Message ID | 148717255648.1711.9357297790070400059.stgit@hbathini.in.ibm.com (mailing list archive) |
---|---|
State | Superseded |
Headers | show |
Hari Bathini <hbathini@linux.vnet.ibm.com> writes: > diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c > index de7d39a..d5107f4 100644 > --- a/arch/powerpc/kernel/fadump.c > +++ b/arch/powerpc/kernel/fadump.c > @@ -222,6 +222,18 @@ static inline unsigned long fadump_calculate_reserve_size(void) > &size, &base); > if (ret == 0 && size > 0) { > fw_dump.reserve_bootvar = (unsigned long)size; > + /* > + * Adjust if the boot memory size specified is above > + * the upper limit. > + */ > + if (fw_dump.reserve_bootvar > > + (memblock_end_of_DRAM() / MAX_BOOT_MEM_RATIO)) { Using memblock_end_of_DRAM() doesn't take into account the fact that you might have holes in your memory layout. Possibly on PowerVM that never happens, but I don't think we should write the code to assume that, if possible. cheers
Hi Michael, On Friday 17 February 2017 11:54 AM, Michael Ellerman wrote: > Hari Bathini <hbathini@linux.vnet.ibm.com> writes: > >> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c >> index de7d39a..d5107f4 100644 >> --- a/arch/powerpc/kernel/fadump.c >> +++ b/arch/powerpc/kernel/fadump.c >> @@ -222,6 +222,18 @@ static inline unsigned long fadump_calculate_reserve_size(void) >> &size, &base); >> if (ret == 0 && size > 0) { >> fw_dump.reserve_bootvar = (unsigned long)size; >> + /* >> + * Adjust if the boot memory size specified is above >> + * the upper limit. >> + */ >> + if (fw_dump.reserve_bootvar > >> + (memblock_end_of_DRAM() / MAX_BOOT_MEM_RATIO)) { > Using memblock_end_of_DRAM() doesn't take into account the fact that you > might have holes in your memory layout. > > Possibly on PowerVM that never happens, but I don't think we should > write the code to assume that, if possible. > I think memblock_phys_mem_size() can fill in.. In the same file, memblock_end_of_DRAM() is also used when nothing is specified through cmdline. Let me also change that and respin.. Thanks Hari
diff --git a/arch/powerpc/include/asm/fadump.h b/arch/powerpc/include/asm/fadump.h index 60b9108..a3de219 100644 --- a/arch/powerpc/include/asm/fadump.h +++ b/arch/powerpc/include/asm/fadump.h @@ -43,6 +43,9 @@ #define MIN_BOOT_MEM (((RMA_END < (0x1UL << 28)) ? (0x1UL << 28) : RMA_END) \ + (0x1UL << 26)) +/* The upper limit percentage for user specified boot memory size (25%) */ +#define MAX_BOOT_MEM_RATIO 4 + #define memblock_num_regions(memblock_type) (memblock.memblock_type.cnt) /* Firmware provided dump sections */ diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c index de7d39a..d5107f4 100644 --- a/arch/powerpc/kernel/fadump.c +++ b/arch/powerpc/kernel/fadump.c @@ -222,6 +222,18 @@ static inline unsigned long fadump_calculate_reserve_size(void) &size, &base); if (ret == 0 && size > 0) { fw_dump.reserve_bootvar = (unsigned long)size; + /* + * Adjust if the boot memory size specified is above + * the upper limit. + */ + if (fw_dump.reserve_bootvar > + (memblock_end_of_DRAM() / MAX_BOOT_MEM_RATIO)) { + fw_dump.reserve_bootvar = (memblock_end_of_DRAM() / + MAX_BOOT_MEM_RATIO); + pr_info("Adjusted boot memory size to %luMB\n", + (fw_dump.reserve_bootvar >> 20)); + } + return fw_dump.reserve_bootvar; }
By default, 5% of system RAM is reserved for preserving boot memory. Alternatively, a user can specify the amount of memory to reserve. See Documentation/powerpc/firmware-assisted-dump.txt for details. In addition to the memory reserved for preserving boot memory, some more memory is reserved, to save HPTE region, CPU state data and ELF core headers. Memory Reservation during first kernel looks like below: Low memory Top of memory 0 boot memory size | | | |<--Reserved dump area -->| V V | Permanent Reservation V +-----------+----------/ /----------+---+----+-----------+----+ | | |CPU|HPTE| DUMP |ELF | +-----------+----------/ /----------+---+----+-----------+----+ | ^ | | \ / ------------------------------------------- Boot memory content gets transferred to reserved area by firmware at the time of crash The implicit rule here is that the sum of the sizes of boot memory, CPU state data, HPTE region and ELF core headers can't be greater than the total memory size. But currently, a user is allowed to specify any value as boot memory size. So, the above rule is violated when a boot memory size closer to 50% of the total available memory is specified. As the kernel is not handling this currently, it may lead to undefined behavior. Fix it by setting an upper limit for boot memory size to 25% of the total available memory. Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com> --- This patch is based on top of reuse-crashkernel-parameter-for-fadump patchset (https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-January/152724.html) arch/powerpc/include/asm/fadump.h | 3 +++ arch/powerpc/kernel/fadump.c | 12 ++++++++++++ 2 files changed, 15 insertions(+)