Re: [PATCH] riscv: patch: Avoid early page_to_phys()

[Mike Rapoport]

On Tue, Mar 10, 2026 at 04:25:33PM +0800, Vivian Wang wrote:
> Similarly to commit 8d09e2d569f6 ("arm64: patching: avoid early
> page_to_phys()"), avoid using phys_to_page() for the kernel address case
> in patch_map().
> 
> Since this is called from apply_boot_alternatives() in setup_arch(), and
> commit 4267739cabb8 ("arch, mm: consolidate initialization of SPARSE
> memory model") has moved sparse_init() to after setup_arch(),
> phys_to_page() is not available there yet, and it panics on boot with
> SPARSEMEM on RV32, which does not use SPARSEMEM_VMEMMAP.
> 
> Reported-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/r/20260223144108-dcace0b9-02e8-4b67-a7ce-f263bed36f26@xxxxxxxxxxxxx/
> Fixes: 4267739cabb8 ("arch, mm: consolidate initialization of SPARSE memory model")
> Suggested-by: Mike Rapoport <rppt@xxxxxxxxxx>

Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>

> Signed-off-by: Vivian Wang <wangruikang@xxxxxxxxxxx>
> ---
> checkpatch.pl complains about the BUG_ON which was already there
> ---
>  arch/riscv/kernel/patch.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> index db13c9ddf9e3..16b243376f36 100644
> --- a/arch/riscv/kernel/patch.c
> +++ b/arch/riscv/kernel/patch.c
> @@ -42,19 +42,20 @@ static inline bool is_kernel_exittext(uintptr_t addr)
>  static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
>  {
>  	uintptr_t uintaddr = (uintptr_t) addr;
> -	struct page *page;
> +	phys_addr_t phys;
>  
> -	if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr))
> -		page = phys_to_page(__pa_symbol(addr));
> -	else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
> -		page = vmalloc_to_page(addr);
> -	else
> +	if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) {
> +		phys = __pa_symbol(addr);
> +	} else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) {
> +		struct page *page = vmalloc_to_page(addr);
> +
> +		BUG_ON(!page);
> +		phys = page_to_phys(page) + offset_in_page(addr);
> +	} else {
>  		return addr;
> +	}
>  
> -	BUG_ON(!page);
> -
> -	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
> -					 offset_in_page(addr));
> +	return (void *)set_fixmap_offset(fixmap, phys);
>  }
>  
>  static void patch_unmap(int fixmap)
> 
> ---
> base-commit: 1f318b96cc84d7c2ab792fcc0bfd42a7ca890681
> change-id: 20260310-riscv-sparsemem-alternatives-fix-f9ea051b1694
> 
> Best regards,
> -- 
> Vivian "dramforever" Wang
> 

-- 
Sincerely yours,
Mike.