Public bug reported: This is a public version of: https://bugs.launchpad.net/bugs/2078894
[Impact] In Emerald Rapids VMs, a stack trace is printed during boot on 6.8 based kernels. The stack traces look like: [ 1.206658] intel_pstate: Intel P-state driver initializing [ 1.207453] unchecked MSR access error: WRMSR to 0x199 (tried to write 0x0000000000000800) at rIP: 0xffffffffb94c3b24 (native_write_msr+0x4/0x40) [ 1.208422] Call Trace: [ 1.208422] <TASK> [ 1.208422] ? show_stack_regs+0x23/0x40 [ 1.208422] ? ex_handler_msr+0x10a/0x180 [ 1.208422] ? fixup_exception+0x183/0x390 [ 1.208422] ? gp_try_fixup_and_notify+0x23/0xc0 [ 1.208422] ? exc_general_protection+0x15e/0x480 [ 1.208422] ? asm_exc_general_protection+0x27/0x30 [ 1.208422] ? __pfx___wrmsr_on_cpu+0x10/0x10 [ 1.208422] ? native_write_msr+0x4/0x40 [ 1.208422] ? __wrmsr_on_cpu+0x4b/0x90 [ 1.208422] ? __pfx___rdmsr_on_cpu+0x10/0x10 [ 1.208422] ? __pfx___wrmsr_on_cpu+0x10/0x10 [ 1.208422] generic_exec_single+0x7e/0x120 [ 1.208422] smp_call_function_single+0x103/0x140 [ 1.208422] ? __pfx___wrmsr_on_cpu+0x10/0x10 [ 1.208422] wrmsrl_on_cpu+0x57/0x80 [ 1.208422] intel_pstate_set_pstate+0x3e/0x80 [ 1.208422] intel_pstate_get_cpu_pstates.constprop.0+0xd7/0x190 [ 1.208422] intel_pstate_init_cpu+0x3f/0x140 [ 1.208422] intel_cpufreq_cpu_init+0x44/0x270 [ 1.208422] ? freq_qos_add_notifier+0x45/0x80 [ 1.208422] cpufreq_online+0x444/0xb80 [ 1.208422] cpufreq_add_dev+0x99/0xd0 [ 1.208422] subsys_interface_register+0x11c/0x140 [ 1.208422] cpufreq_register_driver+0x1b5/0x330 [ 1.208422] intel_pstate_register_driver+0x48/0xd0 [ 1.208422] intel_pstate_init+0x25c/0x810 [ 1.208422] ? __pfx_intel_pstate_init+0x10/0x10 [ 1.208422] do_one_initcall+0x5b/0x310 [ 1.208422] do_initcalls+0x104/0x210 [ 1.208422] ? __pfx_kernel_init+0x10/0x10 [ 1.208422] kernel_init_freeable+0x134/0x1f0 [ 1.208422] kernel_init+0x1b/0x200 [ 1.208422] ret_from_fork+0x44/0x70 [ 1.208422] ? __pfx_kernel_init+0x10/0x10 [ 1.208422] ret_from_fork_asm+0x1b/0x30 [ 1.208422] </TASK> [Fix] Cherry pick of 7e1c3f584ee7 - cpufreq: intel_pstate: Support Emerald Rapids OOB mode Upstream since v6.11. Very simple change as the OOB identifying bits are same as for the prior generation CPUs like Sapphire Rapids servers, so also add Emerald Rapids to the intel_pstate_cpu_oob_ids[] list. [Test Plan] Set HW PM OOB mode in BIOS power management config. Make sure that no cpufreq drivers are loaded. You can verify that /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver is not present or any cpufreq interface. It's also already part of linux-aws: https://bugs.launchpad.net/bugs/2078894 [Where problems could occur] cpufreq regression. ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Affects: linux (Ubuntu Noble) Importance: Undecided Assignee: Thibf (thibf) Status: New ** Also affects: linux (Ubuntu Noble) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Noble) Assignee: (unassigned) => Thibf (thibf) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2084834 Title: [SRU] cpufreq: intel_pstate: Support Emerald Rapids OOB mode To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2084834/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
