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Message-ID: <CAJFTR8RJYdT6CQ=FgBkM3jUj=PnYnuyi3+bO3=NPeH6xJ6TTaw@mail.gmail.com>
Date: Sun, 27 Oct 2024 16:25:30 -0400
From: Jesse T <mr.bossman075@...il.com>
To: Samuel Holland <samuel.holland@...ive.com>
Cc: Palmer Dabbelt <palmer@...belt.com>, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, Andrew Morton <akpm@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>, Alexandre Ghiti <alexghiti@...osinc.com>
Subject: Re: [PATCH 6/6] riscv: Remove CONFIG_PAGE_OFFSET
On Sat, Oct 26, 2024 at 1:16 PM Samuel Holland
<samuel.holland@...ive.com> wrote:
>
> The current definition of CONFIG_PAGE_OFFSET is problematic for a couple
> of reasons:
> 1) The value is misleading for normal 64-bit kernels, where it is
> overridden at runtime if Sv48 or Sv39 is chosen. This is especially
> the case for XIP kernels, which always use Sv39.
> 2) The option is not user-visible, but for NOMMU kernels it must be a
> valid RAM address, and for !RELOCATABLE it must additionally be the
> exact address where the kernel is loaded.
>
> Fix both of these by removing the option.
> 1) For MMU kernels, drop the indirection through Kconfig. Additionally,
> for XIP, drop the indirection through kernel_map.
> 2) For NOMMU kernels, use the user-visible physical RAM base if
> provided. Otherwise, force the kernel to be relocatable.
>
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
Reviewed-by: Jesse Taube <mr.bossman075@...il.com>
> ---
>
> arch/riscv/Kconfig | 8 +-------
> arch/riscv/include/asm/page.h | 15 ++++++++-------
> arch/riscv/include/asm/pgtable.h | 2 +-
> arch/riscv/mm/init.c | 8 ++------
> 4 files changed, 12 insertions(+), 21 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 33aa79d84021..297ccbf4b5ce 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -195,6 +195,7 @@ config RISCV
> select PCI_DOMAINS_GENERIC if PCI
> select PCI_ECAM if (ACPI && PCI)
> select PCI_MSI if PCI
> + select RELOCATABLE if !MMU && !PHYS_RAM_BASE_FIXED
> select RISCV_ALTERNATIVE if !XIP_KERNEL
> select RISCV_APLIC
> select RISCV_IMSIC
> @@ -282,13 +283,6 @@ config MMU
> Select if you want MMU-based virtualised addressing space
> support by paged memory management. If unsure, say 'Y'.
>
> -config PAGE_OFFSET
> - hex
> - default 0x80000000 if !MMU && RISCV_M_MODE
> - default 0x80200000 if !MMU
Should the default values above now be moved to CONFIG_PHYS_RAM_BASE?
> - default 0xc0000000 if 32BIT
> - default 0xff60000000000000 if 64BIT
> -
> config KASAN_SHADOW_OFFSET
> hex
> depends on KASAN_GENERIC
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 24d1ac052609..d1acd1efe0dc 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -28,15 +28,16 @@
> */
> #ifdef CONFIG_MMU
> #ifdef CONFIG_64BIT
> -#define PAGE_OFFSET kernel_map.page_offset
> -/*
> - * By default, CONFIG_PAGE_OFFSET value corresponds to SV57 address space so
> - * define the PAGE_OFFSET value for SV48 and SV39.
> - */
> +#define PAGE_OFFSET_L5 _AC(0xff60000000000000, UL)
> #define PAGE_OFFSET_L4 _AC(0xffffaf8000000000, UL)
> #define PAGE_OFFSET_L3 _AC(0xffffffd600000000, UL)
> +#ifdef CONFIG_XIP_KERNEL
> +#define PAGE_OFFSET PAGE_OFFSET_L3
> #else
> -#define PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL)
> +#define PAGE_OFFSET kernel_map.page_offset
> +#endif /* CONFIG_XIP_KERNEL */
> +#else
> +#define PAGE_OFFSET _AC(0xc0000000, UL)
> #endif /* CONFIG_64BIT */
> #else
> #define PAGE_OFFSET ((unsigned long)phys_ram_base)
> @@ -100,7 +101,6 @@ typedef struct page *pgtable_t;
> #define ARCH_PFN_OFFSET (PFN_DOWN((unsigned long)phys_ram_base))
>
> struct kernel_mapping {
> - unsigned long page_offset;
> unsigned long virt_addr;
> unsigned long virt_offset;
> uintptr_t phys_addr;
> @@ -114,6 +114,7 @@ struct kernel_mapping {
> uintptr_t xiprom;
> uintptr_t xiprom_sz;
> #else
> + unsigned long page_offset;
> unsigned long va_kernel_pa_offset;
> #endif
> };
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index d0190ee9b2e4..b8125c3aa85d 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -15,7 +15,7 @@
> #ifdef CONFIG_RELOCATABLE
> #define KERNEL_LINK_ADDR UL(0)
> #else
> -#define KERNEL_LINK_ADDR _AC(CONFIG_PAGE_OFFSET, UL)
> +#define KERNEL_LINK_ADDR _AC(CONFIG_PHYS_RAM_BASE, UL)
> #endif
> #define KERN_VIRT_SIZE (UL(-1))
> #else
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 0aad925848a4..a1a185e6faf0 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -843,6 +843,8 @@ static __init void set_satp_mode(uintptr_t dtb_pa)
> uintptr_t set_satp_mode_pmd = ((unsigned long)set_satp_mode) & PMD_MASK;
> u64 satp_mode_cmdline = __pi_set_satp_mode_from_cmdline(dtb_pa);
>
> + kernel_map.page_offset = PAGE_OFFSET_L5;
> +
> if (satp_mode_cmdline == SATP_MODE_57) {
> disable_pgtable_l5();
> } else if (satp_mode_cmdline == SATP_MODE_48) {
> @@ -1090,11 +1092,6 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> kernel_map.virt_addr = KERNEL_LINK_ADDR + kernel_map.virt_offset;
>
> #ifdef CONFIG_XIP_KERNEL
> -#ifdef CONFIG_64BIT
> - kernel_map.page_offset = PAGE_OFFSET_L3;
> -#else
> - kernel_map.page_offset = _AC(CONFIG_PAGE_OFFSET, UL);
> -#endif
> kernel_map.xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
> kernel_map.xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
>
> @@ -1106,7 +1103,6 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> kernel_map.va_kernel_xip_data_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr
> + (uintptr_t)&_sdata - (uintptr_t)&_start;
> #else
> - kernel_map.page_offset = _AC(CONFIG_PAGE_OFFSET, UL);
> kernel_map.phys_addr = (uintptr_t)(&_start);
> kernel_map.size = (uintptr_t)(&_end) - kernel_map.phys_addr;
> kernel_map.va_kernel_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr;
> --
> 2.45.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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