On Tue, 11 Nov 2025 13:44:23 +0100 Salvatore Bonaccorso wrote: [...] > On Wed, Nov 05, 2025 at 11:52:55PM +0100, Francesco Poli wrote: [...] > > * if I enable VT-d, audio fails to work > > > > * if I disable VT-d, audio works correctly [...] > > Now I have some questions: > > > > - is disabling VT-d in the BIOS settings equivalent to booting with > > intel_iommu=off kernel parameter? > > Yes, this result is equivalent. OK, good to know. > > > - I thought that enabling VT-d was needed for QEMU in KVM mode, but I > > cannot verify it (starting 'kvm' seems to work, without any visible > > complaint): could you please tell me what I am missing, by disabling > > VT-d? > > It depends on which use cases you have for the VMs. Do you need to > passh through hardware? Things like GPU pass-through? Do I understand correctly that it requires at least two GPUs in the box? I only have the graphics integrated in the Intel CPU, hence, if GPU pass-through indeed requires two GPUs, I am not going to need GPU pass-through anytime soon... Probably I'll never use it on this box... Is there any other relevant pass-through thing, besides GPU pass-through? > Do you use nested virtualization? VMs running within the VM which is running on the bare metal? I have never used it. I don't know whether I will need it in the future, but I guess I won't. At least, not in the short/medium term... > > > - does this additional information help in understanding the issue > > and, perhaps, in fixing it? > > That is still the harder part :(. I can imagine! :-p > We will have another meeting on > wednesday and this bug will likely (unless we run out of time) be on > the agenda/table again. Thanks a lot, this is really appreciated. > > We see more IOMMU related failures recently (when old HW is involved), > so this might indeed be the way forward, tbh. But we will see tomorrow > is someone has other input on the topic. OK, looking forward to receiving further feedback. As always, thank you so much for your kind assistance! :-) -- http://www.inventati.org/frx/ There's not a second to spare! To the laboratory! ..................................................... Francesco Poli . GnuPG key fpr == CA01 1147 9CD2 EFDF FB82 3925 3E1C 27E1 1F69 BFFE
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