Messages in this thread | | | From | Atish Patra <> | Date | Mon, 14 Sep 2020 10:53:00 -0700 | Subject | Re: [PATCH] RISC-V: Consider sparse memory while removing unusable memory |
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On Mon, Sep 14, 2020 at 4:52 AM Anup Patel <anup@brainfault.org> wrote: > > On Mon, Sep 14, 2020 at 5:18 AM Atish Patra <atishp@atishpatra.org> wrote: > > > > On Sat, Sep 12, 2020 at 3:45 AM Mike Rapoport <rppt@kernel.org> wrote: > > > > > > Hello Atish, > > > > > > On Fri, Sep 11, 2020 at 05:23:41PM -0700, Atish Patra wrote: > > > > Currently, any usable memory area beyond page_offset is removed by adding the > > > > memory sizes from each memblock. That may not work for sparse memory > > > > as memory regions can be very far apart resulting incorrect removal of some > > > > usable memory. > > > > > > If I understand correctly, the memory with physical addresses larger > > > than (-PAGE_OFFSET) cannot be used. Since it was aready > > > memblock_add()'ed during device tree parsing, you need to remove it from > > > memblock. > > > > > > > IIRC, the original intention was to fix MAXPHYSMEM_2GB option for RV64 > > for the medlow model. > > That's why the patch removed any memory beyond -PAGE_OFFSET. > > > > > For that you can use memblock_enforce_memory_limit(-PAGE_OFFSET). > > > > > Thanks. I think we can just call memblock_enforce_memory_limit without > > tracking the total memory size > > and whether maximum memory described in DT is greater than -PAGE_OFFSET. > > > > @Anup Patel Was there any other reason for this change originally? > > No other reason. We just wanted to ensure that amount of memory addressable > by kernel (i.e. -PAGE_OFFSET) is also considered when removing memblock. >
It looks like we have an agreement here then. I will update the patch to directly call memblock_enforce_memory_limit as suggested by Mike.
> Regards, > Anup > > > > > > > Just use the start of the first memory block and the end of the last memory > > > > block to compute the size of the total memory that can be used. > > > > > > > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > > > > --- > > > > arch/riscv/mm/init.c | 6 ++---- > > > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > > > > index 787c75f751a5..188281fc2816 100644 > > > > --- a/arch/riscv/mm/init.c > > > > +++ b/arch/riscv/mm/init.c > > > > @@ -147,7 +147,6 @@ void __init setup_bootmem(void) > > > > { > > > > struct memblock_region *reg; > > > > phys_addr_t mem_size = 0; > > > > - phys_addr_t total_mem = 0; > > > > phys_addr_t mem_start, end = 0; > > > > phys_addr_t vmlinux_end = __pa_symbol(&_end); > > > > phys_addr_t vmlinux_start = __pa_symbol(&_start); > > > > @@ -155,18 +154,17 @@ void __init setup_bootmem(void) > > > > /* Find the memory region containing the kernel */ > > > > for_each_memblock(memory, reg) { > > > > end = reg->base + reg->size; > > > > - if (!total_mem) > > > > + if (!mem_start) > > > > mem_start = reg->base; > > > > if (reg->base <= vmlinux_start && vmlinux_end <= end) > > > > BUG_ON(reg->size == 0); > > > > - total_mem = total_mem + reg->size; > > > > } > > > > > > > > /* > > > > * Remove memblock from the end of usable area to the > > > > * end of region > > > > */ > > > > - mem_size = min(total_mem, (phys_addr_t)-PAGE_OFFSET); > > > > + mem_size = min(end - mem_start, (phys_addr_t)-PAGE_OFFSET); > > > > if (mem_start + mem_size < end) > > > > memblock_remove(mem_start + mem_size, > > > > end - mem_start - mem_size); > > > > -- > > > > 2.24.0 > > > > > > > > > > -- > > > Sincerely yours, > > > Mike. > > > > > > _______________________________________________ > > > linux-riscv mailing list > > > linux-riscv@lists.infradead.org > > > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > > > > > -- > > Regards, > > Atish
-- Regards, Atish
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