Re: [PATCH v2] cpufreq: intel_pstate: Add Icelake servers support in no-HWP mode
From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Date: 2021-09-07 16:02:14
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Hi Doug, On Tue, 2021-09-07 at 08:45 -0700, Doug Smythies wrote:
Hi all, Recent ASUS BIOS updates have changed the default system response for this old thread, rendering "intel_pstate=no_hwp" useless. It also raises a question: If BIOS has forced HWP, then how do we prevent the acpi-cpufreq driver from being used? Read on.
Does BIOS has option to enable Intel speed shift with no legacy support? Then this option will not populate ACPI _PSS table.
On Fri, May 14, 2021 at 3:12 PM Doug Smythies [off-list ref] wrote:quoted
On Fri, May 14, 2021 at 1:33 PM Giovanni Gherdovich < ggherdovich@suse.cz> wrote:quoted
On Fri, 2021-05-14 at 08:31 -0700, Doug Smythies wrote:...quoted
quoted
when COMETLAKE is not in that list, can you confirm that if you go into the BIOS config at boot, and disable HWP from there, then intel_pstate does *not* load?Yes, already tested before my original reply.quoted
Does it say "intel_pstate: CPU model not supported" in the dmesg log?That I did not check, but if I boot now with an unmodified kernel 5.13-rc1 (i.e. without this patch): [ 0.369323] intel_pstate: CPU model not supportedquoted
The control may be somewhere around "power mangement" in the BIOS config, and may be called "Enable/disable Intel Speed Shift".Yes.quoted
I'm asking because I've just checked on two Dell laptops, one Skylake and the other Kabylake, and the menu is there in the BIOS config to disable HWP, but if I disable it... nothing happens. "lscpu" shows all the hwp flags as usual:Motherboard here is ASUS PRIME Z490-A. CPU: Intel(R) Core(TM) i5-10600K CPU @ 4.10GHzquoted
# lscpu | grep Flags | tr ' ' '\n' | grep hwp hwp hwp_notify hwp_act_window hwp_eppHere, for some reason I have to do it this way (sudo) or your command doesn't work properly. Results herein confirmed by looking at the "Flags" output manually without filtering: intel_speed_shift = Disabled in BIOS: doug@s19:~$ sudo lscpu | tr ' ' '\n' | grep hwp doug@s19:~$ intel_speed_shift = Auto in BIOS $ sudo lscpu | tr ' ' '\n' | grep hwp hwp hwp_notify hwp_act_window hwp_eppquoted
and turbostat gives me: # turbostat -Summary -i 1 : 2>&1 | grep MSR_PM_ENABLE cpu0: MSR_PM_ENABLE: 0x00000001 (HWP)Here: intel_speed_shift = Disabled in BIOS: root@s19:/home/doug# /home/doug/temp-k-git/linux/tools/power/x86/turbostat/turbostat -Summary -i 1 : 2>&1 | grep MSR_PM_ENABLE root@s19:/home/doug# intel_speed_shift = Auto in BIOS (the default setting) root@s19:/home/doug# /home/doug/temp-k-git/linux/tools/power/x86/turbostat/turbostat -Summary -i 1 : 2>&1 | grep MSR_PM_ENABLE cpu0: MSR_PM_ENABLE: 0x00000001 (HWP) or with "intel_pstate=no_hwp" root@s19:/home/doug# /home/doug/temp-k-git/linux/tools/power/x86/turbostat/turbostat -Summary -i 1 : 2>&1 | grep MSR_PM_ENABLE cpu0: MSR_PM_ENABLE: 0x00000000 (No-HWP)quoted
Which is to say, on the Intel client machines I have, the firmware doesn't seem to be able to hide HWP from the OS. Buggy BIOS? Maybe, the fact of the matter is, I wouldn't need to add, say, KABYLAKE to that list, based on my experience.My experience (hardware) differs from yours with respect to this.quoted
The other side of the issue is that, from my understanding, the preferred/supported way to disable HWP is to boot with intel_pstate=no_hwp,Previous correspondence was with BIOS version 1003. There have been 3 BIOS releases since then (at least that I know of), 2103, 2201, 2301, and all of them have changed the behaviour of the "Auto" setting for Intel Speed Shift Technology BIOS setting, forcing it on upon transfer of control to the OS. Where with "intel_pstate=no_hwp" one used to get 0 for MSR_PM_ENABLE (0x770) they now get 1.
