+ Albert Ou, Alexander Gordeev, Brian Cain, Guo Ren, Heiko Carstens, Michael Ellerman, Michal Simek, Palmer Dabbelt, Paul Walmsley, Vasily Gorbik, Vineet Gupta. This was a rather tricky series to get the recipients correct for and my script did not realize that "supporter" was a pseudonym for "maintainer" so you were missed off the original post. Appologies! More context in cover letter: https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ On 14/10/2024 11:58, Ryan Roberts wrote: > arm64 can support multiple base page sizes. Instead of selecting a page > size at compile time, as is done today, we will make it possible to > select the desired page size on the command line. > > In this case PAGE_SHIFT and it's derivatives, PAGE_SIZE and PAGE_MASK > (as well as a number of other macros related to or derived from > PAGE_SHIFT, but I'm not worrying about those yet), are no longer > compile-time constants. So the code base needs to cope with that. > > As a first step, introduce MIN and MAX variants of these macros, which > express the range of possible page sizes. These are always compile-time > constants and can be used in many places where PAGE_[SHIFT|SIZE|MASK] > were previously used where a compile-time constant is required. > (Subsequent patches will do that conversion work). When the arch/build > doesn't support boot-time page size selection, the MIN and MAX variants > are equal and everything resolves as it did previously. > > Additionally, introduce DEFINE_GLOBAL_PAGE_SIZE_VAR[_CONST]() which wrap > global variable defintions so that for boot-time page size selection > builds, the variable being wrapped is initialized at boot-time, instead > of compile-time. This is done by defining a function to do the > assignment, which has the "constructor" attribute. Constructor is > preferred over initcall, because when compiling a module, the module is > limited to a single initcall but constructors are unlimited. For > built-in code, constructors are now called earlier to guarrantee that > the variables are initialized by the time they are used. Any arch that > wants to enable boot-time page size selection will need to select > CONFIG_CONSTRUCTORS. > > These new macros need to be available anywhere PAGE_SHIFT and friends > are available. Those are defined via asm/page.h (although some arches > have a sub-include that defines them). Unfortunately there is no > reliable asm-generic header we can easily piggy-back on, so let's define > a new one, pgtable-geometry.h, which we include near where each arch > defines PAGE_SHIFT. Ugh. > > ------- > > Most of the problems that need to be solved over the next few patches > fall into these broad categories, which are all solved with the help of > these new macros: > > 1. Assignment of values derived from PAGE_SIZE in global variables > > For boot-time page size builds, we must defer the initialization of > these variables until boot-time, when the page size is known. See > DEFINE_GLOBAL_PAGE_SIZE_VAR[_CONST]() as described above. > > 2. Define static storage in units related to PAGE_SIZE > > This static storage will be defined according to PAGE_SIZE_MAX. > > 3. Define size of struct so that it is related to PAGE_SIZE > > The struct often contains an array that is sized to fill the page. In > this case, use a flexible array with dynamic allocation. In other > cases, the struct fits exactly over a page, which is a header (e.g. > swap file header). In this case, remove the padding, and manually > determine the struct pointer within the page. > > 4. BUILD_BUG_ON() with values derived from PAGE_SIZE > > In most cases, we can change these to compare againt the appropriate > limit (either MIN or MAX). In other cases, we must change these to > run-time BUG_ON(). > > 5. Ensure page alignment of static data structures > > Align instead to PAGE_SIZE_MAX. > > 6. #ifdeffery based on PAGE_SIZE > > Often these can be changed to c code constructs. e.g. a macro that > returns a different value depending on page size can be changed to use > the ternary operator and the compiler will dead code strip it for the > compile-time constant case and runtime evaluate it for the non-const > case. Or #if/#else/#endif within a function can be converted to c > if/else blocks, which are also dead code stripped for