Hi, On Fri, Apr 05, 2019 at 11:47:27AM +0800, Chen Zhou wrote: > Hi Mike, > > On 2019/4/5 10:17, Chen Zhou wrote: > > Hi Mike, > > > > On 2019/4/4 22:44, Mike Rapoport wrote: > >> Hi, > >> > >> On Wed, Apr 03, 2019 at 09:51:27PM +0800, Chen Zhou wrote: > >>> Hi Mike, > >>> > >>> On 2019/4/3 19:29, Mike Rapoport wrote: > >>>> On Wed, Apr 03, 2019 at 11:05:45AM +0800, Chen Zhou wrote: > >>>>> After commit (arm64: kdump: support reserving crashkernel above 4G), > >>>>> there may be two crash kernel regions, one is below 4G, the other is > >>>>> above 4G. > >>>>> > >>>>> Crash dump kernel reads more than one crash kernel regions via a dtb > >>>>> property under node /chosen, > >>>>> linux,usable-memory-range = <BASE1 SIZE1 [BASE2 SIZE2]> > >>>>> > >>>>> Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx> > >>>>> --- > >>>>> arch/arm64/mm/init.c | 37 +++++++++++++++++++++++++------------ > >>>>> include/linux/memblock.h | 1 + > >>>>> mm/memblock.c | 40 ++++++++++++++++++++++++++++++++++++++++ > >>>>> 3 files changed, 66 insertions(+), 12 deletions(-) > >>>>> > >>>>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > >>>>> index ceb2a25..769c77a 100644 > >>>>> --- a/arch/arm64/mm/init.c > >>>>> +++ b/arch/arm64/mm/init.c > >>>>> @@ -64,6 +64,8 @@ EXPORT_SYMBOL(memstart_addr); > >>>>> phys_addr_t arm64_dma_phys_limit __ro_after_init; > >>>>> > >>>>> #ifdef CONFIG_KEXEC_CORE > >>>>> +# define CRASH_MAX_USABLE_RANGES 2 > >>>>> + > >>>>> static int __init reserve_crashkernel_low(void) > >>>>> { > >>>>> unsigned long long base, low_base = 0, low_size = 0; > >>>>> @@ -346,8 +348,8 @@ static int __init early_init_dt_scan_usablemem(unsigned long node, > >>>>> const char *uname, int depth, void *data) > >>>>> { > >>>>> struct memblock_region *usablemem = data; > >>>>> - const __be32 *reg; > >>>>> - int len; > >>>>> + const __be32 *reg, *endp; > >>>>> + int len, nr = 0; > >>>>> > >>>>> if (depth != 1 || strcmp(uname, "chosen") != 0) > >>>>> return 0; > >>>>> @@ -356,22 +358,33 @@ static int __init early_init_dt_scan_usablemem(unsigned long node, > >>>>> if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells))) > >>>>> return 1; > >>>>> > >>>>> - usablemem->base = dt_mem_next_cell(dt_root_addr_cells, ®); > >>>>> - usablemem->size = dt_mem_next_cell(dt_root_size_cells, ®); > >>>>> + endp = reg + (len / sizeof(__be32)); > >>>>> + while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) { > >>>>> + usablemem[nr].base = dt_mem_next_cell(dt_root_addr_cells, ®); > >>>>> + usablemem[nr].size = dt_mem_next_cell(dt_root_size_cells, ®); > >>>>> + > >>>>> + if (++nr >= CRASH_MAX_USABLE_RANGES) > >>>>> + break; > >>>>> + } > >>>>> > >>>>> return 1; > >>>>> } > >>>>> > >>>>> static void __init fdt_enforce_memory_region(void) > >>>>> { > >>>>> - struct memblock_region reg = { > >>>>> - .size = 0, > >>>>> - }; > >>>>> - > >>>>> - of_scan_flat_dt(early_init_dt_scan_usablemem, ®); > >>>>> - > >>>>> - if (reg.size) > >>>>> - memblock_cap_memory_range(reg.base, reg.size); > >>>>> + int i, cnt = 0; > >>>>> + struct memblock_region regs[CRASH_MAX_USABLE_RANGES]; > >>>>> + > >>>>> + memset(regs, 0, sizeof(regs)); > >>>>> + of_scan_flat_dt(early_init_dt_scan_usablemem, regs); > >>>>> + > >>>>> + for (i = 0; i < CRASH_MAX_USABLE_RANGES; i++) > >>>>> + if (regs[i].size) > >>>>> + cnt++; > >>>>> + else > >>>>> + break; > >>>>> + if (cnt) > >>>>> + memblock_cap_memory_ranges(regs, cnt); > >>>> > >>>> Why not simply call memblock_cap_memory_range() for each region? > >>> > >>> Function memblock_cap_memory_range() removes all memory type ranges except specified range. > >>> So if we call memblock_cap_memory_range() for each region simply, there will be no usable-memory > >>> on kdump capture kernel. > >> > >> Thanks for the clarification. > >> I still think that memblock_cap_memory_ranges() is overly complex. > >> > >> How about doing something like this: > >> > >> Cap the memory range for [min(regs[*].start, max(regs[*].end)] and then > >> removing the range in the middle? > > > > Yes, that would be ok. But that would do one more memblock_cap_memory_range operation. > > That is, if there are n regions, we need to do (n + 1) operations, which doesn't seem to > > matter. > > > > I agree with you, your idea is better. > > > > Thanks, > > Chen Zhou > > Sorry, just ignore my previous reply, I got that wrong. > > I think it carefully, we can cap the memory range for [min(regs[*].start, max(regs[*].end)] > firstly. But how to remove the middle ranges, we still can't use memblock_cap_memory_range() > directly and the extra remove operation may be complex. > > For more than one regions, i think add a new memblock_cap_memory_ranges() may be better. > Besides, memblock_cap_memory_ranges() is also applicable for one region. > > How about replace memblock_cap_memory_range() with memblock_cap_memory_ranges()? arm64 is the only user of both MEMBLOCK_NOMAP and memblock_cap_memory_range() and I don't expect other architectures will use these interfaces. It seems that capping the memory for arm64 crash kernel the way I've suggested can be implemented in fdt_enforce_memory_region(). If we'd ever need such functionality elsewhere or CRASH_MAX_USABLE_RANGES will need to grow we'll rethink the solution. > Thanks, > Chen Zhou -- Sincerely yours, Mike. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec