Re: [RFC PATCH v1 57/57] arm64: Enable boot-time page size selection

Ryan Roberts
2024-10-16T08:17:22Z

On 15/10/2024 18:52, Michael Kelley wrote:
> From: Ryan Roberts <ryan.roberts@arm.com> Sent: Monday, October 14, 2024 3:59 AM
>>
>> Introduce a new Kconfig, ARM64_BOOT_TIME_PAGE_SIZE, which can be
>> selected instead of a page size. When selected, the resulting kernel's
>> page size can be configured at boot via the command line.
>>
>> For now, boot-time page size kernels are limited to 48-bit VA, since
>> more work is required to support LPA2. Additionally MMAP_RND_BITS and
>> SECTION_SIZE_BITS are configured for the worst case (64K pages). Future
>> work could be implemented to be able to configure these at boot time for
>> optimial page size-specific values.
>>
>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
>> ---
>>
>> ***NOTE***
>> Any confused maintainers may want to read the cover note here for context:
>> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
>>
>> arch/arm64/Kconfig | 26 ++++++++++---
>> arch/arm64/include/asm/kvm_hyp.h | 11 ++++++
>> arch/arm64/include/asm/pgtable-geometry.h | 22 ++++++++++-
>> arch/arm64/include/asm/pgtable-hwdef.h | 6 +--
>> arch/arm64/include/asm/pgtable.h | 10 ++++-
>> arch/arm64/include/asm/sparsemem.h | 4 ++
>> arch/arm64/kernel/image-vars.h | 11 ++++++
>> arch/arm64/kernel/image.h | 4 ++
>> arch/arm64/kernel/pi/map_kernel.c | 45 ++++++++++++++++++++++
>> arch/arm64/kvm/arm.c | 10 +++++
>> arch/arm64/kvm/hyp/nvhe/Makefile | 1 +
>> arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c | 16 ++++++++
>> arch/arm64/mm/Makefile | 1 +
>> arch/arm64/mm/pgd.c | 10 +++--
>> arch/arm64/mm/pgtable-geometry.c | 24 ++++++++++++
>> drivers/firmware/efi/libstub/arm64.c | 3 +-
>> 16 files changed, 187 insertions(+), 17 deletions(-)
>> create mode 100644 arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c
>> create mode 100644 arch/arm64/mm/pgtable-geometry.c
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index a2f8ff354ca67..573d308741169 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -121,6 +121,7 @@ config ARM64
>> select BUILDTIME_TABLE_SORT
>> select CLONE_BACKWARDS
>> select COMMON_CLK
>> + select CONSTRUCTORS if ARM64_BOOT_TIME_PAGE_SIZE
>> select CPU_PM if (SUSPEND || CPU_IDLE)
>> select CPUMASK_OFFSTACK if NR_CPUS > 256
>> select CRC32
>> @@ -284,18 +285,20 @@ config MMU
>>
>> config ARM64_CONT_PTE_SHIFT
>> int
>> + depends on !ARM64_BOOT_TIME_PAGE_SIZE
>> default 5 if PAGE_SIZE_64KB
>> default 7 if PAGE_SIZE_16KB
>> default 4
>>
>> config ARM64_CONT_PMD_SHIFT
>> int
>> + depends on !ARM64_BOOT_TIME_PAGE_SIZE
>> default 5 if PAGE_SIZE_64KB
>> default 5 if PAGE_SIZE_16KB
>> default 4
>>
>> config ARCH_MMAP_RND_BITS_MIN
>> - default 14 if PAGE_SIZE_64KB
>> + default 14 if ARM64_64K_PAGES || ARM64_BOOT_TIME_PAGE_SIZE
>> default 16 if PAGE_SIZE_16KB
>> default 18
>>
>> @@ -306,15 +309,15 @@ config ARCH_MMAP_RND_BITS_MAX
