On Sun 2015-08-23 08:20:33, Ingo Molnar wrote: > > * Pavel Machek <pa...@ucw.cz> wrote: > > > On Fri 2015-08-21 19:53:34, Chen Yu wrote: > > > A bug is reported(https://bugzilla.redhat.com/show_bug.cgi?id=1227208) > > > that, after resuming from S3, CPU is working at a low speed. > > > After investigation, it is found that, BIOS has modified the value > > > of THERM_CONTROL register during S3, changes it from 0 to 0x10, > > > while the latter means CPU can only get 25% of the Duty Cycle, > > > and this caused the problem. > > > > > > Simple scenario to reproduce: > > > 1.Boot up system > > > 2.Get MSR with address 0x19a, it should output 0 > > > 3.Put system into sleep, then wake up > > > 4.Get MSR with address 0x19a, it should output 0(actual it outputs 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 > > > for saving/restoring specify MSR registers(THERM_CONTROL in this case) > > > on suspend/resume. > > > > > > When user finds a problematic platform that requires save/restore MSRs, > > > he can simply add quirk in msr_save_dmi_table, and customizes MSR > > > registers in quirk callback, for example: > > > > > > unsigned int msr_id_need_to_save[] = {MSR_ID0, MSR_ID1, MSR_ID2...}; > > > > > > and system ensures that, once resumed from suspend, these MSR indicated > > > by IDs will be restored to their original values before suspend. > > > > > > Since both 64/32-bit kernels are affected, this patch covers 64/32-bit > > > common code path. And because the MSR ids specified by user might not be > > > available or readable in any situation, we use rdmsrl_safe to safely > > > save these MSR registers. > > > > > > Tested-by: Marcin Kaszewski <marcin.kaszew...@intel.com> > > > Signed-off-by: Chen Yu <yu.c.c...@intel.com> > > > > Acked-by: Pavel Machek <pa...@ucw.cz> > > So I like the general structure of the patch and I like the MSR saving > mechanism > it introduces, but it is full of typos and small stylistic uncleanlinesses > which > need to be fixed before this patch can be applied. Please don't ack > incomplete > patches.
Plus, I acked V2 when V3 was available. I was under impression it was a regression, so "slightly urgent", but it looks that was wrong impression, too. Sorry, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/