• Chen Yu's avatar
    x86/pm: Introduce quirk framework to save/restore extra MSR registers around suspend/resume · 7a9c2dd0
    Chen Yu authored
    A bug was reported that on certain Broadwell platforms, after
    resuming from S3, the CPU is running at an anomalously low
    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: default avatarMarcin Kaszewski <marcin.kaszewski@intel.com>
    Signed-off-by: default avatarChen Yu <yu.c.chen@intel.com>
    Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Acked-by: default avatarPavel Machek <pavel@ucw.cz>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: bp@suse.de
    Cc: len.brown@intel.com
    Cc: linux@horizon.com
    Cc: luto@kernel.org
    Cc: rjw@rjwysocki.net
    Link: http://lkml.kernel.org/r/c9abdcbc173dd2f57e8990e304376f19287e92ba.1448382971.git.yu.c.chen@intel.com
    [ More edits to the naming of data structures. ]
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
cpu.c 10.8 KB