Can we put this in a common header somewhere? Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: >On Wed, 25 Sep 2013 02:30:51 +0800 Zhang Yanfei ><zhangyanfei.yes@xxxxxxxxx> wrote: > >> From: Tang Chen <tangchen@xxxxxxxxxxxxxx> >> >> The Linux kernel cannot migrate pages used by the kernel. As a >> result, kernel pages cannot be hot-removed. So we cannot allocate >> hotpluggable memory for the kernel. >> >> In a memory hotplug system, any numa node the kernel resides in >> should be unhotpluggable. And for a modern server, each node could >> have at least 16GB memory. So memory around the kernel image is >> highly likely unhotpluggable. >> >> ACPI SRAT (System Resource Affinity Table) contains the memory >> hotplug info. But before SRAT is parsed, memblock has already >> started to allocate memory for the kernel. So we need to prevent >> memblock from doing this. >> >> So direct memory mapping page tables setup is the case. >init_mem_mapping() >> is called before SRAT is parsed. To prevent page tables being >allocated >> within hotpluggable memory, we will use bottom-up direction to >allocate >> page tables from the end of kernel image to the higher memory. >> >> ... >> >> + kernel_end = __pa_symbol(_end); > >__pa_symbol() is implemented only on mips and x86. > >I stole the mips implementation like this: > >--- a/mm/memblock.c~a >+++ a/mm/memblock.c >@@ -187,8 +187,11 @@ phys_addr_t __init_memblock memblock_fin > /* avoid allocating the first page */ > start = max_t(phys_addr_t, start, PAGE_SIZE); > end = max(start, end); >+#ifdef CONFIG_X86 > kernel_end = __pa_symbol(_end); >- >+#else >+ kernel_end = __pa(RELOC_HIDE((unsigned long)(_end), 0)); >+#endif > /* > * try bottom-up allocation only when bottom-up mode > * is set and @end is above the kernel image. > >just so I can get a -mm release out the door. -- Sent from my mobile phone. Please pardon brevity and lack of formatting. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>