Re: [PATCH 3/3] powerpc: Set crashkernel offset to mid of RMA region

[Sourabh Jain]

On 04/10/21 21:36, Aneesh Kumar K.V wrote:
> On 10/4/21 20:41, Sourabh Jain wrote:
> > On large config LPARs (having 192 and more cores), Linux fails to boot
> > due to insufficient memory in the first memory block. It is due to the
> > reserve crashkernel area starts at 128MB offset by default and which
> > doesn't leave enough space in the first memory block to accommodate
> > memory for other essential system resources.
> >
> > Given that the RMA region size can be 512MB or more, setting the
> > crashkernel offset to mid of RMA size will leave enough space to
> > kernel to allocate memory for other system resources in the first
> > memory block.
> >
> > Signed-off-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
> > Reported-and-tested-by: Abdul haleem <abdhalee@xxxxxxxxxxxxxxxxxx>
> > ---
> >   arch/powerpc/kernel/rtas.c |  3 +++
> >   arch/powerpc/kexec/core.c  | 13 +++++++++----
> >   2 files changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> > index ff80bbad22a5..ce5e62bb4d8e 100644
> > --- a/arch/powerpc/kernel/rtas.c
> > +++ b/arch/powerpc/kernel/rtas.c
> > @@ -1235,6 +1235,9 @@ int __init early_init_dt_scan_rtas(unsigned 
> > long node,
> >       entryp = of_get_flat_dt_prop(node, "linux,rtas-entry", NULL);
> >       sizep  = of_get_flat_dt_prop(node, "rtas-size", NULL);
> >   +    if (of_get_flat_dt_prop(node, "ibm,hypertas-functions", NULL))
> > +        powerpc_firmware_features |= FW_FEATURE_LPAR;
> > +
>
> The equivalent check that we currently do more than checking 
> ibm,hypertas-functions.
>
>     if (!strcmp(uname, "rtas") || !strcmp(uname, "rtas@0")) {
>         prop = of_get_flat_dt_prop(node, "ibm,hypertas-functions",
>                        &len);
>         if (prop) {
>             powerpc_firmware_features |= FW_FEATURE_LPAR;
>             fw_hypertas_feature_init(prop, len);
>         }
>
>
> also do we expect other firmware features to be set along with 
> FW_FEATURE_LPAR?

This patch needs to move crash kernel reservation to mid point of rma 
size for LPAR in reserve_crashkernel() function. Since 
reserve_crashkernel() is called too early even before 
powerpc_firmware_features is set with FW_FEATURE_LPAR, the check for if 
(firmware_has_feature(FW_FEATURE_LPAR)) fails and hence we only need to 
make sure that we set this flag early during early_init_dt_scan_rtas().

The rest of the LPAR specific initialization isn't required at this 
point and will be still done during pseries_probe_fw_features() as usual.

Thanks,
Sourabh Jain