Hi Baoquan, On 04/28/2015 06:19 PM, Baoquan He wrote: >> +#ifdef CONFIG_CRASH_DUMP >> +/* >> + * reserve_elfcorehdr() - reserves memory for elf core header >> + * >> + * This function reserves memory area given in "elfcorehdr=" kernel command >> + * line parameter. The memory reserved is used by a dump capture kernel to >> + * identify the memory used by primary kernel. >> + */ > > Hi AKASHI, > > May I know why elfcorehdr need be reserved separately but not locate a > memory region in crashkernel reserved region like all other ARCHs? Is > there any special reason? I don't get your point, but arm as well as arm64 locates elfcorehdr in a crash kernel's memory region. See kexec/arch/arm{,64}/crashdump-arm{,64}.c in kexec-tools. And this region is reserved at boot time *on crash kernel* because we don't want to corrupt it accidentally. (After Mark's comment, we might better remove the mmu mapping for this region, too.) Make sense? -Takahiro AKASHI > Thanks > Baoquan > >> +static void __init reserve_elfcorehdr(void) >> +{ >> + if (!elfcorehdr_size) >> + return; >> + >> + if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) { >> + pr_warn("elfcorehdr reservation failed - memory is in use (0x%llx)\n", >> + elfcorehdr_addr); >> + return; >> + } >> + >> + if (memblock_reserve(elfcorehdr_addr, elfcorehdr_size)) { >> + pr_warn("elfcorehdr reservation failed - out of memory\n"); >> + return; >> + } >> + >> + pr_info("Reserving %lldKB of memory at %lldMB for elfcorehdr\n", >> + elfcorehdr_size >> 10, elfcorehdr_addr >> 20); >> +} >> +#endif /* CONFIG_CRASH_DUMP */ >> /* >> * Return the maximum physical address for ZONE_DMA (DMA_BIT_MASK(32)). It >> * currently assumes that for memory starting above 4G, 32-bit devices will >> @@ -170,6 +247,13 @@ void __init arm64_memblock_init(void) >> memblock_reserve(__virt_to_phys(initrd_start), initrd_end - initrd_start); >> #endif >> >> +#ifdef CONFIG_KEXEC >> + reserve_crashkernel(memory_limit); >> +#endif >> +#ifdef CONFIG_CRASH_DUMP >> + reserve_elfcorehdr(); >> +#endif >> + >> early_init_fdt_scan_reserved_mem(); >> >> /* 4GB maximum for 32-bit only capable devices */ >> -- >> 1.7.9.5 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo at vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/