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x86/tsc: Remove the TSC_ADJUST clamp 

Now that all affected platforms have a microcode update; and we check
this and disable TSC_DEADLINE and print a microcode revision update
error if its too old, we can remove the TSC_ADJUST clamp.

This should help with systems where the second socket runs ahead of
the first socket and needs a negative adjustment. In this case we'd
hit the 0 clamp and give up for not achieving synchronization.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: kevin.b.stanton@intel.com
Link: http://lkml.kernel.org/r/20170531155306.100950003@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Peter Zijlstra 2017-05-31 17:52:04 +02:00 committed by Thomas Gleixner
parent bd9240a18e
commit 855615eee9
1 changed files with 1 additions and 20 deletions
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21
arch/x86/kernel/tsc_sync.c
View File

@ -71,13 +71,8 @@ static void tsc_sanitize_first_cpu(struct tsc_adjust *cur, s64 bootval,
* non zero. We don't do that on non boot cpus because physical
* hotplug should have set the ADJUST register to a value > 0 so
* the TSC is in sync with the already running cpus.
*
* But we always force positive ADJUST values. Otherwise the TSC
* deadline timer creates an interrupt storm. We also have to
* prevent values > 0x7FFFFFFF as those wreckage the timer as well.
*/
if ((bootcpu && bootval != 0) || (!bootcpu && bootval < 0) ||
(bootval > 0x7FFFFFFF)) {
if (bootcpu && bootval != 0) {
pr_warn(FW_BUG "TSC ADJUST: CPU%u: %lld force to 0\n", cpu,
bootval);
wrmsrl(MSR_IA32_TSC_ADJUST, 0);
@ -451,20 +446,6 @@ retry:
*/
cur->adjusted += cur_max_warp;
/*
* TSC deadline timer stops working or creates an interrupt storm
* with adjust values < 0 and > x07ffffff.
*
* To allow adjust values > 0x7FFFFFFF we need to disable the
* deadline timer and use the local APIC timer, but that requires
* more intrusive changes and we do not have any useful information
* from Intel about the underlying HW wreckage yet.
*/
if (cur->adjusted < 0)
cur->adjusted = 0;
if (cur->adjusted > 0x7FFFFFFF)
cur->adjusted = 0x7FFFFFFF;
pr_warn("TSC ADJUST compensate: CPU%u observed %lld warp. Adjust: %lld\n",
cpu, cur_max_warp, cur->adjusted);