[for 5.10.y] Please revert "8af1c121b0102 riscv: Sparse-Memory/vmemmap out-of-bounds fix"

[for 5.10.y] Please revert "8af1c121b0102 riscv: Sparse-Memory/vmemmap out-of-bounds fix"

[nobuhiro.iwamatsu.x90]

Hi Greg and Sasha,

Please revert "8af1c121b0102 riscv: Sparse-Memory/vmemmap out-of-bounds fix" in Linux-5.10.y branch.
Since `phys_ram_base` is not defined in riscv, a build error will occur if `CONFIG_SPARSEMEM_MANUAL=y`.

```
[...]
                 from arch/riscv/kernel/soc.c:7:
./arch/riscv/include/asm/pgtable-64.h: In function ‘pud_page’:
./arch/riscv/include/asm/pgtable.h:47:58: error: ‘phys_ram_base’ undeclared (first use in this function)
   47 | #define vmemmap         ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT))
      |                                                          ^~~~~~~~~~~~~
./include/asm-generic/memory_model.h:54:34: note: in expansion of macro ‘vmemmap’
   54 | #define __pfn_to_page(pfn)      (vmemmap + (pfn))
      |                                  ^~~~~~~
./include/asm-generic/memory_model.h:82:21: note: in expansion of macro ‘__pfn_to_page’
   82 | #define pfn_to_page __pfn_to_page
      |                     ^~~~~~~~~~~~~
./arch/riscv/include/asm/pgtable-64.h:70:16: note: in expansion of macro ‘pfn_to_page’
   70 |         return pfn_to_page(pud_val(pud) >> _PAGE_PFN_SHIFT);
      |                ^~~~~~~~~~~
./arch/riscv/include/asm/pgtable.h:47:58: note: each undeclared identifier is reported only once for each function it appears in
   47 | #define vmemmap         ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT))
      |                                                          ^~~~~~~~~~~~~
./include/asm-generic/memory_model.h:54:34: note: in expansion of macro ‘vmemmap’
   54 | #define __pfn_to_page(pfn)      (vmemmap + (pfn))
      |                                  ^~~~~~~
./include/asm-generic/memory_model.h:82:21: note: in expansion of macro ‘__pfn_to_page’
   82 | #define pfn_to_page __pfn_to_page
      |                     ^~~~~~~~~~~~~
./arch/riscv/include/asm/pgtable-64.h:70:16: note: in expansion of macro ‘pfn_to_page’
   70 |         return pfn_to_page(pud_val(pud) >> _PAGE_PFN_SHIFT);
      |                ^~~~~~~~~~~
  AS      arch/riscv/kernel/vdso/flush_icache.o
./arch/riscv/include/asm/pgtable.h: In function ‘pmd_page’:
./arch/riscv/include/asm/pgtable.h:47:58: error: ‘phys_ram_base’ undeclared (first use in this function)
   47 | #define vmemmap         ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT))
      |                                                          ^~~~~~~~~~~~~
./include/asm-generic/memory_model.h:54:34: note: in expansion of macro ‘vmemmap’
   54 | #define __pfn_to_page(pfn)      (vmemmap + (pfn))
      |                                  ^~~~~~~
./include/asm-generic/memory_model.h:82:21: note: in expansion of macro ‘__pfn_to_page’
   82 | #define pfn_to_page __pfn_to_page
      |                     ^~~~~~~~~~~~~
./arch/riscv/include/asm/pgtable.h:181:16: note: in expansion of macro ‘pfn_to_page’
  181 |         return pfn_to_page(pmd_val(pmd) >> _PAGE_PFN_SHIFT);
      |                ^~~~~~~~~~~                                                        ^~~~~~~~~~~~~
[...]
```

Best regards,
  Nobuhiro

Re: [for 5.10.y] Please revert "8af1c121b0102 riscv: Sparse-Memory/vmemmap out-of-bounds fix"

[Greg KH]

On Wed, Mar 18, 2026 at 02:03:44AM +0000, nobuhiro.iwamatsu.x90@mail.toshiba wrote:
> Hi Greg and Sasha,
> 
> Please revert "8af1c121b0102 riscv: Sparse-Memory/vmemmap out-of-bounds fix" in Linux-5.10.y branch.
> Since `phys_ram_base` is not defined in riscv, a build error will occur if `CONFIG_SPARSEMEM_MANUAL=y`.


Can you send a revert with this information in it?

thanks,

greg k-h