>> default 24 if ARM64_VA_BITS=39
>> default 27 if ARM64_VA_BITS=42
>> default 30 if ARM64_VA_BITS=47
>> - default 29 if ARM64_VA_BITS=48 && ARM64_64K_PAGES
>> + default 29 if ARM64_VA_BITS=48 && (ARM64_64K_PAGES ||
>> ARM64_BOOT_TIME_PAGE_SIZE)
>> default 31 if ARM64_VA_BITS=48 && ARM64_16K_PAGES
>> default 33 if ARM64_VA_BITS=48
>> - default 14 if ARM64_64K_PAGES
>> + default 14 if ARM64_64K_PAGES || ARM64_BOOT_TIME_PAGE_SIZE
>> default 16 if ARM64_16K_PAGES
>> default 18
>>
>> config ARCH_MMAP_RND_COMPAT_BITS_MIN
>> - default 7 if ARM64_64K_PAGES
>> + default 7 if ARM64_64K_PAGES || ARM64_BOOT_TIME_PAGE_SIZE
>> default 9 if ARM64_16K_PAGES
>> default 11
>>
>> @@ -362,6 +365,7 @@ config FIX_EARLYCON_MEM
>>
>> config PGTABLE_LEVELS
>> int
>> + default 4 if ARM64_BOOT_TIME_PAGE_SIZE # Advertise max supported levels
>> default 2 if ARM64_16K_PAGES && ARM64_VA_BITS_36
>> default 2 if ARM64_64K_PAGES && ARM64_VA_BITS_42
>> default 3 if ARM64_64K_PAGES && (ARM64_VA_BITS_48 ||
>> ARM64_VA_BITS_52)
>> @@ -1316,6 +1320,14 @@ config ARM64_64K_PAGES
>> look-up. AArch32 emulation requires applications compiled
>> with 64K aligned segments.
>>
>> +config ARM64_BOOT_TIME_PAGE_SIZE
>> + bool "Boot-time selection"
>> + select HAVE_PAGE_SIZE_64KB # Advertise largest page size to core
>> + help
>> + Select desired page size (4KB, 16KB or 64KB) at boot-time via the
>> + kernel command line option "arm64.pagesize=4k", "arm64.pagesize=16k"
>> + or "arm64.pagesize=64k".
>> +
>> endchoice
>>
>> choice
>> @@ -1348,6 +1360,7 @@ config ARM64_VA_BITS_48
>> config ARM64_VA_BITS_52
>> bool "52-bit"
>> depends on ARM64_PAN || !ARM64_SW_TTBR0_PAN
>> + depends on !ARM64_BOOT_TIME_PAGE_SIZE
>> help
>> Enable 52-bit virtual addressing for userspace when explicitly
>> requested via a hint to mmap(). The kernel will also use 52-bit
>> @@ -1588,9 +1601,10 @@ config XEN
>> # 4K | 27 | 12 | 15 | 10 |
>> # 16K | 27 | 14 | 13 | 11 |
>> # 64K | 29 | 16 | 13 | 13 |
>> +# BOOT| 29 | 16 (max) | 13 | 13 |
>> config ARCH_FORCE_MAX_ORDER
>> int
>> - default "13" if ARM64_64K_PAGES
>> + default "13" if ARM64_64K_PAGES || ARM64_BOOT_TIME_PAGE_SIZE
>> default "11" if ARM64_16K_PAGES
>> default "10"
>> help
>> @@ -1663,7 +1677,7 @@ config ARM64_TAGGED_ADDR_ABI
>>
>> menuconfig COMPAT
>> bool "Kernel support for 32-bit EL0"
>> - depends on ARM64_4K_PAGES || EXPERT
>> + depends on ARM64_4K_PAGES || ARM64_BOOT_TIME_PAGE_SIZE || EXPERT
>> select HAVE_UID16
>> select OLD_SIGSUSPEND3
>> select COMPAT_OLD_SIGACTION
>> diff --git a/arch/arm64/include/asm/kvm_hyp.h
>> b/arch/arm64/include/asm/kvm_hyp.h
>> index c838309e4ec47..9397a14642afa 100644
>> --- a/arch/arm64/include/asm/kvm_hyp.h
>> +++ b/arch/arm64/include/asm/kvm_hyp.h
>> @@ -145,4 +145,15 @@ extern unsigned long kvm_nvhe_sym(__icache_flags);
>> extern unsigned int kvm_nvhe_sym(kvm_arm_vmid_bits);
>> extern unsigned int kvm_nvhe_sym(kvm_host_sve_max_vl);
