chore: release 1.3.3

README.md

@@ -165,25 +165,32 @@ vm-native-verify
 
 `vm-native-verify` also prints whether CPUID passthrough is on, which is the last step.
 
-### 6. Switch on CPUID passthrough, after every guest boot
+### 6. CPUID passthrough, on after boot and off before the next one
 
 The `TIMER` check times the world switch on an intercepted `CPUID`, and the only way to stop
-paying it is to not exit. `vm-native-setup` prints the two lines for your declared SKU; on this
+paying it is to not exit. That switch has to be off while a guest cold-boots - a booting Windows
-host they are:
+enumerates CPUID bits KVM synthesises and hangs if they vanish half way through - and on once it
+is up. Let the libvirt hook handle that around a guest:
+
+```sh
+sudo vm-native-cpuid enable win11     # off for the cold boot, on once the guest is on the network, off on stop
+sudo vm-native-cpuid status           # what is enabled, and the live switch state
+sudo vm-native-cpuid disable win11    # stop automating this guest
+sudo vm-native-cpuid revert           # remove the hook and reset the switch
+```
+
+Or drive it by hand. `vm-native-setup` prints the two lines for your declared SKU; run them once
+the guest is up, never before, and switch it off (`echo N`) before the next boot:
 
 ```sh
 echo 'AMD Ryzen 7 7700X 8-Core Processor' | sudo tee /sys/module/kvm_amd/parameters/brand_string
 echo Y | sudo tee /sys/module/kvm_amd/parameters/cpuid_passthrough
 ```
 
-Run them once the guest is up, never before: a booting Windows enumerates CPUID bits KVM
+The module applies it only to vCPU threads pinned to exactly one host CPU, so on an unpinned guest
-synthesises, and hangs if they vanish half way through. Switch it off again (`echo N`) before the
+it does nothing rather than something wrong. It is one switch and one brand string for the whole
-next boot. The module applies it only to vCPU threads pinned to exactly one host CPU, so on an
+host, so it serves one hardened guest at a time - the hook enforces that and leaves a second guest
-unpinned guest it does nothing rather than something wrong.
+alone.
-
-It is a module parameter, so it is one switch for the whole host: every pinned guest gets it, and
-a cold boot of any of them while it is on hits the race. With more than one such guest, switch it
-off before any of them boots and on again once they are all up.
 
 For the detection score, run VMAware in the guest **from the console session, not over SSH** -
 OpenSSH lands you in session 0, which is not where an interactive desktop session runs. See

