On 01/04/19 at 04:39pm, Pingfan Liu wrote: > Customer reported a bug on a high end server with many pcie devices, where > kernel bootup with crashkernel=384M, and kaslr is enabled. Even > though we still see much memory under 896 MB, the finding still failed > intermittently. Because currently we can only find region under 896 MB, > if w/0 ',high' specified. Then KASLR breaks 896 MB into several parts > randomly, and crashkernel reservation need be aligned to 128 MB, that's > why failure is found. It raises confusion to the end user that sometimes > crashkernel=X works while sometimes fails. > If want to make it succeed, customer can change kernel option to > "crashkernel=384M, high". Just this give "crashkernel=xx@yy" a very > limited space to behave even though its grammer looks more generic. > And we can't answer questions raised from customer that confidently: > 1) why it doesn't succeed to reserve 896 MB; > 2) what's wrong with memory region under 4G; > 3) why I have to add ',high', I only require 384 MB, not 3840 MB. > > This patch simplifies the method suggested in the mail [1]. It just goes > bottom-up to find a candidate region for crashkernel. The bottom-up may be > better compatible with the old reservation style, i.e. still want to get > memory region from 896 MB firstly, then [896 MB, 4G], finally above 4G. > > There is one trivial thing about the compatibility with old kexec-tools: > if the reserved region is above 896M, then old tool will fail to load > bzImage. But without this patch, the old tool also fail since there is no > memory below 896M can be reserved for crashkernel. > > [1]: http://lists.infradead.org/pipermail/kexec/2017-October/019571.html > Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> > Cc: Len Brown <lenb@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Jonathan Corbet <corbet@xxxxxxx> > Cc: Yaowei Bai <baiyaowei@xxxxxxxxxxxxxxxxxxxx> > Cc: Nicholas Piggin <npiggin@xxxxxxxxx> > Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Cc: Daniel Vacek <neelx@xxxxxxxxxx> > Cc: Mathieu Malaterre <malat@xxxxxxxxxx> > Cc: Stefan Agner <stefan@xxxxxxxx> > Cc: Dave Young <dyoung@xxxxxxxxxx> > Cc: Baoquan He <bhe@xxxxxxxxxx> > Cc: yinghai@xxxxxxxxxx > Cc: vgoyal@xxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > --- > v3 -> v4: > instead of exporting the stage of parsing mem hotplug info, just using the bottom-up allocation func directly > arch/x86/kernel/setup.c | 8 ++++---- > include/linux/memblock.h | 4 ++++ > mm/memblock.c | 2 +- > 3 files changed, 9 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index d494b9b..082aadd 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -546,10 +546,10 @@ static void __init reserve_crashkernel(void) > * as old kexec-tools loads bzImage below that, unless > * "crashkernel=size[KMG],high" is specified. > */ > - crash_base = memblock_find_in_range(CRASH_ALIGN, > - high ? CRASH_ADDR_HIGH_MAX > - : CRASH_ADDR_LOW_MAX, > - crash_size, CRASH_ALIGN); > + crash_base = __memblock_find_range_bottom_up(CRASH_ALIGN, Better make a wrapper function for external invocation. E.g we need allocate kernel data in mirrorred memory region if it's available. This has been done in memblock_find_in_range(), and the boundary alignment. > + (max_pfn * PAGE_SIZE), crash_size, CRASH_ALIGN, > + NUMA_NO_NODE, MEMBLOCK_NONE); > + > if (!crash_base) { > pr_info("crashkernel reservation failed - No suitable area found.\n"); > return; > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index aee299a..39720bf 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -116,6 +116,10 @@ phys_addr_t memblock_find_in_range_node(phys_addr_t size, phys_addr_t align, > int nid, enum memblock_flags flags); > phys_addr_t memblock_find_in_range(phys_addr_t start, phys_addr_t end, > phys_addr_t size, phys_addr_t align); > +phys_addr_t __init_memblock > +__memblock_find_range_bottom_up(phys_addr_t start, phys_addr_t end, > + phys_addr_t size, phys_addr_t align, int nid, > + enum memblock_flags flags); > void memblock_allow_resize(void); > int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid); > int memblock_add(phys_addr_t base, phys_addr_t size); > diff --git a/mm/memblock.c b/mm/memblock.c > index 81ae63c..53b1707 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -172,7 +172,7 @@ bool __init_memblock memblock_overlaps_region(struct memblock_type *type, > * Return: > * Found address on success, 0 on failure. > */ > -static phys_addr_t __init_memblock > +phys_addr_t __init_memblock > __memblock_find_range_bottom_up(phys_addr_t start, phys_addr_t end, > phys_addr_t size, phys_addr_t align, int nid, > enum memblock_flags flags) > -- > 2.7.4 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