>>
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +extern int kvm_nvhe_sym(ptg_page_shift);
>> +extern int kvm_nvhe_sym(ptg_pmd_shift);
>> +extern int kvm_nvhe_sym(ptg_pud_shift);
>> +extern int kvm_nvhe_sym(ptg_p4d_shift);
>> +extern int kvm_nvhe_sym(ptg_pgdir_shift);
>> +extern int kvm_nvhe_sym(ptg_cont_pte_shift);
>> +extern int kvm_nvhe_sym(ptg_cont_pmd_shift);
>> +extern int kvm_nvhe_sym(ptg_pgtable_levels);
>> +#endif /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> +
>> #endif /* __ARM64_KVM_HYP_H__ */
>> diff --git a/arch/arm64/include/asm/pgtable-geometry.h
>> b/arch/arm64/include/asm/pgtable-geometry.h
>> index 62fe125909c08..18a8c8d499ecc 100644
>> --- a/arch/arm64/include/asm/pgtable-geometry.h
>> +++ b/arch/arm64/include/asm/pgtable-geometry.h
>> @@ -6,16 +6,33 @@
>> #define ARM64_PAGE_SHIFT_16K 14
>> #define ARM64_PAGE_SHIFT_64K 16
>>
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +#define PAGE_SHIFT_MIN ARM64_PAGE_SHIFT_4K
>> +#define PAGE_SHIFT_MAX ARM64_PAGE_SHIFT_64K
>> +#else /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> #define PAGE_SHIFT_MIN CONFIG_PAGE_SHIFT
>> +#define PAGE_SHIFT_MAX CONFIG_PAGE_SHIFT
>> +#endif /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> +
>> #define PAGE_SIZE_MIN (_AC(1, UL) << PAGE_SHIFT_MIN)
>> #define PAGE_MASK_MIN (~(PAGE_SIZE_MIN-1))
>> -
>> -#define PAGE_SHIFT_MAX CONFIG_PAGE_SHIFT
>> #define PAGE_SIZE_MAX (_AC(1, UL) << PAGE_SHIFT_MAX)
>> #define PAGE_MASK_MAX (~(PAGE_SIZE_MAX-1))
>>
>> #include <asm-generic/pgtable-geometry.h>
>>
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +#ifndef __ASSEMBLY__
>> +extern int ptg_page_shift;
>> +extern int ptg_pmd_shift;
>> +extern int ptg_pud_shift;
>> +extern int ptg_p4d_shift;
>> +extern int ptg_pgdir_shift;
>> +extern int ptg_cont_pte_shift;
>> +extern int ptg_cont_pmd_shift;
>> +extern int ptg_pgtable_levels;
>> +#endif /* __ASSEMBLY__ */
>> +#else /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> #define ptg_page_shift CONFIG_PAGE_SHIFT
>> #define ptg_pmd_shift ARM64_HW_PGTABLE_LEVEL_SHIFT(2)
>> #define ptg_pud_shift ARM64_HW_PGTABLE_LEVEL_SHIFT(1)
>> @@ -24,5 +41,6 @@
>> #define ptg_cont_pte_shift (CONFIG_ARM64_CONT_PTE_SHIFT + PAGE_SHIFT)
>> #define ptg_cont_pmd_shift (CONFIG_ARM64_CONT_PMD_SHIFT + PMD_SHIFT)
>> #define ptg_pgtable_levels CONFIG_PGTABLE_LEVELS
>> +#endif /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>>
>> #endif /* ASM_PGTABLE_GEOMETRY_H */
>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h
>> b/arch/arm64/include/asm/pgtable-hwdef.h
>> index ca8bcbc1fe220..da5404617acbf 100644
>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>> @@ -52,7 +52,7 @@
>> #define PMD_SHIFT ptg_pmd_shift
>> #define PMD_SIZE (_AC(1, UL) << PMD_SHIFT)
>> #define PMD_MASK (~(PMD_SIZE-1))
>> -#define PTRS_PER_PMD (1 << (PAGE_SHIFT - 3))
>> +#define PTRS_PER_PMD (ptg_pgtable_levels > 2 ? (1 << (PAGE_SHIFT -
