On 2025-01-23 15:26, Hari Bathini wrote:
On 20/01/25 11:05 pm, 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.
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.
IIRC, even memory above MIN_RMA is used by the bootloader except for
640MB to 768MB (assuming RMA size is >768MB). So, how does this change
guarantee that the bootloader is not using memory reserved for
bootargs?
Avnish, earlier, bootloader was using RUNTIME_MIN_SPACE (128MB)
starting
top-down at 768MB earlier. With MIN_RMA changed to 768MB, is bootloader
still using the concept of RUNTIME_MIN_SPACE to set aside some memory
for kernel to use. If yes, where exactly is it allocating this space
now? Also, rtas instantiates top-down at 768MB. Would that not have
a conflict with grub allocations without RUNTIME_MIN_SPACE at 768MB?
- Hari
Hi Hari,
The RUNTIME_MIN_SPACE is the space left aside by Grub is within the
MIN_RMA size. Grub won't use memory beyond the MIN_RMA. With this
change, we haven't changed the RUNTIME_MIN_SPACE behavior. Grub will
still keep the 128 MB space in MIN_RMA for loading stock kernel and
initrd.
For your RTAS query, as it gets initiated just below the MIN_RMA. So it
will not have any impact with this RMA size change.
**
When MIN_RMA is 768MB, rtas will be instantiate at 0x000000002ec50000
(approximately at 748 MB).
**
Thank you!
Regards,
Avnish Chouhan
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);
}
fw_dump.param_area = memblock_phys_alloc_range(COMMAND_LINE_SIZE,
