On 06.08.2025 12:23, Marek Marczykowski-Górecki wrote: > We've got several reports that S3 reliability recently regressed. We > identified it's definitely related to XSA-471 patches, and bisection > points at "x86/idle: Remove broken MWAIT implementation". I don't have > reliable reproduction steps, so I'm not 100% sure if it's really this > patch, or maybe an earlier one - but it's definitely already broken at > this point in the series. Most reports are about Xen 4.17 (as that's > what stable Qubes OS version currently use), but I think I've seen > somebody reporting the issue on 4.19 too (but I don't have clear > evidence, especially if it's the same issue).
At the time we've been discussing the explicit raising of TIMER_SOFTIRQ in mwait_idle_with_hints() a lot. If it was now truly missing, that imo shouldn't cause problems only after resume, but then it may have covered for some omission during resume. As a far-fetched experiment, could you try putting that back (including the calculation of the "expires" local variable)? Jan
