Messages in this thread | | | Date | Thu, 26 Nov 2015 10:09:40 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH][v7] x86, suspend: Save/restore extra MSR registers for suspend |
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* Chen Yu <yu.c.chen@intel.com> wrote:
> A bug was reported that on certain Broadwell platforms, after resuming from S3, > the CPU is running at an anomalously low speed. > > It turns out that the BIOS has modified the value of the THERM_CONTROL register > during S3, and changed it from 0 to 0x10, thus enabled clock modulation(bit4), > but with undefined CPU Duty Cycle(bit1:3) - which causes the problem. > > Here is a simple scenario to reproduce the issue: > > 1. Boot up the system > 2. Get MSR 0x19a, it should be 0 > 3. Put the system into sleep, then wake it up > 4. Get MSR 0x19a, it shows 0x10, while it should be 0 > > Although some BIOSen want to change the CPU Duty Cycle during S3, in our case we > don't want the BIOS to do any modification. > > Fix this issue by introducing a more generic x86 framework to save/restore > specified MSR registers(THERM_CONTROL in this case) for suspend/resume. This > allows us to fix similar bugs in a much simpler way in the future. > > When the kernel wants to protect certain MSRs during suspending, we simply add a > quirk entry in msr_save_dmi_table, and customize the MSR registers inside the > quirk callback, for example: > > u32 msr_id_need_to_save[] = {MSR_ID0, MSR_ID1, MSR_ID2...}; > > and the quirk mechanism ensures that, once resumed from suspend, the MSRs > indicated by these IDs will be restored to their original, pre-suspend values. > > Since both 64-bit and 32-bit kernels are affected, this patch covers the common > 64/32-bit suspend/resume code path. And because the MSRs specified by the user > might not be available or readable in any situation, we use rdmsrl_safe() to > safely save these MSRs. > > Reported-and-tested-by: Marcin Kaszewski <marcin.kaszewski@intel.com> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Acked-by: Pavel Machek <pavel@ucw.cz> > Signed-off-by: Chen Yu <yu.c.chen@intel.com> > --- > v7: > - Use the improved version of changelog, and > modify the patch according to: > https://patchwork.kernel.org/patch/7637861/ > --- > arch/x86/include/asm/msr.h | 10 +++++ > arch/x86/include/asm/suspend_32.h | 1 + > arch/x86/include/asm/suspend_64.h | 1 + > arch/x86/power/cpu.c | 94 +++++++++++++++++++++++++++++++++++++++ > 4 files changed, 106 insertions(+)
Ok, this version looks mostly good - I've applied it with some other minor edits to field and variable naming. Please double check the end result that you'll see in the tip-bot notification email once I've pushed it out after some testing.
Thanks,
Ingo
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