[PATCH 2/2] powerpc/kexec: avoid hard coding when automatically allocating mem for crashkernel

[Christophe Leroy]

Le 31/08/2018 à 09:30, Pingfan Liu a écrit :
> If no start address is specified for crashkernel, the current program hard
> code as: crashk_res.start = min(0x8000000ULL, (ppc64_rma_size / 2));
> This limits the candidate memory region, and may cause failure while there
> is enough mem for crashkernel. This patch suggests to find a suitable mem
> chunk by memblock_find_in_range()

Seems like something more or less similar was done with commit 
7c5ed82b800d ("powerpc: Set crashkernel offset to mid of RMA region")

At least your patch conflicts with that commit, so if you think your 
patch is still relevant, please rebase and resubmit your series.

Thanks
Christophe

> 
> Signed-off-by: Pingfan Liu <kernelfans at gmail.com>
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Hari Bathini <hbathini at linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> Cc: Anton Blanchard <anton at samba.org>
> ---
>   arch/powerpc/kernel/machine_kexec.c | 24 +++++++++++++++---------
>   arch/powerpc/kernel/prom.c          |  7 +++++--
>   2 files changed, 20 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index 63f5a93..78005bf 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -22,6 +22,9 @@
>   #include <asm/pgalloc.h>
>   #include <asm/prom.h>
>   #include <asm/sections.h>
> +#include <asm/mmu.h>
> +
> +#include "setup.h"
>   
>   void machine_kexec_mask_interrupts(void) {
>   	unsigned int i;
> @@ -117,6 +120,7 @@ void machine_kexec(struct kimage *image)
>   void __init reserve_crashkernel(void)
>   {
>   	unsigned long long crash_size, crash_base;
> +	phys_addr_t start, up_boundary;
>   	int ret;
>   
>   	/* use common parsing */
> @@ -146,22 +150,24 @@ void __init reserve_crashkernel(void)
>   #else
>   	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.
> -		 */
> -		crashk_res.start = min(0x8000000ULL, (ppc64_rma_size / 2));
> +		up_boundary = min(ppc64_bolted_size(), ppc64_rma_size);
> +		start = memblock_find_in_range(KDUMP_KERNELBASE, up_boundary,
> +				crash_size, PAGE_SIZE);
> +		if (start == 0) {
> +			pr_err("Failed to reserve memory for crashkernel!\n");
> +			crashk_res.start = crashk_res.end = 0;
> +			return;
> +		} else
> +			crashk_res.start = start;
>   #else
>   		crashk_res.start = KDUMP_KERNELBASE;
>   #endif
>   	}
>   
> -	crash_base = PAGE_ALIGN(crashk_res.start);
> -	if (crash_base != crashk_res.start) {
> +	if (crashk_res.start != PAGE_ALIGN(crashk_res.start)) {
>   		printk("Crash kernel base must be aligned to 0x%lx\n",
>   				PAGE_SIZE);
> -		crashk_res.start = crash_base;
> +		crashk_res.start = PAGE_ALIGN(crashk_res.start);
>   	}
>   
>   #endif
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index cae4a78..8b2ab99 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -688,6 +688,7 @@ static void tm_init(void) { }
>   void __init early_init_devtree(void *params)
>   {
>   	phys_addr_t limit;
> +	bool fadump_enabled = false;
>   
>   	DBG(" -> early_init_devtree(%p)\n", params);
>   
> @@ -737,9 +738,9 @@ void __init early_init_devtree(void *params)
>   	 * If we fail to reserve memory for firmware-assisted dump then
>   	 * fallback to kexec based kdump.
>   	 */
> -	if (fadump_reserve_mem() == 0)
> +	if (fadump_reserve_mem() == 1)
> +		fadump_enabled = true;
>   #endif
> -		reserve_crashkernel();
>   	early_reserve_mem();
>   
>   	/* Ensure that total memory size is page-aligned. */
> @@ -761,6 +762,8 @@ void __init early_init_devtree(void *params)
>   
>   	dt_cpu_ftrs_scan();
>   	mmu_early_init_devtree();
> +	if (!fadump_enabled)
> +		reserve_crashkernel();
>   
>   	/* Retrieve CPU related informations from the flat tree
>   	 * (altivec support, boot CPU ID, ...)