[pve-devel] [PATCH qemu-server 3/3] fix #2794: allow legacy IGD passthrough

[Thomas Lamprecht]

Am 6/18/20 um 4:36 PM schrieb Stefan Reiter:
> Legacy IGD passthrough requires address 00:1f.0 to not be assigned to
> anything on QEMU startup (currently it's assigned to bridge pci.2).
> Changing this in general would break live-migration, so introduce a new
> hostpci parameter "legacy-igd", which if set to 1 will move that bridge
> to be nested under bridge 1.
> 
> This is safe because:
> * Bridge 1 is unconditionally created on i440fx, so nesting is ok
> * Defaults are not changed, i.e. PCI layout only changes when the new
> parameter is specified manually
> * hostpci forbids migration anyway
> 
> Additionally, the PT device has to be assigned address 00:02.0 in the
> guest as well, which is usually used for VGA assignment. Luckily, IGD PT
> requires vga=none, so that is not an issue either.
> 
> See https://git.qemu.org/?p=qemu.git;a=blob;f=docs/igd-assign.txt
> 
> Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
> ---
>  PVE/QemuServer.pm     | 10 ++++++++--
>  PVE/QemuServer/PCI.pm | 45 +++++++++++++++++++++++++++++++++++++------
>  2 files changed, 47 insertions(+), 8 deletions(-)
> 
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index 1c08222..1abe64b 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -3102,7 +3102,7 @@ sub config_to_command {
>      }
>  
>      # host pci device passthrough
> -    my ($kvm_off, $gpu_passthrough) = PVE::QemuServer::PCI::print_hostpci_devices(
> +    my ($kvm_off, $gpu_passthrough, $legacy_igd) = PVE::QemuServer::PCI::print_hostpci_devices(
>  	$conf, $devices, $winversion, $q35, $bridges, $arch, $machine_type);
>  
>      # usb devices
> @@ -3458,7 +3458,13 @@ sub config_to_command {
>  
>      for my $k (sort {$b cmp $a} keys %$bridges) {
>  	next if $q35 && $k < 4; # q35.cfg already includes bridges up to 3
> -	$pciaddr = print_pci_addr("pci.$k", undef, $arch, $machine_type);
> +
> +	my $k_name = $k;
> +	if ($k == 2 && $legacy_igd) {
> +	    $k_name = "$k-igd";
> +	}
> +	$pciaddr = print_pci_addr("pci.$k_name", undef, $arch, $machine_type);
> +

ugh, hacks all the way down, but well it seems that pass through stuff relies on that -.-

>  	my $devstr = "pci-bridge,id=pci.$k,chassis_nr=$k$pciaddr";
>  	if ($q35) {
>  	    # add after -readconfig pve-q35.cfg
> diff --git a/PVE/QemuServer/PCI.pm b/PVE/QemuServer/PCI.pm
> index 39f9970..e835f39 100644
> --- a/PVE/QemuServer/PCI.pm
> +++ b/PVE/QemuServer/PCI.pm
> @@ -55,6 +55,14 @@ EODESCR
>  	optional => 1,
>  	default => 0,
>      },
> +    'legacy-igd' => {
> +	type => 'boolean',
> +	description => "Pass this device in legacy IGD mode (allows required"
> +		     . " 1f.0 PCI bridge and assigns correct address)."
> +		     . " Requires i440fx machine type and VGA set to 'none'.",

I'd rather use 100 cc lines for that and do not align subsequent concatenated lines indentation
but just indent them 4 spaces more than the prev level.

> +	optional => 1,
> +	default => 0,
> +    },
>      'mdev' => {
>  	type => 'string',
>          format_description => 'string',
> @@ -89,7 +97,8 @@ sub get_pci_addr_map {
>      $pci_addr_map = {
>  	piix3 => { bus => 0, addr => 1, conflict_ok => qw(ehci)  },
>  	ehci => { bus => 0, addr => 1, conflict_ok => qw(piix3) }, # instead of piix3 on arm
> -	vga => { bus => 0, addr => 2 },
> +	vga => { bus => 0, addr => 2, conflict_ok => qw(legacy-igd) },

sorry, but how do they conflict? the address differs so the check can't hit.
Or is this just for documentation purpose?

