[PATCH 0/5] xen: cleanup detection of non-essential pv devices

[PATCH 0/5] xen: cleanup detection of non-essential pv devices

[Juergen Gross]

Today the non-essential pv devices are hard coded in the xenbus driver
and this list is lacking multiple entries.

This series reworks the detection logic of non-essential devices by
adding a flag for that purpose to struct xenbus_driver.

Juergen Gross (5):
  xen: add "not_essential" flag to struct xenbus_driver
  xen: flag xen_drm_front to be not essential for system boot
  xen: flag hvc_xen to be not essential for system boot
  xen: flag pvcalls-front to be not essential for system boot
  xen: flag xen_snd_front to be not essential for system boot

 drivers/gpu/drm/xen/xen_drm_front.c        |  1 +
 drivers/input/misc/xen-kbdfront.c          |  1 +
 drivers/tty/hvc/hvc_xen.c                  |  1 +
 drivers/video/fbdev/xen-fbfront.c          |  1 +
 drivers/xen/pvcalls-front.c                |  1 +
 drivers/xen/xenbus/xenbus_probe_frontend.c | 14 +++-----------
 include/xen/xenbus.h                       |  1 +
 sound/xen/xen_snd_front.c                  |  1 +
 8 files changed, 10 insertions(+), 11 deletions(-)

-- 
2.26.2

[PATCH 3/5] xen: flag hvc_xen to be not essential for system boot

[Juergen Gross]

The Xen pv console driver is not essential for boot. Set the respective
flag.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/tty/hvc/hvc_xen.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index f0bf01ea069a..71e0dd2c0ce5 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -522,6 +522,7 @@ static struct xenbus_driver xencons_driver = {
 	.remove = xencons_remove,
 	.resume = xencons_resume,
 	.otherend_changed = xencons_backend_changed,
+	.not_essential = true,
 };
 #endif /* CONFIG_HVC_XEN_FRONTEND */
 
-- 
2.26.2

Re: [PATCH 0/5] xen: cleanup detection of non-essential pv devices

[Jan Beulich]

On 22.10.2021 08:47, Juergen Gross wrote:
> Today the non-essential pv devices are hard coded in the xenbus driver
> and this list is lacking multiple entries.
> 
> This series reworks the detection logic of non-essential devices by
> adding a flag for that purpose to struct xenbus_driver.

I'm wondering whether it wouldn't better be the other way around: The
(hopefully few) essential ones get flagged, thus also making it more
prominent during patch review that a flag gets added (and justification
provided), instead of having to spot the lack of a flag getting set.

Jan

Re: [PATCH 0/5] xen: cleanup detection of non-essential pv devices

[Juergen Gross]

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On 22.10.21 09:24, Jan Beulich wrote:
> On 22.10.2021 08:47, Juergen Gross wrote:
>> Today the non-essential pv devices are hard coded in the xenbus driver
>> and this list is lacking multiple entries.
>>
>> This series reworks the detection logic of non-essential devices by
>> adding a flag for that purpose to struct xenbus_driver.
> 
> I'm wondering whether it wouldn't better be the other way around: The
> (hopefully few) essential ones get flagged, thus also making it more
> prominent during patch review that a flag gets added (and justification
> provided), instead of having to spot the lack of a flag getting set.

Not flagging a non-essential one is less problematic than not flagging
an essential driver IMO.

For some drivers I'm on the edge, BTW. The pv 9pfs driver ought to be
non-essential in most cases, but there might be use cases where it is
needed, so I didn't set its non_essential flag.

Same applies to pv-usb and maybe pv-scsi, while pv-tpm probably really
is essential.

With the current series I'm ending up with 6 non-essential drivers and
6 essential ones, so either way needs the same number of drivers
modified.


