RE: [PATCH] [v4] x86, suspend: Save/restore extra MSR registers for suspend

[Chen, Yu C]

Thanks Pavel !

Hi, Ingo,
do you have a bandwidth to help look at this version, 
since this bug has been on bugzilla for a while.
Thanks a lot.

Best Regards,
Yu

> -----Original Message-----
> From: Pavel Machek [mailto:pavel@xxxxxx]
> Sent: Thursday, September 17, 2015 1:30 PM
> To: Chen, Yu C
> Cc: rjw@xxxxxxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx;
> hpa@xxxxxxxxx; bp@xxxxxxxxx; Zhang, Rui; linux-pm@xxxxxxxxxxxxxxx;
> x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] [v4] x86, suspend: Save/restore extra MSR registers for
> suspend
> 
> On Thu 2015-08-27 11:18:27, Chen Yu wrote:
> > A bug is reported(https://bugzilla.redhat.com/show_bug.cgi?id=1227208)
> > that, after resumed from S3, CPU is running at a low speed.
> > After investigation, it is found that, BIOS has modified the value of
> > THERM_CONTROL register during S3, and changes it from 0 to 0x10, since
> > value of 0x10 means CPU can only get 25% of the Duty Cycle, this
> > triggers the problem.
> >
> > Here is a simple scenario to reproduce the issue:
> > 1.Boot up the system
> > 2.Get MSR with address 0x19a, it should be 0 3.Put the system into
> > sleep, then wake it up 4.Get MSR with address 0x19a, it should be
> > 0(actually it shows 0x10)
> >
> > Although this is a BIOS issue, it would be more robust for linux to
> > deal with this situation. This patch fixes this issue by introducing a
> > framework to save/restore specified MSR registers(THERM_CONTROL in
> > this case) for suspend/resume.
> >
> > When user encounters a problematic platform and needs to protect the
> > MSRs during suspending, he can simply add a quirk entry in
> > msr_save_dmi_table, and customizes 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 suspended,
> the
> > MSRs indicated by these IDs will be restored to their original values
> > before suspended.
> >
> > Since both 64/32-bit kernels are affected, this patch covers 64/32-bit
> > common 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.
> >
> > Tested-by: Marcin Kaszewski <marcin.kaszewski@xxxxxxxxx>
> > Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
> 
> Acked-by: Pavel Machek <pavel@xxxxxx>
> 
> --

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