fail with"
echo "NOTE: the NIC offload udev rule is not installed. SSH into the guest will fail with"
echo " 'Corrupted MAC on input' until it is:"
echo " sudo install -Dm644 $SELF/scripts/99-vfio-native-vnet-offload.rules /etc/udev/rules.d/ && sudo udevadm control --reload-rules"
fi
NET=$("${C[@]}" dumpxml "$DOM" 2>/dev/null | sed -n "s/.*<source network='\([^']*\)'.*/\1/p" | head -1)
NETMTU=$([ -n "$NET" ] && "${C[@]}" net-dumpxml --inactive "$NET" 2>/dev/null | sed -n "s/.*<mtu size='\([0-9]*\)'.*/\1/p")
if [ -n "$NET" ] && [ "${NETMTU:-1500}" -lt 9000 ]; then
echo "NOTE: the guest interface asks for MTU 9000 but libvirt network '$NET' is at ${NETMTU:-1500}."
echo " Jumbo needs both ends; inbound throughput is ~5x with it. Add <mtu size='9000'/> to"
echo " the network and restart it: virsh net-edit $NET && virsh net-destroy $NET && virsh net-start $NET"
echo " Then in the guest: set the NIC's Jumbo Packet to 9014 and the interface MTU to 9000."
fi
gov=$(cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor 2>/dev/null || echo unknown)
[ "$gov" = performance ] || echo "host governor is '$gov' - run: sudo cpupower frequency-set -g performance"