>> 3)) : 1)
>> #define MAX_PTRS_PER_PMD (1 << (PAGE_SHIFT_MAX - 3))
>> #endif
>>
>> @@ -63,7 +63,7 @@
>> #define PUD_SHIFT ptg_pud_shift
>> #define PUD_SIZE (_AC(1, UL) << PUD_SHIFT)
>> #define PUD_MASK (~(PUD_SIZE-1))
>> -#define PTRS_PER_PUD (1 << (PAGE_SHIFT - 3))
>> +#define PTRS_PER_PUD (ptg_pgtable_levels > 3 ? (1 << (PAGE_SHIFT -
>> 3)) : 1)
>> #define MAX_PTRS_PER_PUD (1 << (PAGE_SHIFT_MAX - 3))
>> #endif
>>
>> @@ -71,7 +71,7 @@
>> #define P4D_SHIFT ptg_p4d_shift
>> #define P4D_SIZE (_AC(1, UL) << P4D_SHIFT)
>> #define P4D_MASK (~(P4D_SIZE-1))
>> -#define PTRS_PER_P4D (1 << (PAGE_SHIFT - 3))
>> +#define PTRS_PER_P4D (ptg_pgtable_levels > 4 ? (1 << (PAGE_SHIFT -
>> 3)) : 1)
>> #define MAX_PTRS_PER_P4D (1 << (PAGE_SHIFT_MAX - 3))
>> #endif
>>
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index 8ead41da715b0..ad9f75f5cc29a 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -755,7 +755,7 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
>>
>> static __always_inline bool pgtable_l3_enabled(void)
>> {
>> - return true;
>> + return ptg_pgtable_levels > 2;
>> }
>>
>> static inline bool mm_pmd_folded(const struct mm_struct *mm)
>> @@ -888,6 +888,8 @@ static inline bool pgtable_l3_enabled(void) { return false; }
>>
>> static __always_inline bool pgtable_l4_enabled(void)
>> {
>> + if (IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE))
>> + return ptg_pgtable_levels > 3;
>> if (CONFIG_PGTABLE_LEVELS > 4 || !IS_ENABLED(CONFIG_ARM64_LPA2))
>> return true;
>> if (!alternative_has_cap_likely(ARM64_ALWAYS_BOOT))
>> @@ -935,6 +937,8 @@ static inline phys_addr_t p4d_page_paddr(p4d_t p4d)
>>
>> static inline pud_t *p4d_to_folded_pud(p4d_t *p4dp, unsigned long addr)
>> {
>> + if (IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE))
>> + return (pud_t *)p4dp;
>> return (pud_t *)PTR_ALIGN_DOWN(p4dp, PAGE_SIZE) + pud_index(addr);
>> }
>>
>> @@ -1014,6 +1018,8 @@ static inline bool pgtable_l4_enabled(void) { return false; }
>>
>> static __always_inline bool pgtable_l5_enabled(void)
>> {
>> + if (IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE))
>> + return ptg_pgtable_levels > 4;
>> if (!alternative_has_cap_likely(ARM64_ALWAYS_BOOT))
>> return vabits_actual == VA_BITS;
>> return alternative_has_cap_unlikely(ARM64_HAS_VA52);
>> @@ -1059,6 +1065,8 @@ static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
>>
>> static inline p4d_t *pgd_to_folded_p4d(pgd_t *pgdp, unsigned long addr)
>> {
>> + if (IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE))
>> + return (p4d_t *)pgdp;
>> return (p4d_t *)PTR_ALIGN_DOWN(pgdp, PAGE_SIZE) + p4d_index(addr);
>> }
>>
>> diff --git a/arch/arm64/include/asm/sparsemem.h
>> b/arch/arm64/include/asm/sparsemem.h
>> index a05fdd54014f7..2daf1263ba638 100644
>> --- a/arch/arm64/include/asm/sparsemem.h
>> +++ b/arch/arm64/include/asm/sparsemem.h
>> @@ -17,6 +17,10 @@
>> * entries could not be created for vmemmap mappings.
