The recent hypercall page changes breaks dom0=pvh on 6.12.6. When booting with dom0=pvh, 6.12.6 reboots a second after Xen hands off control. dom0=pv boots properly, but dom0=pvh does not. A bisection indicates that commit f7c3fdad0a474062d566aae3289d490d7e702d30 (x86/xen: don't do PV iret hypercall through hypercall page) works, but commit 42d50bb38a691ea8ac459b4f966f7e66f939c147 (x86/xen: use new hypercall functions instead of hypercall page) does not boot. panic=0, xen noreboot, earlyprintk=xen are not sufficient for debugging the problem, so it appears to happen very early, which aligns with changes that are as fundamental like hypercalls.
Xen version: 4.19.0 (from Fedora 41) Kernel version: 6.12.6
This issue has been reproduced on the following setups: - A desktop system with an Intel i9-14900KS / external NVIDIA GPU (not in use) - A server system with an Intel E5-2660 v4 (512GB of RAM, blade system) This indicates the problem is widespread.
Testing indicates that the crash happens in __static_call_update_early Confirmed that domU PVH works fine, but dom0 PVH is broken.