whiterose

linux unikernel
Log | Files | Refs | README | LICENSE | git clone https://git.ne02ptzero.me/git/whiterose

commit 351e1aa6cb4b136e3f772605071d7a8db3c5b4e0
parent f907bb4c326d145c13504db184f38557d169f4bc
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 27 Jan 2019 11:57:46 -0800

Merge branch 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 timer fixes from Thomas Gleixner:
 "Two commits which were missed to be sent during the merge window.

   - The TSC calibration fix turns out to be more urgent as recent
     Skylake-X systems seem to have massive trouble with calibration
     disturbance. This should go back into stable for that reason and it
     the risk of breakage is rather low.

   - Drop an unused define"

* 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/hpet: Remove unused FSEC_PER_NSEC define
  x86/tsc: Make calibration refinement more robust

Diffstat:
March/x86/kernel/hpet.c | 4----
March/x86/kernel/tsc.c | 30++++++++++++++++--------------
2 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c @@ -21,10 +21,6 @@ #define HPET_MASK CLOCKSOURCE_MASK(32) -/* FSEC = 10^-15 - NSEC = 10^-9 */ -#define FSEC_PER_NSEC 1000000L - #define HPET_DEV_USED_BIT 2 #define HPET_DEV_USED (1 << HPET_DEV_USED_BIT) #define HPET_DEV_VALID 0x8 diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c @@ -297,15 +297,16 @@ static int __init tsc_setup(char *str) __setup("tsc=", tsc_setup); -#define MAX_RETRIES 5 -#define SMI_TRESHOLD 50000 +#define MAX_RETRIES 5 +#define TSC_DEFAULT_THRESHOLD 0x20000 /* - * Read TSC and the reference counters. Take care of SMI disturbance + * Read TSC and the reference counters. Take care of any disturbances */ static u64 tsc_read_refs(u64 *p, int hpet) { u64 t1, t2; + u64 thresh = tsc_khz ? tsc_khz >> 5 : TSC_DEFAULT_THRESHOLD; int i; for (i = 0; i < MAX_RETRIES; i++) { @@ -315,7 +316,7 @@ static u64 tsc_read_refs(u64 *p, int hpet) else *p = acpi_pm_read_early(); t2 = get_cycles(); - if ((t2 - t1) < SMI_TRESHOLD) + if ((t2 - t1) < thresh) return t2; } return ULLONG_MAX; @@ -703,15 +704,15 @@ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) * zero. In each wait loop iteration we read the TSC and check * the delta to the previous read. We keep track of the min * and max values of that delta. The delta is mostly defined - * by the IO time of the PIT access, so we can detect when a - * SMI/SMM disturbance happened between the two reads. If the + * by the IO time of the PIT access, so we can detect when + * any disturbance happened between the two reads. If the * maximum time is significantly larger than the minimum time, * then we discard the result and have another try. * * 2) Reference counter. If available we use the HPET or the * PMTIMER as a reference to check the sanity of that value. * We use separate TSC readouts and check inside of the - * reference read for a SMI/SMM disturbance. We dicard + * reference read for any possible disturbance. We dicard * disturbed values here as well. We do that around the PIT * calibration delay loop as we have to wait for a certain * amount of time anyway. @@ -744,7 +745,7 @@ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) if (ref1 == ref2) continue; - /* Check, whether the sampling was disturbed by an SMI */ + /* Check, whether the sampling was disturbed */ if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) continue; @@ -1268,7 +1269,7 @@ static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work); */ static void tsc_refine_calibration_work(struct work_struct *work) { - static u64 tsc_start = -1, ref_start; + static u64 tsc_start = ULLONG_MAX, ref_start; static int hpet; u64 tsc_stop, ref_stop, delta; unsigned long freq; @@ -1283,14 +1284,15 @@ static void tsc_refine_calibration_work(struct work_struct *work) * delayed the first time we expire. So set the workqueue * again once we know timers are working. */ - if (tsc_start == -1) { + if (tsc_start == ULLONG_MAX) { +restart: /* * Only set hpet once, to avoid mixing hardware * if the hpet becomes enabled later. */ hpet = is_hpet_enabled(); - schedule_delayed_work(&tsc_irqwork, HZ); tsc_start = tsc_read_refs(&ref_start, hpet); + schedule_delayed_work(&tsc_irqwork, HZ); return; } @@ -1300,9 +1302,9 @@ static void tsc_refine_calibration_work(struct work_struct *work) if (ref_start == ref_stop) goto out; - /* Check, whether the sampling was disturbed by an SMI */ - if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX) - goto out; + /* Check, whether the sampling was disturbed */ + if (tsc_stop == ULLONG_MAX) + goto restart; delta = tsc_stop - tsc_start; delta *= 1000000LL;