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Message-ID: <CAMj1kXHg-T7Aehe1q8k7HixrwmiAm3tdXNkXGCiW+guctEoShA@mail.gmail.com>
Date: Fri, 16 May 2025 10:50:50 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Jonathan Corbet <corbet@....net>, Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, Jan Kiszka <jan.kiszka@...mens.com>,
Kieran Bingham <kbingham@...nel.org>, Michael Roth <michael.roth@....com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>, Brijesh Singh <brijesh.singh@....com>,
Sandipan Das <sandipan.das@....com>, Juergen Gross <jgross@...e.com>,
Tom Lendacky <thomas.lendacky@....com>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-efi@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 1/3] x86/64/mm: Always use dynamic memory layout
On Fri, 16 May 2025 at 10:15, Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> Dynamic memory layout is used by KASLR and 5-level paging.
>
> CONFIG_X86_5LEVEL is going to be removed, making 5-level paging support
> unconditional which requires unconditional support of dynamic memory
> layout.
>
> Remove CONFIG_DYNAMIC_MEMORY_LAYOUT.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
> ---
> arch/x86/Kconfig | 8 --------
> arch/x86/include/asm/page_64_types.h | 4 ----
> arch/x86/include/asm/pgtable_64_types.h | 6 ------
> arch/x86/kernel/head64.c | 2 --
> scripts/gdb/linux/pgtable.py | 4 +---
> 5 files changed, 1 insertion(+), 23 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 891a69b308cb..d3c2da3b2f0b 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1467,7 +1467,6 @@ config X86_PAE
> config X86_5LEVEL
> bool "Enable 5-level page tables support"
> default y
> - select DYNAMIC_MEMORY_LAYOUT
> select SPARSEMEM_VMEMMAP
> depends on X86_64
> help
> @@ -2167,17 +2166,10 @@ config PHYSICAL_ALIGN
>
> Don't change this unless you know what you are doing.
>
> -config DYNAMIC_MEMORY_LAYOUT
> - bool
> - help
> - This option makes base addresses of vmalloc and vmemmap as well as
> - __PAGE_OFFSET movable during boot.
> -
> config RANDOMIZE_MEMORY
> bool "Randomize the kernel memory sections"
> depends on X86_64
> depends on RANDOMIZE_BASE
> - select DYNAMIC_MEMORY_LAYOUT
> default RANDOMIZE_BASE
> help
> Randomizes the base virtual address of kernel memory sections
> diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
> index 1faa8f88850a..6b8c8169c71d 100644
> --- a/arch/x86/include/asm/page_64_types.h
> +++ b/arch/x86/include/asm/page_64_types.h
> @@ -41,11 +41,7 @@
> #define __PAGE_OFFSET_BASE_L5 _AC(0xff11000000000000, UL)
> #define __PAGE_OFFSET_BASE_L4 _AC(0xffff888000000000, UL)
>
> -#ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
> #define __PAGE_OFFSET page_offset_base
> -#else
> -#define __PAGE_OFFSET __PAGE_OFFSET_BASE_L4
> -#endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */
>
> #define __START_KERNEL_map _AC(0xffffffff80000000, UL)
>
> diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
> index e83721db18c9..eee06f77b245 100644
> --- a/arch/x86/include/asm/pgtable_64_types.h
> +++ b/arch/x86/include/asm/pgtable_64_types.h
> @@ -128,15 +128,9 @@ extern unsigned int ptrs_per_p4d;
> #define __VMEMMAP_BASE_L4 0xffffea0000000000UL
> #define __VMEMMAP_BASE_L5 0xffd4000000000000UL
>
> -#ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
> # define VMALLOC_START vmalloc_base
> # define VMALLOC_SIZE_TB (pgtable_l5_enabled() ? VMALLOC_SIZE_TB_L5 : VMALLOC_SIZE_TB_L4)
> # define VMEMMAP_START vmemmap_base
> -#else
> -# define VMALLOC_START __VMALLOC_BASE_L4
> -# define VMALLOC_SIZE_TB VMALLOC_SIZE_TB_L4
> -# define VMEMMAP_START __VMEMMAP_BASE_L4
> -#endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */
>
> #ifdef CONFIG_RANDOMIZE_MEMORY
> # define DIRECT_MAP_PHYSMEM_END direct_map_physmem_end
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 14f7dda20954..9f617be64fa9 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -59,14 +59,12 @@ unsigned int ptrs_per_p4d __ro_after_init = 1;
> EXPORT_SYMBOL(ptrs_per_p4d);
> #endif
>
> -#ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
> unsigned long page_offset_base __ro_after_init = __PAGE_OFFSET_BASE_L4;
> EXPORT_SYMBOL(page_offset_base);
> unsigned long vmalloc_base __ro_after_init = __VMALLOC_BASE_L4;
> EXPORT_SYMBOL(vmalloc_base);
> unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4;
> EXPORT_SYMBOL(vmemmap_base);
> -#endif
>
> /* Wipe all early page tables except for the kernel symbol map */
> static void __init reset_early_page_tables(void)
> diff --git a/scripts/gdb/linux/pgtable.py b/scripts/gdb/linux/pgtable.py
> index 30d837f3dfae..09aac2421fb8 100644
> --- a/scripts/gdb/linux/pgtable.py
> +++ b/scripts/gdb/linux/pgtable.py
> @@ -29,11 +29,9 @@ def page_mask(level=1):
> raise Exception(f'Unknown page level: {level}')
>
>
> -#page_offset_base in case CONFIG_DYNAMIC_MEMORY_LAYOUT is disabled
> -POB_NO_DYNAMIC_MEM_LAYOUT = '0xffff888000000000'
> def _page_offset_base():
> pob_symbol = gdb.lookup_global_symbol('page_offset_base')
> - pob = pob_symbol.name if pob_symbol else POB_NO_DYNAMIC_MEM_LAYOUT
> + pob = pob_symbol.name
> return gdb.parse_and_eval(pob)
>
>
> --
> 2.47.2
>
>
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