> +	'legacy-igd' => { bus => 0, addr => 2, conflict_ok => qw(vga) }, # legacy-igd requires vga=none
>  	balloon0 => { bus => 0, addr => 3 },
>  	watchdog => { bus => 0, addr => 4 },
>  	scsihw0 => { bus => 0, addr => 5, conflict_ok => qw(pci.3) },
> @@ -149,6 +158,7 @@ sub get_pci_addr_map {
>  	'xhci' => { bus => 1, addr => 27 },
>  	'pci.4' => { bus => 1, addr => 28 },
>  	'rng0' => { bus => 1, addr => 29 },
> +	'pci.2-igd' => { bus => 1, addr => 30 }, # replaces pci.2 in case a legacy IGD device is passed through
>  	'virtio6' => { bus => 2, addr => 1 },
>  	'virtio7' => { bus => 2, addr => 2 },
>  	'virtio8' => { bus => 2, addr => 3 },
> @@ -351,6 +361,7 @@ sub print_hostpci_devices {
>  
>      my $kvm_off = 0;
>      my $gpu_passthrough = 0;
> +    my $legacy_igd = 0;
>  
>      for (my $i = 0; $i < $MAX_HOSTPCI_DEVICES; $i++)  {
>  	my $id = "hostpci$i";
> @@ -372,7 +383,32 @@ sub print_hostpci_devices {
>  		$pciaddr = print_pcie_addr($id);
>  	    }
>  	} else {
> -	    $pciaddr = print_pci_addr($id, $bridges, $arch, $machine_type);
> +	    my $pci_name = $d->{'legacy-igd'} ? 'legacy-igd' : $id;
> +	    $pciaddr = print_pci_addr($pci_name, $bridges, $arch, $machine_type);
> +	}
> +
> +	my $pcidevices = $d->{pciid};
> +	my $multifunction = 1 if @$pcidevices > 1;
> +
> +	if ($d->{'legacy-igd'}) {
> +	    die "only one device can be assigned in legacy-igd mode\n"
> +		if $legacy_igd;
> +	    $legacy_igd = 1;
> +
> +	    die "legacy IGD assignment requires VGA mode to be 'none'\n"
> +		if !defined($conf->{'vga'}) || $conf->{'vga'} ne 'none';
> +	    die "legacy IGD assignment requires rombar to be enabled\n"
> +		if defined($d->{rombar}) && !$d->{rombar};
> +	    die "legacy IGD assignment is not compatible with x-vga\n"
> +		if $d->{'x-vga'};
> +	    die "legacy IGD assignment is not compatible with mdev\n"
> +		if $d->{mdev};
> +	    die "legacy IGD assignment is not compatible with q35\n"
> +		if $q35;
> +	    die "legacy IGD assignment is not compatible with multifunction devices\n"
> +		if $multifunction;
> +	    die "legacy IGD assignment only works for devices on host bus 00:02.0\n"
> +		if $pcidevices->[0]->{id} !~ m/02\.0$/;
>  	}
>  
>  	my $xvga = '';
> @@ -383,9 +419,6 @@ sub print_hostpci_devices {
>  	    $gpu_passthrough = 1;
>  	}
>  
> -	my $pcidevices = $d->{pciid};
> -	my $multifunction = 1 if @$pcidevices > 1;
> -
>  	my $sysfspath;
>  	if ($d->{mdev} && scalar(@$pcidevices) == 1) {
>  	    my $pci_id = $pcidevices->[0]->{id};
> @@ -420,7 +453,7 @@ sub print_hostpci_devices {
>  	}
>      }
>  
> -    return ($kvm_off, $gpu_passthrough);
> +    return ($kvm_off, $gpu_passthrough, $legacy_igd);
>  }
>  
>  1;
>