the const case. > Sometimes we can change the c-preprocessor logic to use the > appropriate MIN/MAX limit. > > Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> > --- > > ***NOTE*** > Any confused maintainers may want to read the cover note here for context: > https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ > > arch/alpha/include/asm/page.h | 1 + > arch/arc/include/asm/page.h | 1 + > arch/arm/include/asm/page.h | 1 + > arch/arm64/include/asm/page-def.h | 2 + > arch/csky/include/asm/page.h | 3 ++ > arch/hexagon/include/asm/page.h | 2 + > arch/loongarch/include/asm/page.h | 2 + > arch/m68k/include/asm/page.h | 1 + > arch/microblaze/include/asm/page.h | 1 + > arch/mips/include/asm/page.h | 1 + > arch/nios2/include/asm/page.h | 2 + > arch/openrisc/include/asm/page.h | 1 + > arch/parisc/include/asm/page.h | 1 + > arch/powerpc/include/asm/page.h | 2 + > arch/riscv/include/asm/page.h | 1 + > arch/s390/include/asm/page.h | 1 + > arch/sh/include/asm/page.h | 1 + > arch/sparc/include/asm/page.h | 3 ++ > arch/um/include/asm/page.h | 2 + > arch/x86/include/asm/page_types.h | 2 + > arch/xtensa/include/asm/page.h | 1 + > include/asm-generic/pgtable-geometry.h | 71 ++++++++++++++++++++++++++ > init/main.c | 5 +- > 23 files changed, 107 insertions(+), 1 deletion(-) > create mode 100644 include/asm-generic/pgtable-geometry.h > > diff --git a/arch/alpha/include/asm/page.h b/arch/alpha/include/asm/page.h > index 70419e6be1a35..d0096fb5521b8 100644 > --- a/arch/alpha/include/asm/page.h > +++ b/arch/alpha/include/asm/page.h > @@ -88,5 +88,6 @@ typedef struct page *pgtable_t; > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* _ALPHA_PAGE_H */ > diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h > index def0dfb95b436..8d56549db7a33 100644 > --- a/arch/arc/include/asm/page.h > +++ b/arch/arc/include/asm/page.h > @@ -6,6 +6,7 @@ > #define __ASM_ARC_PAGE_H > > #include <uapi/asm/page.h> > +#include <asm-generic/pgtable-geometry.h> > > #ifdef CONFIG_ARC_HAS_PAE40 > > diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h > index 62af9f7f9e963..417aa8533c718 100644 > --- a/arch/arm/include/asm/page.h > +++ b/arch/arm/include/asm/page.h > @@ -191,5 +191,6 @@ extern int pfn_valid(unsigned long); > > #include <asm-generic/getorder.h> > #include <asm-generic/memory_model.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif > diff --git a/arch/arm64/include/asm/page-def.h b/arch/arm64/include/asm/page-def.h > index 792e9fe881dcf..d69971cf49cd2 100644 > --- a/arch/arm64/include/asm/page-def.h > +++ b/arch/arm64/include/asm/page-def.h > @@ -15,4 +15,6 @@ > #define PAGE_SIZE (_AC(1, UL) << PAGE_SHIFT) > #define PAGE_MASK (~(PAGE_SIZE-1)) > > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* __ASM_PAGE_DEF_H */ > diff --git a/arch/csky/include/asm/page.h b/arch/csky/include/asm/page.h > index 0ca6c408c07f2..95173d57adc8b 100644 > --- a/arch/csky/include/asm/page.h > +++ b/arch/csky/include/asm/page.h > @@ -92,4 +92,7 @@ static inline unsigned long virt_to_pfn(const void *kaddr) > #include <asm-generic/getorder.h> > > #endif /* !__ASSEMBLY__ */ > + > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* __ASM_CSKY_PAGE_H */ > diff --git a/arch/hexagon/include/asm/page.h b/arch/hexagon/include/asm/page.h > index 8a6af57274c2d..ba7ad5231695f 100644 > --- a/arch/hexagon/include/asm/page.h > +++ b/arch/hexagon/include/asm/page.h > @@ -139,4 +139,6 @@ static inline unsigned long virt_to_pfn(const void *kaddr) > #endif /* ifdef __ASSEMBLY__ */ > #endif /* ifdef __KERNEL__ */ > > +#include <asm-generic/pgtable-geometry.h> > + > #endif > diff --git a/arch/loongarch/include/asm/page.h b/arch/loongarch/include/asm/page.h > index e85df33f11c77..9862e8fb047a6 100644 > --- a/arch/loongarch/include/asm/page.h > +++ b/arch/loongarch/include/asm/page.h > @@ -123,4 +123,6 @@ extern int __virt_addr_valid(volatile void *kaddr); > > #endif /* !__ASSEMBLY__ */ > > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* _ASM_PAGE_H */ > diff --git a/arch/m68k/include/asm/page.h b/arch/m68k/include/asm/page.h > index 8cfb84b499751..4df4681b02194 100644 > --- a/arch/m68k/include/asm/page.h > +++ b/arch/m68k/include/asm/page.h > @@ -60,5 +60,6 @@ extern unsigned long _ramend; > > #include <asm-generic/getorder.h> > #include <asm-generic/memory_model.