>> * 16K follows 4K for simplicity.
>> */
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +#define SECTION_SIZE_BITS 29
>> +#else
>> #define SECTION_SIZE_BITS (PAGE_SIZE == SZ_64K ? 29 : 27)
>> +#endif
>>
>> #endif
>> diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
>> index a168f3337446f..9968320f83bc4 100644
>> --- a/arch/arm64/kernel/image-vars.h
>> +++ b/arch/arm64/kernel/image-vars.h
>> @@ -36,6 +36,17 @@ PROVIDE(__pi___memcpy =
>> __pi_memcpy);
>> PROVIDE(__pi___memmove = __pi_memmove);
>> PROVIDE(__pi___memset = __pi_memset);
>>
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +PROVIDE(__pi_ptg_page_shift = ptg_page_shift);
>> +PROVIDE(__pi_ptg_pmd_shift = ptg_pmd_shift);
>> +PROVIDE(__pi_ptg_pud_shift = ptg_pud_shift);
>> +PROVIDE(__pi_ptg_p4d_shift = ptg_p4d_shift);
>> +PROVIDE(__pi_ptg_pgdir_shift = ptg_pgdir_shift);
>> +PROVIDE(__pi_ptg_cont_pte_shift = ptg_cont_pte_shift);
>> +PROVIDE(__pi_ptg_cont_pmd_shift = ptg_cont_pmd_shift);
>> +PROVIDE(__pi_ptg_pgtable_levels = ptg_pgtable_levels);
>> +#endif /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> +
>> PROVIDE(__pi_id_aa64isar1_override = id_aa64isar1_override);
>> PROVIDE(__pi_id_aa64isar2_override = id_aa64isar2_override);
>> PROVIDE(__pi_id_aa64mmfr0_override = id_aa64mmfr0_override);
>> diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h
>> index 7bc3ba8979019..01502fc3b891b 100644
>> --- a/arch/arm64/kernel/image.h
>> +++ b/arch/arm64/kernel/image.h
>> @@ -47,7 +47,11 @@
>> #define __HEAD_FLAG_BE ARM64_IMAGE_FLAG_LE
>> #endif
>>
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +#define __HEAD_FLAG_PAGE_SIZE 0
>> +#else
>> #define __HEAD_FLAG_PAGE_SIZE ((PAGE_SHIFT - 10) / 2)
>> +#endif
>>
>> #define __HEAD_FLAG_PHYS_BASE 1
>>
>> diff --git a/arch/arm64/kernel/pi/map_kernel.c b/arch/arm64/kernel/pi/map_kernel.c
>> index deb8cd50b0b0c..22b3c70e04f9c 100644
>> --- a/arch/arm64/kernel/pi/map_kernel.c
>> +++ b/arch/arm64/kernel/pi/map_kernel.c
>> @@ -221,6 +221,49 @@ static void __init map_fdt(u64 fdt, int page_shift)
>> dsb(ishst);
>> }
>>
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> +static void __init ptg_init(int page_shift)
>> +{
>> + ptg_pgtable_levels =
>> + __ARM64_HW_PGTABLE_LEVELS(page_shift,
>> CONFIG_ARM64_VA_BITS);
>> +
>> + ptg_pgdir_shift = __ARM64_HW_PGTABLE_LEVEL_SHIFT(page_shift,
>> + 4 - ptg_pgtable_levels);
>> +
>> + ptg_p4d_shift = ptg_pgtable_levels >= 5 ?
