powerpc: Fix up the kdump base cap to 128M

The current logic sets the kdump base to min of 2G or ppc64_rma_size/2.
On PowerNV kernel the first memory block 'memory@0' can be very large,
equal to the DIMM size with ppc64_rma_size value capped to 1G. Hence on
PowerNV, kdump base is set to 512M resulting kdump to fail while allocating
paca array. This is because, paca need its memory from RMA region capped
at 256M (see allocate_pacas()).

This patch lowers the kdump base cap to 128M so that kdump kernel can
successfully get memory below 256M for paca allocation.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
index 88a7fb458dfd50f0201d269d8177007cc382c62d..75d4f7340da893bc2825f97dda750409d8963323 100644 (file)
--- a/arch/powerpc/kernel/machine_kexec.c
+++ b/arch/powerpc/kernel/machine_kexec.c
@@ -148,7 +148,7 @@ void __init reserve_crashkernel(void)
                 * a small SLB (128MB) since the crash kernel needs to place
                 * itself and some stacks to be in the first segment.
                 */
-               crashk_res.start = min(0x80000000ULL, (ppc64_rma_size / 2));
+               crashk_res.start = min(0x8000000ULL, (ppc64_rma_size / 2));
 #else
                crashk_res.start = KDUMP_KERNELBASE;
 #endif