Subject: Re: [PATCH 2/2] powerpc/fadump: avoid holes in boot memory area when fadump is registered

From: Pingfan Liu <[email-masked]>
Date: Fri, 5 May 2017 07:43:18 -0400 (EDT)

----- Original Message -----
> From: "Hari Bathini" <[email-masked]>
> To: "Michael Ellerman" <[email-masked]>
> Cc: "linuxppc-dev" <[email-masked]>, "Pingfan Liu" <[email-masked]>, "Mahesh J Salgaonkar"
> <[email-masked]>
> Sent: Friday, May 5, 2017 1:54:05 AM
> Subject: [PATCH 2/2] powerpc/fadump: avoid holes in boot memory area when fadump is registered
> 
> To register fadump, boot memory area - the size of low memory chunk that
> is required for a kernel to boot successfully when booted with restricted
> memory, is assumed to have no holes. But this memory area is currently

The continuous is required by fadump code, not by the firmware itself, right?

Thanks and regards,
Pingfan

> not protected from hot-remove operations. So, fadump could fail to
> re-register after a memory hot-remove operation, if memory is removed
> from boot memory area. To avoid this, ensure that memory from boot
> memory area is not hot-removed when fadump is registered.
> 
> Signed-off-by: Hari Bathini <[email-masked]>
> ---
>  arch/powerpc/include/asm/fadump.h               |    1 +
>  arch/powerpc/kernel/fadump.c                    |   12 ++++++++++++
>  arch/powerpc/platforms/pseries/hotplug-memory.c |    7 +++++++
>  3 files changed, 20 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/fadump.h
> b/arch/powerpc/include/asm/fadump.h
> index 0031806..609fccc 100644
> --- a/arch/powerpc/include/asm/fadump.h
> +++ b/arch/powerpc/include/asm/fadump.h
> @@ -198,6 +198,7 @@ struct fad_crash_memory_ranges {
>  	unsigned long long	size;
>  };
>  
> +extern int is_fadump_boot_memory_area(u64 addr, ulong size);
>  extern int early_init_dt_scan_fw_dump(unsigned long node,
>  		const char *uname, int depth, void *data);
>  extern int fadump_reserve_mem(void);
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 03563c6..ea7dfdc 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -114,6 +114,18 @@ int __init early_init_dt_scan_fw_dump(unsigned long
> node,
>  	return 1;
>  }
>  
> +/*
> + * If fadump is registered, check if the memory provided
> + * falls within boot memory area.
> + */
> +int is_fadump_boot_memory_area(u64 addr, ulong size)
> +{
> +	if (!fw_dump.dump_registered)
> +		return 0;
> +
> +	return (addr + size) > RMA_START && addr <= fw_dump.boot_memory_size;
> +}
> +
>  int is_fadump_active(void)
>  {
>  	return fw_dump.dump_active;
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c
> b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index e104c71..a186b8e 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -22,6 +22,7 @@
>  #include <asm/machdep.h>
>  #include <asm/prom.h>
>  #include <asm/sparsemem.h>
> +#include <asm/fadump.h>
>  #include "pseries.h"
>  
>  static bool rtas_hp_event;
> @@ -406,6 +407,12 @@ static bool lmb_is_removable(struct of_drconf_cell *lmb)
>  	scns_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
>  	phys_addr = lmb->base_addr;
>  
> +#ifdef CONFIG_FA_DUMP
> +	/* Don't hot-remove memory that falls in fadump boot memory area */
> +	if (is_fadump_boot_memory_area(phys_addr, block_sz))
> +		return false;
> +#endif
> +
>  	for (i = 0; i < scns_per_block; i++) {
>  		pfn = PFN_DOWN(phys_addr);
>  		if (!pfn_present(pfn))
> 
>