[PATCH v3 6/7] powerpc/fadump: Do not allow hot-remove memory from fadump reserved area.

[Pingfan Liu]

I think CMA has protected us from hot-remove, so this patch is not necessary.

Regards,
Pingfan

On Mon, Apr 2, 2018 at 2:30 PM, Mahesh J Salgaonkar
<mahesh at linux.vnet.ibm.com> wrote:
> From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
>
> For fadump to work successfully there should not be any holes in reserved
> memory ranges where kernel has asked firmware to move the content of old
> kernel memory in event of crash. But this memory area is currently not
> protected from hot-remove operations. Hence, fadump service can fail to
> re-register after the hot-remove operation, if hot-removed memory belongs
> to fadump reserved region. To avoid this make sure that memory from fadump
> reserved area is not hot-removable if fadump is registered.
>
> However, if user still wants to remove that memory, he can do so by
> manually stopping fadump service before hot-remove operation.
>
> Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> ---
>  arch/powerpc/include/asm/fadump.h               |    2 +-
>  arch/powerpc/kernel/fadump.c                    |   10 ++++++++--
>  arch/powerpc/platforms/pseries/hotplug-memory.c |    7 +++++--
>  3 files changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/fadump.h b/arch/powerpc/include/asm/fadump.h
> index 44b6ebfe9be6..d16dc77107a8 100644
> --- a/arch/powerpc/include/asm/fadump.h
> +++ b/arch/powerpc/include/asm/fadump.h
> @@ -207,7 +207,7 @@ struct fad_crash_memory_ranges {
>         unsigned long long      size;
>  };
>
> -extern int is_fadump_boot_memory_area(u64 addr, ulong size);
> +extern int is_fadump_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 59aaf0357a52..2c3c7e655eec 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -162,13 +162,19 @@ int __init early_init_dt_scan_fw_dump(unsigned long node,
>
>  /*
>   * If fadump is registered, check if the memory provided
> - * falls within boot memory area.
> + * falls within boot memory area and reserved memory area.
>   */
> -int is_fadump_boot_memory_area(u64 addr, ulong size)
> +int is_fadump_memory_area(u64 addr, ulong size)
>  {
> +       u64 d_start = fw_dump.reserve_dump_area_start;
> +       u64 d_end = d_start + fw_dump.reserve_dump_area_size;
> +
>         if (!fw_dump.dump_registered)
>                 return 0;
>
> +       if (((addr + size) > d_start) && (addr <= d_end))
> +               return 1;
> +
>         return (addr + size) > RMA_START && addr <= fw_dump.boot_memory_size;
>  }
>
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index c1578f54c626..e4c658cda3a7 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -389,8 +389,11 @@ static bool lmb_is_removable(struct drmem_lmb *lmb)
>         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))
> +       /*
> +        * Don't hot-remove memory that falls in fadump boot memory area
> +        * and memory that is reserved for capturing old kernel memory.
> +        */
> +       if (is_fadump_memory_area(phys_addr, block_sz))
>                 return false;
>  #endif
>
>