docs/GUEST-SETUP.md

@@ -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
 
@@ -165,7 +164,7 @@ echo Y | sudo tee /sys/module/kvm_amd/parameters/cpuid_passthrough
 vm-native-verify
 ```
 
-`vm-native-setup` printed those two lines with your SKU. The switch is host-wide: it applies to
+`vm-native-setup` printed those two lines with your SKU, or `sudo vm-native-cpuid enable <domain>` does the same on/off automatically around the guest (off for the cold boot, on once its network is up). The switch is host-wide: it applies to
 every pinned guest at once, and a cold boot of any of them while it is on hits the enumeration
 race, so with several guests turn it off before any boots and on when they are all up. Then the
 scanner, from the console session, as `docs/TESTING.md` describes. The reference guest reads 1/85.

packaging/vfio-native/.SRCINFO

@@ -1,6 +1,6 @@
 pkgbase = vfio-native
 	pkgdesc = Present a libvirt guest as a self-consistent physical machine, and tune it
-	pkgver = 1.1.0
+	pkgver = 1.3.3
 	pkgrel = 1
 	url = https://git.archworks.co/sandwich/vfio-native
 	install = vfio-native.install
@@ -17,7 +17,7 @@ pkgbase = vfio-native
 	optdepends = cpupower: set the host CPU governor
 	optdepends = vfio-native-kvm-dkms: patched KVM modules for the full level
 	optdepends = vfio-native-qemu: patched QEMU for the full level
-	source = git+https://git.archworks.co/sandwich/vfio-native.git#tag=v1.1.0
+	source = git+https://git.archworks.co/sandwich/vfio-native.git#tag=v1.3.3
 	sha256sums = SKIP
 
 pkgname = vfio-native

packaging/vfio-native/PKGBUILD

@@ -8,7 +8,7 @@
 #   vfio-native-qemu       QEMU 11.1.1 with the platform-identity patches, in /opt
 
 pkgname=vfio-native
-pkgver=1.1.0
+pkgver=1.3.3
 pkgrel=1
 pkgdesc="Present a libvirt guest as a self-consistent physical machine, and tune it"
 arch=('any')
@@ -29,6 +29,7 @@ package() {
     install -Dm755 scripts/setup-vm.sh        "${pkgdir}/usr/bin/vm-native-setup"
     install -Dm755 scripts/verify-perf.sh     "${pkgdir}/usr/bin/vm-native-verify"
     install -Dm755 scripts/gpu-passthrough.sh "${pkgdir}/usr/bin/vm-native-gpu"
+    install -Dm755 scripts/cpuid-passthrough.sh "${pkgdir}/usr/bin/vm-native-cpuid"
 
     local share="${pkgdir}/usr/share/vfio-native"
     install -Dm644 bench/vmbench.c    "${share}/bench/vmbench.c"
@@ -36,6 +37,8 @@ package() {
     install -Dm755 scripts/install-modules.sh   "${share}/scripts/install-modules.sh"
     install -Dm755 scripts/restore-stock-kvm.sh "${share}/scripts/restore-stock-kvm.sh"
     install -Dm755 scripts/generate-tables.py   "${share}/scripts/generate-tables.py"
+    install -Dm755 scripts/libvirt-hook-cpuid-passthrough.sh "${share}/scripts/libvirt-hook-cpuid-passthrough.sh"
+    install -Dm755 scripts/cpuid-passthrough-watch          "${share}/scripts/cpuid-passthrough-watch"
     install -Dm644 -t "${share}/acpi" acpi/*.aml acpi/*.dsl
     install -dm755 "${share}/patches"
     cp -r patches/. "${share}/patches/"
@@ -45,7 +48,6 @@ package() {
     # this coexists with whatever hook the host already has.
     install -Dm755 scripts/libvirt-hook-cpu-isolation.sh \
         "${pkgdir}/etc/libvirt/hooks/qemu.d/10-cpu-isolation.sh"
-    # e1000e offloads corrupt integrity-checked traffic on libvirt taps; host-wide by nature
+    install -Dm755 scripts/libvirt-hook-vnet-offload.sh \
-    install -Dm644 scripts/99-vfio-native-vnet-offload.rules \
+        "${pkgdir}/etc/libvirt/hooks/qemu.d/20-vnet-offload.sh"
-        "${pkgdir}/usr/lib/udev/rules.d/99-vfio-native-vnet-offload.rules"
 }

packaging/vfio-native/vfio-native.install

@@ -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
+  A hook at /etc/libvirt/hooks/qemu.d/20-vnet-offload.sh turns GSO and GRO on
-  libvirt tap as it appears. The emulated e1000e NIC corrupts integrity-checked
+  for the guest's tap. With the interface's MTU 9000 that takes the inbound link
-  traffic with them on; SSH to the guest fails with "Corrupted MAC on input".
+  from 2.9 to 14 Gbit/s; neither does anything alone. The libvirt network needs
-  It applies to every VM on the host; the throughput cost on a host<->guest
+  <mtu size='9000'/> too, and the guest needs Jumbo Packet 9014 with its
-  link is not measurable.
+  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,

scripts/99-vfio-native-vnet-offload.rules

@@ -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"

scripts/cpuid-passthrough-watch

@@ -0,0 +1,71 @@
+#!/bin/bash
