On 2025-01-20 23:05:00 Mon, Sourabh Jain wrote:
> Commit 683eab94da75bc ("powerpc/fadump: setup additional parameters for
> dump capture kernel") introduced the additional parameter feature in
> fadump for HASH MMU with the understanding that GRUB does not use the
> memory area between 640MB and 768MB for its operation.
>
> However, the patch ("powerpc: increase MIN RMA size for CAS
> negotiation") changes the MIN RMA size to 768MB, allowing GRUB to use
> memory up to 768MB. This makes the fadump reservation for the additional
> parameter feature for HASH MMU unreliable.
I see. Please include above patch in single patch series, with this
change as first patch.
>
> To address this, adjust the memory range for the additional parameter in
> fadump for HASH MMU. This will ensure that GRUB does not overwrite the
> memory reserved for fadump's additional parameter in HASH MMU.
>
> The new policy for the memory range for the additional parameter in HASH
> MMU is that the first memory block must be larger than the MIN_RMA size,
> as the bootloader can use memory up to the MIN_RMA size. The range
> should be between MIN_RMA and the RMA size (ppc64_rma_size), and it must
> not overlap with the fadump reserved area.
>
> Cc: Avnish Chouhan <avn...@linux.ibm.com>
> Cc: Brian King <brk...@linux.ibm.com>
> Cc: Hari Bathini <hbath...@linux.ibm.com>
> Cc: Madhavan Srinivasan <ma...@linux.ibm.com>
> Cc: Michael Ellerman <m...@ellerman.id.au>
> Cc: Mahesh Salgaonkar <mah...@linux.ibm.com>
> Signed-off-by: Sourabh Jain <sourabhj...@linux.ibm.com>
> ---
> arch/powerpc/kernel/fadump.c | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 4b371c738213..5831f3ec8561 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -33,6 +33,7 @@
> #include <asm/fadump-internal.h>
> #include <asm/setup.h>
> #include <asm/interrupt.h>
> +#include <asm/prom.h>
>
> /*
> * The CPU who acquired the lock to trigger the fadump crash should
> @@ -1764,19 +1765,19 @@ void __init fadump_setup_param_area(void)
> range_end = memblock_end_of_DRAM();
> } else {
> /*
> - * Passing additional parameters is supported for hash MMU only
> - * if the first memory block size is 768MB or higher.
> + * Memory range for passing additional parameters for HASH MMU
> + * must meet the following conditions:
> + * 1. The first memory block size must be higher than the
> + * minimum RMA (MIN_RMA) size. Bootloader can use memory
> + * up to RMA size. So it should be avoided.
> + * 2. The range should be between MIN_RMA and RMA size
> (ppc64_rma_size)
> + * 3. It must not overlap with the fadump reserved area.
> */
> - if (ppc64_rma_size < 0x30000000)
> + if (ppc64_rma_size < MIN_RMA*1024*1024)
> return;
>
> - /*
> - * 640 MB to 768 MB is not used by PFW/bootloader. So, try
> reserving
> - * memory for passing additional parameters in this range to
> avoid
> - * being stomped on by PFW/bootloader.
> - */
> - range_start = 0x2A000000;
> - range_end = range_start + 0x4000000;
> + range_start = MIN_RMA * 1024 * 1024;
> + range_end = min(ppc64_rma_size, fw_dump.boot_mem_top);
Please update fadump documentation which makes this restriction clear.
Rest looks good to me.
Reviewed-by: Mahesh Salgaonkar <mah...@linux.ibm.com>
Thanks,
-Mahesh
