Am 05.09.25 um 4:15 PM schrieb Daniel Kral:
> Since QEMU 9.2 [0], the default I/O address space bit width was raised
> from 39 bits to 48 bits for the Intel vIOMMU driver, which makes the
> aw-bits check introduced in [1] to trip for host CPUs with less than 48
> bits physical address width from QEMU 9.2 onwards:
>
> vfio 0000:XX:YY.Z: Failed to set vIOMMU: aw-bits 48 > host aw-bits 39
>
> For VFIO devices where a vIOMMU is in-use, QEMU fetches the IOVA ranges
> with the iommufd ioctl IOMMU_IOAS_IOVA_RANGES or the vfio_iommu_type1's
> VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE info, so 'phys-bits' doesn't change
> the behavior of the check.
>
> Therefore, expose the 'aw-bits' option of the intel-iommu and
> virtio-iommu QEMU drivers to allow users to set the value.
>
> [0] qemu ddd84fd0c1 ("intel_iommu: Set default aw_bits to 48 starting from
> QEMU 9.2")
> [1] qemu 77f6efc0ab ("intel_iommu: Check compatibility with host IOMMU
> capabilities")
>
> Signed-off-by: Daniel Kral <d.k...@proxmox.com>
I'll go ahead and apply this and the below, if that addition is fine by you?
> commit 05eb8e6394ca83e53cbf6a01e1a8848ff3d4d3e8
> Author: Fiona Ebner <f.eb...@proxmox.com>
> Date: Mon Sep 8 10:37:24 2025 +0200
>
> cfg2cmd: inform users that setting guest-phys-bits might be necessary
> when setting aw-bits
>
> Until QEMU warns about this itself, inform the users here. Commit
> message below copied from [1].
>
> If a virtual machine is setup with an intel-iommu device, QEMU
> allocates and maps the (virtual) I/O address space (IOAS) for a VFIO
> passthrough device with iommufd.
>
> In case of a mismatch of the address width of the host CPU and IOMMU
> CPU, the guest physical address space (GPAS) and memory-type range
> registers (MTRRs) are setup to the host CPU's address width, which
> causes IOAS to be allocated and mapped outside of the IOMMU's maximum
> guest address width (MGAW) and causes the following error from QEMU
> (the error message is copied from the user forum [0]):
>
> kvm: vfio_container_dma_map(0x5c9222494280, 0x380000000000, 0x10000,
> 0x78075ee70000) = -22 (Invalid argument)
>
> [0]: https://forum.proxmox.com/threads/169586/page-3#post-795717
> [1]:
> https://lore.proxmox.com/pve-devel/20250902112307.124706-5-d.k...@proxmox.com/
>
> Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
> ---
> src/PVE/QemuServer.pm | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
> index c428e2d7..bf229610 100644
> --- a/src/PVE/QemuServer.pm
> +++ b/src/PVE/QemuServer.pm
> @@ -3944,7 +3944,13 @@ sub config_to_command {
>
> if (my $viommu = $machine_conf->{viommu}) {
> my $viommu_devstr = '';
> - $viommu_devstr .= ",aw-bits=$machine_conf->{'aw-bits'}" if
> $machine_conf->{'aw-bits'};
> + if ($machine_conf->{'aw-bits'}) {
> + $viommu_devstr .= ",aw-bits=$machine_conf->{'aw-bits'}";
> +
> + # TODO remove message once this gets properly checked/warned
> about in QEMU itself.
> + print "vIOMMU 'aw-bits' set to $machine_conf->{'aw-bits'}.
> Sometimes it is necessary to"
> + . " set the CPU's 'guest-phys-bits' to the same value.\n";
> + }
>
> if ($viommu eq 'intel') {
> $viommu_devstr =
> "intel-iommu,intremap=on,caching-mode=on$viommu_devstr";
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