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* _M68K_PAGE_H */ > diff --git a/arch/microblaze/include/asm/page.h b/arch/microblaze/include/asm/page.h > index 8810f4f1c3b02..abc23c3d743bd 100644 > --- a/arch/microblaze/include/asm/page.h > +++ b/arch/microblaze/include/asm/page.h > @@ -142,5 +142,6 @@ static inline const void *pfn_to_virt(unsigned long pfn) > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* _ASM_MICROBLAZE_PAGE_H */ > diff --git a/arch/mips/include/asm/page.h b/arch/mips/include/asm/page.h > index 4609cb0326cf3..3d91021538f02 100644 > --- a/arch/mips/include/asm/page.h > +++ b/arch/mips/include/asm/page.h > @@ -227,5 +227,6 @@ static inline unsigned long kaslr_offset(void) > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* _ASM_PAGE_H */ > diff --git a/arch/nios2/include/asm/page.h b/arch/nios2/include/asm/page.h > index 0722f88e63cc7..2e5f93beb42b7 100644 > --- a/arch/nios2/include/asm/page.h > +++ b/arch/nios2/include/asm/page.h > @@ -97,4 +97,6 @@ extern struct page *mem_map; > > #endif /* !__ASSEMBLY__ */ > > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* _ASM_NIOS2_PAGE_H */ > diff --git a/arch/openrisc/include/asm/page.h b/arch/openrisc/include/asm/page.h > index 1d5913f67c312..a0da2a9842241 100644 > --- a/arch/openrisc/include/asm/page.h > +++ b/arch/openrisc/include/asm/page.h > @@ -88,5 +88,6 @@ static inline unsigned long virt_to_pfn(const void *kaddr) > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* __ASM_OPENRISC_PAGE_H */ > diff --git a/arch/parisc/include/asm/page.h b/arch/parisc/include/asm/page.h > index 4bea2e95798f0..2a75496237c09 100644 > --- a/arch/parisc/include/asm/page.h > +++ b/arch/parisc/include/asm/page.h > @@ -173,6 +173,7 @@ extern int npmem_ranges; > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > #include <asm/pdc.h> > > #define PAGE0 ((struct zeropage *)absolute_pointer(__PAGE_OFFSET)) > diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h > index 83d0a4fc5f755..4601c115b6485 100644 > --- a/arch/powerpc/include/asm/page.h > +++ b/arch/powerpc/include/asm/page.h > @@ -300,4 +300,6 @@ static inline unsigned long kaslr_offset(void) > #include <asm-generic/memory_model.h> > #endif /* __ASSEMBLY__ */ > > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* _ASM_POWERPC_PAGE_H */ > diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h > index 7ede2111c5917..e5af7579e45bf 100644 > --- a/arch/riscv/include/asm/page.h > +++ b/arch/riscv/include/asm/page.h > @@ -204,5 +204,6 @@ static __always_inline void *pfn_to_kaddr(unsigned long pfn) > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* _ASM_RISCV_PAGE_H */ > diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h > index 16e4caa931f1f..42157e7690a77 100644 > --- a/arch/s390/include/asm/page.h > +++ b/arch/s390/include/asm/page.h > @@ -275,6 +275,7 @@ static inline unsigned long virt_to_pfn(const void *kaddr) > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #define AMODE31_SIZE (3 * PAGE_SIZE) > > diff --git a/arch/sh/include/asm/page.h b/arch/sh/include/asm/page.h > index f780b467e75d7..09533d46ef033 100644 > --- a/arch/sh/include/asm/page.h > +++ b/arch/sh/include/asm/page.h > @@ -162,5 +162,6 @@ typedef struct page *pgtable_t; > > #include <asm-generic/memory_model.h> > #include <asm-generic/getorder.h> > +#include <asm-generic/pgtable-geometry.h> > > #endif /* __ASM_SH_PAGE_H */ > diff --git a/arch/sparc/include/asm/page.h b/arch/sparc/include/asm/page.h > index 5e44cdf2a8f2b..4327fe2bfa010 100644 > --- a/arch/sparc/include/asm/page.h > +++ b/arch/sparc/include/asm/page.h > @@ -9,4 +9,7 @@ > #else > #include <asm/page_32.h> > #endif > + > +#include <asm-generic/pgtable-geometry.h> > + > #endif > diff --git a/arch/um/include/asm/page.h b/arch/um/include/asm/page.h > index 9ef9a8aedfa66..f26011808f514 100644 > --- a/arch/um/include/asm/page.h > +++ b/arch/um/include/asm/page.h > @@ -119,4 +119,6 @@ extern unsigned long uml_physmem; > #define __HAVE_ARCH_GATE_AREA 1 > #endif > > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* __UM_PAGE_H */ > diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h > index 52f1b4ff0cc16..6d2381342047f 100644 > --- a/arch/x86/include/asm/page_types.h > +++ b/arch/x86/include/asm/page_types.h > @@ -71,4 +71,6 @@ extern void initmem_init(void); > > #endif /* !