+# Keeps the kvm_amd cpuid_passthrough switch correct across a guest's whole life,
+# in-guest reboots included.
+#
+# 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).
+
+DOMAIN=$1
+BRAND=$2
+PARAM=/sys/module/kvm_amd/parameters
+V="virsh -c qemu:///system"
+
+running() { [ "$($V domstate "$DOMAIN" 2>/dev/null)" = running ]; }
+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 || return 1
+        [ "$i" -ge 4 ] && [ -n "$tap" ] && [ -r "$RX" ] &&
+            [ "$(rx)" -ge "$((base + 4))" ] && return 0
+        sleep 3
+    done
+    return 0
+}
+
+# The hook arms this watcher at prepare, before QEMU starts, so the domain is not
+# yet running and its tap does not exist. Wait for the domain, then read the tap;
+# otherwise the first running check in wait_net_up bails and the flip never happens.
+for _ in $(seq 1 120); do running && break; sleep 1; done
+running || exit 0
+tap=$($V domiflist "$DOMAIN" 2>/dev/null | awk '$1 ~ /^(vnet|tap|macvtap)/ {print $1; exit}')
+RX="/sys/class/net/$tap/statistics/rx_packets"
+
+# 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

scripts/cpuid-passthrough.sh

@@ -0,0 +1,77 @@
+#!/bin/bash
+# vm-native-cpuid - manage the automatic cpuid_passthrough toggle for hardened guests.
+#
+#   vm-native-cpuid enable <domain>    apply the automatic cpuid passthrough to <domain>
+#   vm-native-cpuid disable <domain>   stop applying it to <domain>
+#   vm-native-cpuid status             show the config and the live module state
+#   vm-native-cpuid revert             remove the hook, watcher and config; reset the module
+#
+# The switch and brand string are one global kvm_amd parameter, so it serves one
+# hardened guest at a time. It is off until you enable it here - no domain is
+# touched otherwise. Around an enabled guest the libvirt hook forces the switch off
+# for the cold boot, a watcher flips it on once the guest's network is up, and it
+# goes off again on stop.
+
+set -uo pipefail
+
+CONF=/etc/vfio-native/cpuid-passthrough.conf
+HOOK=/etc/libvirt/hooks/qemu.d/30-cpuid-passthrough.sh
+WATCH=/usr/lib/vfio-native/cpuid-passthrough-watch
+PARAM=/sys/module/kvm_amd/parameters
+SELF=$(cd "$(dirname "$0")/.." 2>/dev/null && pwd)
+
+die() { echo "$*" >&2; exit 1; }
+need_root() { [ "$(id -u)" = 0 ] || die "run this as root"; }
+
+load() { ENABLED=yes; DOMAINS=""; [ -r "$CONF" ] && . "$CONF"; }
+save() { mkdir -p "$(dirname "$CONF")"; printf 'ENABLED=%s\nDOMAINS="%s"\n' "$ENABLED" "$DOMAINS" > "$CONF"; }
+
+# copy the hook and watcher into place from the installed tree or this checkout
+install_hook() {
+    local src=""
+    for d in /usr/share/vfio-native "$SELF"; do
+        [ -f "$d/scripts/libvirt-hook-cpuid-passthrough.sh" ] && src="$d"
+    done
+    [ -n "$src" ] || die "cannot find the hook source (install vfio-native, or run from a checkout)"
+    install -Dm755 "$src/scripts/libvirt-hook-cpuid-passthrough.sh" "$HOOK"
+    install -Dm755 "$src/scripts/cpuid-passthrough-watch"          "$WATCH"
+}
+
+case "${1:-}" in
+enable)
+    need_root; [ -n "${2:-}" ] || die "usage: vm-native-cpuid enable <domain>"
+    load; install_hook; ENABLED=yes
+    case " $DOMAINS " in *" $2 "*) ;; *) DOMAINS="${DOMAINS:+$DOMAINS }$2" ;; esac
+    save
+    echo "$2 enabled. cpuid passthrough is now automatic for: $DOMAINS"
+    echo "on start it forces N for the cold boot, flips Y once the guest is on the network, N again on stop."
+    ;;
+disable)
+    need_root; [ -n "${2:-}" ] || die "usage: vm-native-cpuid disable <domain>"
+    load; DOMAINS=$(printf ' %s ' "$DOMAINS" | sed "s/ $2 / /g" | xargs || true); save
+    systemctl stop "vfio-cpuid-watch-$2.service" 2>/dev/null || true
+    echo "$2 disabled. remaining: ${DOMAINS:-none}"
+    ;;
+status)
+    load
+    echo "config:  $CONF"
+    echo "enabled: $ENABLED"
+    echo "domains: ${DOMAINS:-none}"
+    echo "hook:    $([ -f "$HOOK" ] && echo installed || echo 'not installed')"
+    if [ -r "$PARAM/cpuid_passthrough" ]; then
+        echo "module:  cpuid_passthrough=$(cat "$PARAM/cpuid_passthrough") brand='$(cat "$PARAM/brand_string")'"
+    else
+        echo "module:  patched kvm_amd not loaded"
+    fi
+    ;;
+revert)
+    need_root; load
+    for d in $DOMAINS; do systemctl stop "vfio-cpuid-watch-$d.service" 2>/dev/null || true; done
+    rm -f "$HOOK" "$WATCH" "$CONF" /run/vfio-native/cpuid-active
+    [ -w "$PARAM/cpuid_passthrough" ] && echo N > "$PARAM/cpuid_passthrough"
