From: Sourabh Jain sourabhjain@linux.ibm.com
[ Upstream commit 7c5ed82b800d8615cdda00729e7b62e5899f0b13 ]
On large config LPARs (having 192 and more cores), Linux fails to boot due to insufficient memory in the first memblock. It is due to the memory reservation for the crash kernel which starts at 128MB offset of the first memblock. This memory reservation for the crash kernel doesn't leave enough space in the first memblock to accommodate other essential system resources.
The crash kernel start address was set to 128MB offset by default to ensure that the crash kernel get some memory below the RMA region which is used to be of size 256MB. But given that the RMA region size can be 512MB or more, setting the crash kernel offset to mid of RMA size will leave enough space for the kernel to allocate memory for other system resources.
Since the above crash kernel offset change is only applicable to the LPAR platform, the LPAR feature detection is pushed before the crash kernel reservation. The rest of LPAR specific initialization will still be done during pseries_probe_fw_features as usual.
This patch is dependent on changes to paca allocation for boot CPU. It expect boot CPU to discover 1T segment support which is introduced by the patch posted here: https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-January/239175.html
Reported-by: Abdul haleem abdhalee@linux.vnet.ibm.com Signed-off-by: Sourabh Jain sourabhjain@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20220204085601.107257-1-sourabhjain@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/rtas.c | 6 ++++++ arch/powerpc/kexec/core.c | 15 +++++++++++---- 2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index ff80bbad22a5..e18a725a8e5d 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -1235,6 +1235,12 @@ 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);
+#ifdef CONFIG_PPC64 + /* need this feature to decide the crashkernel offset */ + if (of_get_flat_dt_prop(node, "ibm,hypertas-functions", NULL)) + powerpc_firmware_features |= FW_FEATURE_LPAR; +#endif + 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 a2242017e55f..11b327fa135c 100644 --- a/arch/powerpc/kexec/core.c +++ b/arch/powerpc/kexec/core.c @@ -134,11 +134,18 @@ 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. + * On the LPAR platform place the crash kernel to mid of + * RMA size (512MB or more) to ensure the crash kernel + * gets enough space to place itself and some stack to be + * in the first segment. At the same time normal kernel + * also get enough space to allocate memory for essential + * system resource in the first segment. Keep the crash + * kernel starts at 128MB offset on other platforms. */ - 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