__ASSEMBLY__ */ > > +#include <asm-generic/pgtable-geometry.h> > + > #endif /* _ASM_X86_PAGE_DEFS_H */ > diff --git a/arch/xtensa/include/asm/page.h b/arch/xtensa/include/asm/page.h > index 4db56ef052d22..86952cb32af23 100644 > --- a/arch/xtensa/include/asm/page.h > +++ b/arch/xtensa/include/asm/page.h > @@ -200,4 +200,5 @@ static inline unsigned long ___pa(unsigned long va) > #endif /* __ASSEMBLY__ */ > > #include <asm-generic/memory_model.h> > +#include <asm-generic/pgtable-geometry.h> > #endif /* _XTENSA_PAGE_H */ > diff --git a/include/asm-generic/pgtable-geometry.h b/include/asm-generic/pgtable-geometry.h > new file mode 100644 > index 0000000000000..358e729a6ac37 > --- /dev/null > +++ b/include/asm-generic/pgtable-geometry.h > @@ -0,0 +1,71 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef ASM_GENERIC_PGTABLE_GEOMETRY_H > +#define ASM_GENERIC_PGTABLE_GEOMETRY_H > + > +#if defined(PAGE_SHIFT_MAX) && defined(PAGE_SIZE_MAX) && defined(PAGE_MASK_MAX) && \ > + defined(PAGE_SHIFT_MIN) && defined(PAGE_SIZE_MIN) && defined(PAGE_MASK_MIN) > +/* Arch supports boot-time page size selection. */ > +#elif defined(PAGE_SHIFT_MAX) || defined(PAGE_SIZE_MAX) || defined(PAGE_MASK_MAX) || \ > + defined(PAGE_SHIFT_MIN) || defined(PAGE_SIZE_MIN) || defined(PAGE_MASK_MIN) > +#error Arch must define all or none of the boot-time page size macros > +#else > +/* Arch does not support boot-time page size selection. */ > +#define PAGE_SHIFT_MIN PAGE_SHIFT > +#define PAGE_SIZE_MIN PAGE_SIZE > +#define PAGE_MASK_MIN PAGE_MASK > +#define PAGE_SHIFT_MAX PAGE_SHIFT > +#define PAGE_SIZE_MAX PAGE_SIZE > +#define PAGE_MASK_MAX PAGE_MASK > +#endif > + > +/* > + * Define a global variable (scalar or struct), whose value is derived from > + * PAGE_SIZE and friends. When PAGE_SIZE is a compile-time constant, the global > + * variable is simply defined with the static value. When PAGE_SIZE is > + * determined at boot-time, a pure initcall is registered and run during boot to > + * initialize the variable. > + * > + * @type: Unqualified type. Do not include "const"; implied by macro variant. > + * @name: Variable name. > + * @...: Initialization value. May be scalar or initializer. > + * > + * "static" is declared by placing "static" before the macro. > + * > + * Example: > + * > + * struct my_struct { > + * int a; > + * char b; > + * }; > + * > + * static DEFINE_GLOBAL_PAGE_SIZE_VAR(struct my_struct, my_variable, { > + * .a = 10, > + * .b = 'e', > + * }); > + */ > +#if PAGE_SIZE_MIN != PAGE_SIZE_MAX > +#define __DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, attrib, ...) \ > + type name attrib; \ > + static int __init __attribute__((constructor)) __##name##_init(void) \ > + { \ > + name = (type)__VA_ARGS__; \ > + return 0; \ > + } > + > +#define DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, ...) \ > + __DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, , __VA_ARGS__) > + > +#define DEFINE_GLOBAL_PAGE_SIZE_VAR_CONST(type, name, ...) \ > + __DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, __ro_after_init, __VA_ARGS__) > +#else /* PAGE_SIZE_MIN == PAGE_SIZE_MAX */ > +#define __DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, attrib, ...) \ > + type name attrib = __VA_ARGS__; \ > + > +#define DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, ...) \ > + __DEFINE_GLOBAL_PAGE_SIZE_VAR(type, name, , __VA_ARGS__) > + > +#define DEFINE_GLOBAL_PAGE_SIZE_VAR_CONST(type, name, ...) \ > + __DEFINE_GLOBAL_PAGE_SIZE_VAR(const type, name, , __VA_ARGS__) > +#endif > + > +#endif /* ASM_GENERIC_PGTABLE_GEOMETRY_H */ > diff --git a/init/main.c b/init/main.c > index 206acdde51f5a..ba1515eb20b9d 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -899,6 +899,8 @@ static void __init early_numa_node_init(void) > #endif > } > > +static __init void do_ctors(void); > + > asmlinkage __visible __init __no_sanitize_address __noreturn __no_stack_protector > void start_kernel(void) > { > @@ -910,6 +912,8 @@ void start_kernel(void) > debug_objects_early_init(); > init_vmlinux_build_id(); > > + do_ctors(); > + > cgroup_init_early(); > > local_irq_disable(); > @@ -1360,7 +1364,6 @@ static void __init do_basic_setup(void) > cpuset_init_smp(); > driver_init(); > init_irq_proc(); > - do_ctors(); > do_initcalls(); > } >