+    echo "reverted: hook, watcher and config removed; cpuid_passthrough=N."
+    ;;
+*)
+    sed -n '2,13p' "$0" | sed 's/^#\( \|$\)//'
+    ;;
+esac

scripts/gpu-passthrough.sh

@@ -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 ':.' '  ')"

scripts/libvirt-hook-cpuid-passthrough.sh

@@ -0,0 +1,68 @@
+#!/bin/bash
+# libvirt qemu hook: drive the kvm_amd cpuid_passthrough switch around a guest's life.
+#
+# The switch must be OFF while a guest cold-boots - raw CPUID changes shape mid
+# enumeration and Windows hangs - and ON once the guest is up, where it clears the
+# TIMER detection. This applies only to the domains you opt in with
+# `vm-native-cpuid enable <domain>`; it does nothing to any other guest.
+#
+# On start it sets the brand string from the guest's declared SKU and forces N,
+# then a detached watcher flips Y once the guest's network is up; on stop it sets N.
+# cpuid_passthrough and brand_string are one global kvm_amd parameter, so a single
+# hardened guest is served at a time; a second is logged and left alone.
+#
+# Exits 0 on every path. The hook never calls virsh (that deadlocks libvirtd); the
+# watcher that does is a transient systemd unit and runs after this returns.
+
+CONF=/etc/vfio-native/cpuid-passthrough.conf
+ENABLED=yes
+DOMAINS=""
+[ -r "$CONF" ] && . "$CONF"
+[ "$ENABLED" = yes ] || exit 0
+
+PARAM=/sys/module/kvm_amd/parameters
+[ -w "$PARAM/cpuid_passthrough" ] || exit 0    # stock module, or not an AMD host
+
+DOMAIN=$1
+OPERATION=$2
+case " $DOMAINS " in *" $DOMAIN "*) ;; *) exit 0 ;; esac    # not an opted-in domain
+
+RUN=/run/vfio-native
+ACTIVE=$RUN/cpuid-active
+WATCH=/usr/lib/vfio-native/cpuid-passthrough-watch
+
+case "$OPERATION" in
+prepare)
+    # the guest's declared SKU, straight from the -cpu model-id in the XML on stdin
+    BRAND=$(grep -oE "model-id=[^'\"]+" | head -1 | sed 's/^model-id=//')
+    [ -n "$BRAND" ] || exit 0                  # not a full-fidelity guest
+
+    mkdir -p "$RUN"
+    held=$( [ -e "$ACTIVE" ] && cut -d: -f1 "$ACTIVE" )
+    if [ -n "$held" ] && [ "$held" != "$DOMAIN" ]; then
+        logger -t vfio-cpuid "cpuid passthrough held by $held; $DOMAIN left unhardened (one guest at a time)"
+        exit 0
+    fi
+
+    printf '%s' "$BRAND" > "$PARAM/brand_string"
+    echo N > "$PARAM/cpuid_passthrough"         # safe for the cold boot
+    printf '%s:%s' "$DOMAIN" "$BRAND" > "$ACTIVE"
+    logger -t vfio-cpuid "$DOMAIN start: brand='$BRAND' cpuid_passthrough=N, watcher armed"
+
+    # transient systemd unit, not a bare background job: libvirt reaps anything left
+    # in the hook's own process tree; systemd-run escapes it
+    [ -x "$WATCH" ] && systemd-run --collect --quiet \
+        --unit="vfio-cpuid-watch-${DOMAIN}" "$WATCH" "$DOMAIN" "$BRAND"
+    ;;
+
+release|stopped)
+    held=$( [ -e "$ACTIVE" ] && cut -d: -f1 "$ACTIVE" )
+    [ "$held" = "$DOMAIN" ] || exit 0
+    systemctl stop "vfio-cpuid-watch-${DOMAIN}.service" 2>/dev/null
+    echo N > "$PARAM/cpuid_passthrough"
+    rm -f "$ACTIVE"
+    logger -t vfio-cpuid "$DOMAIN $OPERATION: cpuid_passthrough=N"
+    ;;
+esac
+
+exit 0

scripts/libvirt-hook-vnet-offload.sh

@@ -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

scripts/setup-vm.sh

@@ -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)
 
@@ -814,20 +821,29 @@ if [ "$PROFILE" = full ]; then
     [ "$ok" = 1 ] && echo "patched QEMU and KVM modules both in place."
     if [ -n "$MODEL" ] && [ -f /sys/module/kvm_amd/parameters/cpuid_passthrough ]; then
         echo
-        echo "The TIMER check needs CPUID passthrough, which is off by default and must be"
+        echo "The TIMER check needs CPUID passthrough, which must be off while the guest cold"
-        echo "switched on AFTER the guest has booted (it hangs a booting guest). Once the"
+        echo "boots and on once it is up. Let the hook handle that around this guest:"
-        echo "guest is up, on the host:"
+        echo "  sudo vm-native-cpuid enable $DOM"
+        echo "Or drive it by hand, after the guest has booted, on the host:"
         echo "  echo '$MODEL' | sudo tee /sys/module/kvm_amd/parameters/brand_string"
-        echo "  echo Y | sudo tee /sys/module/kvm_amd/parameters/cpuid_passthrough"
+        echo "  echo Y | sudo tee /sys/module/kvm_amd/parameters/cpuid_passthrough   # N again before the next boot"
-        echo "Switch it off again (echo N) before rebooting the guest."
     fi
 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"