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  1. 17 Feb, 2020 1 commit
  3. 22 Jun, 2019 1 commit
    • Vincenzo Frascino's avatar
      x86/vdso: Switch to generic vDSO implementation · 7ac87074
      Vincenzo Frascino authored 
      
The x86 vDSO library requires some adaptations to take advantage of the
newly introduced generic vDSO library.

Introduce the following changes:
 - Modification of vdso.c to be compliant with the common vdso datapage
 - Use of lib/vdso for gettimeofday

[ tglx: Massaged changelog and cleaned up the function signature formatting ]
Signed-off-by: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Huw Davies <huw@codeweavers.com>
Cc: Shijith Thotton <sthotton@marvell.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-23-vincenzo.frascino@arm.com
      7ac87074
  5. 24 May, 2019 1 commit
  7. 31 Oct, 2018 1 commit
  9. 19 May, 2018 1 commit
  11. 08 Nov, 2017 1 commit
  13. 02 Mar, 2017 1 commit
  15. 25 Dec, 2016 1 commit
  17. 20 Sep, 2016 1 commit
    • Paolo Bonzini's avatar
      KVM: x86: introduce get_kvmclock_ns · 108b249c
      Paolo Bonzini authored 
      
Introduce a function that reads the exact nanoseconds value that is
provided to the guest in kvmclock.  This crystallizes the notion of
kvmclock as a thin veneer over a stable TSC, that the guest will
(hopefully) convert with NTP.  In other words, kvmclock is *not* a
paravirtualized host-to-guest NTP.

Drop the get_kernel_ns() function, that was used both to get the base
value of the master clock and to get the current value of kvmclock.
The former use is replaced by ktime_get_boot_ns(), the latter is
the purpose of get_kernel_ns().

This also allows KVM to provide a Hyper-V time reference counter that
is synchronized with the time that is computed from the TSC page.
Reviewed-by: default avatarRoman Kagan <rkagan@virtuozzo.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      108b249c
  19. 04 Aug, 2016 1 commit
    • Paolo Bonzini's avatar
      pvclock: introduce seqcount-like API · 3aed64f6
      Paolo Bonzini authored 
      
The version field in struct pvclock_vcpu_time_info basically implements
a seqcount.  Wrap it with the usual read_begin and read_retry functions,
and use these APIs instead of peppering the code with smp_rmb()s.
While at it, change it to the more pedantically correct virt_rmb().

With this change, __pvclock_read_cycles can be simplified noticeably.
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      3aed64f6
  21. 27 Jun, 2016 2 commits
  23. 11 Dec, 2015 1 commit
  25. 27 Apr, 2015 1 commit
  27. 23 Mar, 2015 1 commit
  29. 06 Nov, 2013 2 commits
  31. 18 Jul, 2013 1 commit
  33. 28 Feb, 2013 1 commit
  35. 28 Nov, 2012 5 commits
  37. 28 Nov, 2010 1 commit
  39. 10 Nov, 2010 1 commit
  41. 24 Oct, 2010 1 commit
  43. 19 May, 2010 3 commits
    • Glauber Costa's avatar
      x86, paravirt: don't compute pvclock adjustments if we trust the tsc · 3a0d7256
      Glauber Costa authored 
      
If the HV told us we can fully trust the TSC, skip any
correction
Signed-off-by: default avatarGlauber Costa <glommer@redhat.com>
Acked-by: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
      3a0d7256
    • Glauber Costa's avatar
      x86, paravirt: Add a global synchronization point for pvclock · 489fb490
      Glauber Costa authored 
      
In recent stress tests, it was found that pvclock-based systems
could seriously warp in smp systems. Using ingo's time-warp-test.c,
I could trigger a scenario as bad as 1.5mi warps a minute in some systems.
(to be fair, it wasn't that bad in most of them). Investigating further, I
found out that such warps were caused by the very offset-based calculation
pvclock is based on.

This happens even on some machines that report constant_tsc in its tsc flags,
specially on multi-socket ones.

Two reads of the same kernel timestamp at approx the same time, will likely
have tsc timestamped in different occasions too. This means the delta we
calculate is unpredictable at best, and can probably be smaller in a cpu
that is legitimately reading clock in a forward ocasion.

Some adjustments on the host could make this window less likely to happen,
but still, it pretty much poses as an intrinsic problem of the mechanism.

A while ago, I though about using a shared variable anyway, to hold clock
last state, but gave up due to the high contention locking was likely
to introduce, possibly rendering the thing useless on big machines. I argue,
however, that locking is not necessary.

We do a read-and-return sequence in pvclock, and between read and return,
the global value can have changed. However, it can only have changed
by means of an addition of a positive value. So if we detected that our
clock timestamp is less than the current global, we know that we need to
return a higher one, even though it is not exactly the one we compared to.

OTOH, if we detect we're greater than the current time source, we atomically
replace the value with our new readings. This do causes contention on big
boxes (but big here means *BIG*), but it seems like a good trade off, since
it provide us with a time source guaranteed to be stable wrt time warps.

After this patch is applied, I don't see a single warp in time during 5 days
of execution, in any of the machines I saw them before.
Signed-off-by: default avatarGlauber Costa <glommer@redhat.com>
Acked-by: default avatarZachary Amsden <zamsden@redhat.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Avi Kivity <avi@redhat.com>
CC: Marcelo Tosatti <mtosatti@redhat.com>
CC: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
      489fb490
    • Glauber Costa's avatar
      x86, paravirt: Enable pvclock flags in vcpu_time_info structure · 424c32f1
      Glauber Costa authored 
      
This patch removes one padding byte and transform it into a flags
field. New versions of guests using pvclock will query these flags
upon each read.

Flags, however, will only be interpreted when the guest decides to.
It uses the pvclock_valid_flags function to signal that a specific
set of flags should be taken into consideration. Which flags are valid
are usually devised via HV negotiation.
Signed-off-by: default avatarGlauber Costa <glommer@redhat.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
Acked-by: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
      424c32f1
  45. 14 Jul, 2009 1 commit
  47. 15 Oct, 2008 2 commits
  49. 24 Jun, 2008 1 commit