Re: [PATCH v4 2/2] RISC-V: Implement sparsemem

[Greentime Hu]

Hi Logan,

On Thu, Aug 15, 2019 at 6:21 AM Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote:
>
> Hey,
>
> On 2019-08-14 7:35 a.m., Greentime Hu wrote:
> > How about this fix? Not sure if it is good for everyone.
>
> I applied your fix to the patch and it seems ok. But it doesn't seem to
> work on a recent version of the kernel. Have you got it working on v5.3?
> It seems the following patch breaks things:
>
> 671f9a3e2e24 ("RISC-V: Setup initial page tables in two stages")
>
> I don't really have time right now to debug this any further.
>

I just tried v5.3-rc4 and it failed. I try to debug this case.
I found it failed might be because of an unmapped virtual address is used
in memblocks_present() -> memblock_alloc ().

In this commit 671f9a3e2e24 ("RISC-V: Setup initial page tables in two
stages"), it finishes all the VA/PA mapping after setup_vm_final() is
called.
So we have to call memblocks_present() and sparse_init() right after
setup_vm_final().

Here is my patch and I tested with memory-with-hole.
It can boot normally in Unleashed board after applying this patch.

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 27d1d847fb2d..35aacb0c93e5 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -138,8 +138,6 @@ void __init setup_bootmem(void)
                                  PFN_PHYS(end_pfn - start_pfn),
                                  &memblock.memory, 0);
        }
-       memblocks_present();
-       sparse_init();
 }

 unsigned long va_pa_offset;
@@ -452,6 +450,8 @@ static void __init setup_vm_final(void)
 void __init paging_init(void)
 {
        setup_vm_final();
+       memblocks_present();
+       sparse_init();
        setup_zero_page();
        zone_sizes_init();
 }

Test case:
memory@80000000 {
        device_type = "memory";
        reg = <0x0 0x80000000 0x0 0x80000000>;
};
memory@180000000 {
        device_type = "memory";
        reg = <0x1 0x80000000 0x0 0x40000000>;
};


# cat /proc/meminfo
MemTotal:        3003496 kB
MemFree:         2986584 kB
MemAvailable:    2970176 kB
Buffers:               0 kB
Cached:             3540 kB
SwapCached:            0 kB
Active:             3920 kB
Inactive:             68 kB
Active(anon):       3920 kB
Inactive(anon):       68 kB
Active(file):          0 kB
Inactive(file):        0 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:           528 kB
Mapped:             1984 kB
Shmem:              3540 kB
KReclaimable:        688 kB
Slab:               5700 kB
SReclaimable:        688 kB
SUnreclaim:         5012 kB
KernelStack:         424 kB
PageTables:           80 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     1501748 kB
Committed_AS:       3200 kB
VmallocTotal:   67108863 kB
VmallocUsed:          12 kB
VmallocChunk:          0 kB
Percpu:              272 kB
# uname -a
Linux buildroot 5.3.0-rc4-00001-g44404421c481-dirty #10 SMP Thu Aug 15
16:28:24 DST 2019 riscv64 GNU/Lin[ 2352.443621] random: fast init done
ux
# zcat /proc/config.gz |grep SPARSE
CONFIG_SPARSE_IRQ=y
CONFIG_ARCH_SPARSEMEM_ENABLE=y
CONFIG_SPARSEMEM_MANUAL=y
CONFIG_SPARSEMEM=y
CONFIG_SPARSEMEM_EXTREME=y
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
CONFIG_SPARSEMEM_VMEMMAP=y
# CONFIG_INPUT_SPARSEKMAP is not set