Juergen

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Re: [PATCH 0/5] xen: cleanup detection of non-essential pv devices

[Juergen Gross]

[-- Attachment #1.1.1: Type: text/plain, Size: 1194 bytes --]

On 22.10.21 08:47, Juergen Gross wrote:
> Today the non-essential pv devices are hard coded in the xenbus driver
> and this list is lacking multiple entries.
> 
> This series reworks the detection logic of non-essential devices by
> adding a flag for that purpose to struct xenbus_driver.
> 
> Juergen Gross (5):
>    xen: add "not_essential" flag to struct xenbus_driver
>    xen: flag xen_drm_front to be not essential for system boot
>    xen: flag hvc_xen to be not essential for system boot
>    xen: flag pvcalls-front to be not essential for system boot
>    xen: flag xen_snd_front to be not essential for system boot
> 
>   drivers/gpu/drm/xen/xen_drm_front.c        |  1 +
>   drivers/input/misc/xen-kbdfront.c          |  1 +
>   drivers/tty/hvc/hvc_xen.c                  |  1 +
>   drivers/video/fbdev/xen-fbfront.c          |  1 +
>   drivers/xen/pvcalls-front.c                |  1 +
>   drivers/xen/xenbus/xenbus_probe_frontend.c | 14 +++-----------
>   include/xen/xenbus.h                       |  1 +
>   sound/xen/xen_snd_front.c                  |  1 +
>   8 files changed, 10 insertions(+), 11 deletions(-)
> 

Any further comments?


Juergen

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Re: [PATCH 0/5] xen: cleanup detection of non-essential pv devices

[Boris Ostrovsky]

On 11/22/21 3:20 AM, Juergen Gross wrote:
> On 22.10.21 08:47, Juergen Gross wrote:
>> Today the non-essential pv devices are hard coded in the xenbus driver
>> and this list is lacking multiple entries.
>>
>> This series reworks the detection logic of non-essential devices by
>> adding a flag for that purpose to struct xenbus_driver.
>>
>> Juergen Gross (5):
>>    xen: add "not_essential" flag to struct xenbus_driver
>>    xen: flag xen_drm_front to be not essential for system boot
>>    xen: flag hvc_xen to be not essential for system boot
>>    xen: flag pvcalls-front to be not essential for system boot
>>    xen: flag xen_snd_front to be not essential for system boot
>>
>>   drivers/gpu/drm/xen/xen_drm_front.c        |  1 +
>>   drivers/input/misc/xen-kbdfront.c          |  1 +
>>   drivers/tty/hvc/hvc_xen.c                  |  1 +
>>   drivers/video/fbdev/xen-fbfront.c          |  1 +
>>   drivers/xen/pvcalls-front.c                |  1 +
>>   drivers/xen/xenbus/xenbus_probe_frontend.c | 14 +++-----------
>>   include/xen/xenbus.h                       |  1 +
>>   sound/xen/xen_snd_front.c                  |  1 +
>>   8 files changed, 10 insertions(+), 11 deletions(-)
>>
>
> Any further comments?
>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>


(I'll fix the semicolon typo in the last patch, no need to resend)

Re: [PATCH 0/5] xen: cleanup detection of non-essential pv devices

[Boris Ostrovsky]

On 11/22/21 3:20 AM, Juergen Gross wrote:
> On 22.10.21 08:47, Juergen Gross wrote:
>> Today the non-essential pv devices are hard coded in the xenbus driver
>> and this list is lacking multiple entries.
>>
>> This series reworks the detection logic of non-essential devices by
>> adding a flag for that purpose to struct xenbus_driver.
>>
>> Juergen Gross (5):
>>    xen: add "not_essential" flag to struct xenbus_driver
>>    xen: flag xen_drm_front to be not essential for system boot
>>    xen: flag hvc_xen to be not essential for system boot
>>    xen: flag pvcalls-front to be not essential for system boot
>>    xen: flag xen_snd_front to be not essential for system boot
>>
>>   drivers/gpu/drm/xen/xen_drm_front.c        |  1 +
>>   drivers/input/misc/xen-kbdfront.c          |  1 +
>>   drivers/tty/hvc/hvc_xen.c                  |  1 +
>>   drivers/video/fbdev/xen-fbfront.c          |  1 +
>>   drivers/xen/pvcalls-front.c                |  1 +
>>   drivers/xen/xenbus/xenbus_probe_frontend.c | 14 +++-----------
>>   include/xen/xenbus.h                       |  1 +
>>   sound/xen/xen_snd_front.c                  |  1 +
>>   8 files changed, 10 insertions(+), 11 deletions(-)
>>
>



Applied to for-linus-5.16c


-boris