[SRU J][PATCH 2/2] UBUNTU: [Config] CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE

[Stefan Bader]

On 02.10.23 18:54, Michael Reed wrote:
> Hi Stefan,
> 
> Would you also recommend that I disable this for arm64?

Sorry this has been neglected a bit. We did discuss this again recently 
and generally the reaction is more hesitant. First, as mentioned before, 
this is an option which changes behavior in general. And none of us 
knows what the exact effect is for x86. Could this result in a server 
coming up with less memory than expected (than it was before)?
Is it really absolutely necessary to change general behavior to fix a 
single driver? And if it is necessary, then this should be changed in 
all kernels following (Lunar, Mantic, ...).

-Stefan

> 
> -Michael
> 
> 
> On Thu, Sep 28, 2023 at 11:03 AM Stefan Bader 
> <stefan.bader at canonical.com <mailto:stefan.bader at canonical.com>> wrote:
> 
>     On 22.09.23 19:09, Michael Reed wrote:
>      > From: Michael Reed <Michael.Reed at canonical.com
>     <mailto:Michael.Reed at canonical.com>>
>      >
>      > BugLink: https://bugs.launchpad.net/bugs/2028158
>     <https://bugs.launchpad.net/bugs/2028158>
>      > By default this is enabled, but it is causing an issue
>     reconfiguring device dax memory, thus
>      > it is being disabled.
>      >
>      > Signed-off-by: Michael Reed <Michael.Reed at canonical.com
>     <mailto:Michael.Reed at canonical.com>>
>      > ---
>      >   debian.master/config/annotations | 2 +-
>      >   1 file changed, 1 insertion(+), 1 deletion(-)
>      >
>      > diff --git a/debian.master/config/annotations
>     b/debian.master/config/annotations
>      > index 5f854837a810..b9081681267c 100644
>      > --- a/debian.master/config/annotations
>      > +++ b/debian.master/config/annotations
>      > @@ -348,7 +348,7 @@ CONFIG_LOAD_PPC_KEYS                         
>        note<'LP:1866909'>
>      >   CONFIG_LOCALVERSION_AUTO                       
>     policy<{'amd64': 'n', 'arm64': 'n', 'armhf': 'n', 'ppc64el': 'n',
>     's390x': 'n'}>
>      >   CONFIG_LOCALVERSION_AUTO                        note<'triggers
>     packaging failures'>
>      >
>      > -CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE            policy<{'amd64':
>     'y', 'arm64': 'y', 'ppc64el': 'n', 's390x': 'n'}>
>      > +CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE            policy<{'amd64':
>     'n', 'arm64': 'y', 'ppc64el': 'n', 's390x': 'n'}>
>      >   CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE           
>     note<'LP:1709171 LP:1848492'>
>      >
>      >   CONFIG_MFD_SM501                               
>     policy<{'amd64': 'm', 'arm64': 'm', 'armhf': 'y', 'ppc64el': 'm',
>     's390x': 'n'}>
> 
>     That would be a more fundamental behavior change which at least should
>     be added as a reference to the annotation below. Seems for ppc64el and
>     s390x this was changed in the past but I am not sure whether this might
>     break assumptions or use cases on the x86 side.
>     Adding a few more cc's for discussion/awareness.
> 
>     -- 
>     - Stefan
> 
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