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

Aneesh Kumar K.V
2021-10-04T16:20:56Z

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@linux.ibm.com>
> Reported-and-tested-by: Abdul haleem <abdhalee@linux.vnet.ibm.com>
> ---
> 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?

> if (basep && entryp && sizep) {
> rtas.base = *basep;
> rtas.entry = *entryp;
> diff --git a/arch/powerpc/kexec/core.c b/arch/powerpc/kexec/core.c
> index 48525e8b5730..f69cf3e370ec 100644
> --- a/arch/powerpc/kexec/core.c
> +++ b/arch/powerpc/kexec/core.c
> @@ -147,11 +147,16 @@ void __init reserve_crashkernel(void)
> if (!crashk_res.start) {
> #ifdef CONFIG_PPC64
> /*
> - * On 64bit we split the RMO in half but cap it at half of
> - * a small SLB (128MB) since the crash kernel needs to place
> - * itself and some stacks to be in the first segment.
> + * crash kernel needs to placed in the first segment. On LPAR
> + * setting crash kernel start to mid of RMA size (512MB or more)
> + * would help primary kernel to boot properly on large config
> + * LPAR (with core count 192 or more) and for the reset keep
> + * cap the crash kernel start at 128MB offse.
> */
> - crashk_res.start = min(0x8000000ULL, (ppc64_rma_size / 2));
> + if (firmware_has_feature(FW_FEATURE_LPAR))
> + crashk_res.start = ppc64_rma_size / 2;
> + else
> + crashk_res.start = min(0x8000000ULL, (ppc64_rma_size / 2));
> #else
> crashk_res.start = KDUMP_KERNELBASE;
> #endif
>