So they are forcing Out of band OOB mode. Does bit 8 or 18 in MSR 0x1aa is set? Thanks, Srinivas
quoted hunk ↗ jump to hunk
That was for my ASUS Z490-P Motherboard. For my ASUS Z390-A Motherboard (actually a windows 10 computer now), with an older BIOS, things still work properly for "intel_pstate=no_hwp", and while there is a newer BIOS, I will not install it as it is also not possible to rollback. I have had an escalation in progress with ASUS about this for about a month, and while they have been responsive we have communications/language issues and have yet to even agree that there is an issue. I have been working with this incomplete patch:diff --git a/drivers/cpufreq/intel_pstate.cb/drivers/cpufreq/intel_pstate.c index bb4549959b11..7dcc51ee56ea 100644--- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c@@ -3347,17 +3347,27 @@ device_initcall(intel_pstate_init);static int __init intel_pstate_setup(char *str) { + /* The following needs to be conditional on CPUID with EAX 6 */ + /* CPUID.06H:EAX[bit 7], which I do not know how to do. */ + /* Avoid doing checking and printing multiple times, */ + /* which I do not know why it does. */ + if(!force_load){ + if(intel_pstate_hwp_is_enabled()){ + pr_info("HWP enabled by BIOS\n"); + force_load = 1; + } + } if (!str) return -EINVAL; - if (!strcmp(str, "disable")) + if (!strcmp(str, "disable") && !force_load) no_load = 1; - else if (!strcmp(str, "active")) + if (!strcmp(str, "active") && !no_load) default_driver = &intel_pstate; else if (!strcmp(str, "passive")) default_driver = &intel_cpufreq; - if (!strcmp(str, "no_hwp")) { + if (!strcmp(str, "no_hwp") && !force_load) { pr_info("HWP disabled\n"); no_hwp = 1; } Which has troubles when HWP has been disabled by BIOS, but otherwise works well. HWP Disabled by BIOS: doug@s19:~$ sudo dmesg | grep intel_pstate [sudo] password for doug: [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-ipstate4 root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=314 intel_pstate=active intel_pstate=no_hwp msr.allow_writes=on cpuidle.governor=teo [ 0.000000] intel_pstate_setup+0x24/0x151 [ 0.000000] intel_pstate_setup+0x24/0x151 [ 0.000000] intel_pstate: HWP disabled [ 0.051278] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-ipstate4 root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=314 intel_pstate=active intel_pstate=no_hwp msr.allow_writes=on cpuidle.governor=teo [ 0.393236] intel_pstate: Intel P-state driver initializing HWP force enabled by BIOS, which is the only other option with the newer BIOS: doug@s19:~$ sudo dmesg | grep intel_pstate [sudo] password for doug: [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-ipstate4 root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=314 intel_pstate=active intel_pstate=no_hwp msr.allow_writes=on cpuidle.governor=teo [ 0.000000] intel_pstate: HWP enabled by BIOS [ 0.049205] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-ipstate4 root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=314 intel_pstate=active intel_pstate=no_hwp msr.allow_writes=on cpuidle.governor=teo [ 0.370662] intel_pstate: Intel P-state driver initializing [ 0.371590] intel_pstate: HWP enabled HWP forced by BIOS, disable intel_pstate: doug@s19:~$ sudo dmesg | grep intel_pstate [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-ipstate4 root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=300 intel_pstate=disable msr.allow_writes=on cpuidle.governor=teo [ 0.000000] intel_pstate: HWP enabled by BIOS [ 0.049133] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-ipstate4 root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=300 intel_pstate=disable msr.allow_writes=on cpuidle.governor=teo [ 0.370519] intel_pstate: Intel P-state driver initializing [ 0.371451] intel_pstate: HWP enabled doug@s19:~$ cat /sys/devices/system/cpu/cpu5/cpufreq/scaling_driver intel_pstate HWP forced by BIOS, disable intel_pstate:, unpatched kernel 5.14: doug@s19:~$ sudo dmesg | grep intel_pstate [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-stock root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=300 intel_pstate=disable msr.allow_writes=on cpuidle.governor=teo [ 0.049108] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.14.0-stock root=UUID=0ac356c1-caa9-4c2e-8229-4408bd998dbd ro ipv6.disable=1 consoleblank=300 intel_pstate=disable msr.allow_writes=on cpuidle.governor=teo doug@s19:~$ cat /sys/devices/system/cpu/cpu5/cpufreq/scaling_driver acpi-cpufreq doug@s19:~$ sudo rdmsr 0x770 1 Observe the driver ended up as acpi-cpufreq, but with HWP enabled. ... Doug