[v1] Remove time reset notifications

[Qemu-devel] [for 4.2 PATCH 0/3] Remove time reset notifications

Dr. David Alan Gilbert (git) posted 3 patches 4 years, 9 months ago

Diff against v2
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Test asan passed

Test FreeBSD passed

Test docker-mingw@fedora passed

Test docker-clang@ubuntu passed

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Test s390x passed

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git fetch https://github.com/patchew-project/qemu tags/patchew/20190722150717.10564-1-dgilbert@redhat.com

Maintainers: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>, "Michael S. Tsirkin" <mst@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

There is a newer version of this series

hw/timer/mc146818rtc.c   | 19 -------------------
include/qemu/timer.h     | 35 ----------------------------------
replay/replay-snapshot.c |  3 +--
util/qemu-timer.c        | 41 +---------------------------------------
4 files changed, 2 insertions(+), 96 deletions(-)

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[Qemu-devel] [for 4.2 PATCH 0/3] Remove time reset notifications

Posted by Dr. David Alan Gilbert (git) 4 years, 9 months ago

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Timers have a mechanism for detecting host clock jumps; this relied
on noticing if the time had gone backwards or if it had gone forward
more than 60s since we last read it.  This had assumed that we regularly
read the time, which isn't true any more - we might not read the host
timer until the guest explicitly reads the guest RTC (e.g. hwclock).
This falsely triggers the reset mechanism.

The reset mechanism was only used by the mc146818 (i.e. PC) RTC
anyway; so lets remove it.

Dr. David Alan Gilbert (3):
  mc146818rtc: Remove reset notifiers
  timer: Remove reset notifiers
  timer: last, remove last bits of last

 hw/timer/mc146818rtc.c   | 19 -------------------
 include/qemu/timer.h     | 35 ----------------------------------
 replay/replay-snapshot.c |  3 +--
 util/qemu-timer.c        | 41 +---------------------------------------
 4 files changed, 2 insertions(+), 96 deletions(-)

-- 
2.21.0

Re: [Qemu-devel] [for 4.2 PATCH 0/3] Remove time reset notifications

Posted by Paolo Bonzini 4 years, 9 months ago

On 22/07/19 17:07, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Timers have a mechanism for detecting host clock jumps; this relied
> on noticing if the time had gone backwards or if it had gone forward
> more than 60s since we last read it.  This had assumed that we regularly
> read the time, which isn't true any more - we might not read the host
> timer until the guest explicitly reads the guest RTC (e.g. hwclock).
> This falsely triggers the reset mechanism.
> 
> The reset mechanism was only used by the mc146818 (i.e. PC) RTC
> anyway; so lets remove it.
> 
> Dr. David Alan Gilbert (3):
>   mc146818rtc: Remove reset notifiers
>   timer: Remove reset notifiers
>   timer: last, remove last bits of last
> 
>  hw/timer/mc146818rtc.c   | 19 -------------------
>  include/qemu/timer.h     | 35 ----------------------------------
>  replay/replay-snapshot.c |  3 +--
>  util/qemu-timer.c        | 41 +---------------------------------------
>  4 files changed, 2 insertions(+), 96 deletions(-)
> 

Queued, thanks.

Paolo