[PATCH v3 1/2] public/hvm/params.h: fix comment for timer_mode default

[PATCH v3 1/2] public/hvm/params.h: fix comment for timer_mode default

[Doug Goldstein]

In libxl__domain_build_info_setdefault() in
tools/libxl/libxl_create.c the default for timer_mode for HVM
and PVH is LIBXL_TIMER_MODE_NO_DELAY_FOR_MISSED_TICKS so adjust the
comments in the header to reflect this.
---
CC: Wei Liu <wei.liu2@citrix.com>
CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: George Dunlap <george.dunlap@eu.citrix.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Tim Deegan <tim@xen.org>

change from v2:
- Roger noted that the code differed from the
  header that I used as the source of truth
  so that has created this patch
---
 xen/include/public/hvm/params.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index 2ec2e7c80f..ce6748e4a8 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -152,12 +152,12 @@
 
 /*
  * Set mode for virtual timers (currently x86 only):
- *  delay_for_missed_ticks (default):
+ *  delay_for_missed_ticks:
  *   Do not advance a vcpu's time beyond the correct delivery time for
  *   interrupts that have been missed due to preemption. Deliver missed
  *   interrupts when the vcpu is rescheduled and advance the vcpu's virtual
  *   time stepwise for each one.
- *  no_delay_for_missed_ticks:
+ *  no_delay_for_missed_ticks (default):
  *   As above, missed interrupts are delivered, but guest time always tracks
  *   wallclock (i.e., real) time while doing so.
  *  no_missed_ticks_pending:
-- 
2.13.6


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[PATCH v3 2/2] docs: note default for timer_mode in xl.cfg man

[Doug Goldstein]

There was no default documented but inspecting
libxl__domain_build_info_setdefault() shows the default to be
LIBXL_TIMER_MODE_NO_DELAY_FOR_MISSED_TICKS.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
---
CC: Wei Liu <wei.liu2@citrix.com>
CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
# George for the 4.8 and 4.9 backport
CC: George Dunlap <george.dunlap@eu.citrix.com>

change from v2:
- Roger noted that the code differed from the
  header that I used as the source of truth
change from v1:
- added same docs addition to HVM
---
 docs/man/xl.cfg.pod.5.in | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
index b7b91d8627..6b3ee81602 100644
--- a/docs/man/xl.cfg.pod.5.in
+++ b/docs/man/xl.cfg.pod.5.in
@@ -1889,7 +1889,7 @@ advance the vCPU's virtual time stepwise for each one.
 
 No delay for missed ticks. As above, missed interrupts are delivered,
 but guest time always tracks wallclock (i.e., real) time while doing
-so.
+so. This is the default.
 
 =item B<no_missed_ticks_pending>
 
@@ -2348,13 +2348,14 @@ Specifies the mode for Virtual Timers. The valid values are as follows:
 Delay for missed ticks. Do not advance a vCPU's time beyond the
 correct delivery time for interrupts that have been missed due to
 preemption. Deliver missed interrupts when the vCPU is rescheduled and
-advance the vCPU's virtual time stepwise for each one.
+advance the vCPU's virtual time stepwise for each one. This is the
+default.
 
 =item B<no_delay_for_missed_ticks>
 
 No delay for missed ticks. As above, missed interrupts are delivered,
 but guest time always tracks wallclock (i.e., real) time while doing
-so.
+so. This is the default.
 
 =item B<no_missed_ticks_pending>
 
-- 
2.13.6


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Re: [PATCH v3 2/2] docs: note default for timer_mode in xl.cfg man

[Roger Pau Monné]

On Mon, Jan 15, 2018 at 09:24:52PM -0600, Doug Goldstein wrote:
> There was no default documented but inspecting
> libxl__domain_build_info_setdefault() shows the default to be
> LIBXL_TIMER_MODE_NO_DELAY_FOR_MISSED_TICKS.
> 
> Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
> ---
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Ian Jackson <ian.jackson@eu.citrix.com>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> # George for the 4.8 and 4.9 backport
> CC: George Dunlap <george.dunlap@eu.citrix.com>
> 
> change from v2:
> - Roger noted that the code differed from the
>   header that I used as the source of truth
> change from v1:
> - added same docs addition to HVM
> ---
>  docs/man/xl.cfg.pod.5.in | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
> index b7b91d8627..6b3ee81602 100644
> --- a/docs/man/xl.cfg.pod.5.in
> +++ b/docs/man/xl.cfg.pod.5.in
> @@ -1889,7 +1889,7 @@ advance the vCPU's virtual time stepwise for each one.
>  
>  No delay for missed ticks. As above, missed interrupts are delivered,
>  but guest time always tracks wallclock (i.e., real) time while doing
> -so.
> +so. This is the default.
>  
>  =item B<no_missed_ticks_pending>
>  
> @@ -2348,13 +2348,14 @@ Specifies the mode for Virtual Timers. The valid values are as follows:
>  Delay for missed ticks. Do not advance a vCPU's time beyond the
>  correct delivery time for interrupts that have been missed due to
>  preemption. Deliver missed interrupts when the vCPU is rescheduled and
> -advance the vCPU's virtual time stepwise for each one.
> +advance the vCPU's virtual time stepwise for each one. This is the
> +default.

The chunk above is now stale, since we agreed that
no_delay_for_missed_ticks was the default.

Thanks, Roger.

>  =item B<no_delay_for_missed_ticks>
>  
>  No delay for missed ticks. As above, missed interrupts are delivered,
>  but guest time always tracks wallclock (i.e., real) time while doing
> -so.
> +so. This is the default.
>  
>  =item B<no_missed_ticks_pending>
>  
> -- 
> 2.13.6
> 

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Re: [PATCH v3 1/2] public/hvm/params.h: fix comment for timer_mode default

[Roger Pau Monné]

On Mon, Jan 15, 2018 at 09:24:51PM -0600, Doug Goldstein wrote:
> In libxl__domain_build_info_setdefault() in
> tools/libxl/libxl_create.c the default for timer_mode for HVM
> and PVH is LIBXL_TIMER_MODE_NO_DELAY_FOR_MISSED_TICKS so adjust the
> comments in the header to reflect this.

IMHO this is not correct. The default in the hypervisor when creating
a guest is HVMPTM_delay_for_missed_ticks, so the header is correct.

The default set by libxl is different, but that's something specific
to libxl, and should only be documented in xl.cfg.

This is not very convenient, but sadly in this case the default in the
hypervisor differs from the default set by libxl, which is confusing.

Thanks, Roger.

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