>> + __ARM64_HW_PGTABLE_LEVEL_SHIFT(page_shift, 0) :
>> + ptg_pgdir_shift;
>> +
>> + ptg_pud_shift = ptg_pgtable_levels >= 4 ?
>> + __ARM64_HW_PGTABLE_LEVEL_SHIFT(page_shift, 1) :
>> + ptg_pgdir_shift;
>> +
>> + ptg_pmd_shift = ptg_pgtable_levels >= 3 ?
>> + __ARM64_HW_PGTABLE_LEVEL_SHIFT(page_shift, 2) :
>> + ptg_pgdir_shift;
>> +
>> + ptg_page_shift = page_shift;
>> +
>> + switch (page_shift) {
>> + case ARM64_PAGE_SHIFT_64K:
>> + ptg_cont_pte_shift = ptg_page_shift + 5;
>> + ptg_cont_pmd_shift = ptg_pmd_shift + 5;
>> + break;
>> + case ARM64_PAGE_SHIFT_16K:
>> + ptg_cont_pte_shift = ptg_page_shift + 7;
>> + ptg_cont_pmd_shift = ptg_pmd_shift + 5;
>> + break;
>> + default: /* ARM64_PAGE_SHIFT_4K */
>> + ptg_cont_pte_shift = ptg_page_shift + 4;
>> + ptg_cont_pmd_shift = ptg_pmd_shift + 4;
>> + }
>> +}
>> +#else /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> +static inline void ptg_init(int page_shift)
>> +{
>> +}
>> +#endif /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> +
>> asmlinkage void __init early_map_kernel(u64 boot_status, void *fdt)
>> {
>> static char const chosen_str[] __initconst = "/chosen";
>> @@ -247,6 +290,8 @@ asmlinkage void __init early_map_kernel(u64 boot_status, void
>> *fdt)
>> if (!page_shift)
>> page_shift = early_page_shift;
>>
>> + ptg_init(page_shift);
>> +
>> if (va_bits > 48) {
>> u64 page_size = early_page_size(page_shift);
>>
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 9bef7638342ef..c835a50b8b768 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -2424,6 +2424,16 @@ static void kvm_hyp_init_symbols(void)
>> kvm_nvhe_sym(id_aa64smfr0_el1_sys_val) =
>> read_sanitised_ftr_reg(SYS_ID_AA64SMFR0_EL1);
>> kvm_nvhe_sym(__icache_flags) = __icache_flags;
>> kvm_nvhe_sym(kvm_arm_vmid_bits) = kvm_arm_vmid_bits;
>> +#ifdef CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> + kvm_nvhe_sym(ptg_page_shift) = ptg_page_shift;
>> + kvm_nvhe_sym(ptg_pmd_shift) = ptg_pmd_shift;
>> + kvm_nvhe_sym(ptg_pud_shift) = ptg_pud_shift;
>> + kvm_nvhe_sym(ptg_p4d_shift) = ptg_p4d_shift;
>> + kvm_nvhe_sym(ptg_pgdir_shift) = ptg_pgdir_shift;
>> + kvm_nvhe_sym(ptg_cont_pte_shift) = ptg_cont_pte_shift;
>> + kvm_nvhe_sym(ptg_cont_pmd_shift) = ptg_cont_pmd_shift;
>> + kvm_nvhe_sym(ptg_pgtable_levels) = ptg_pgtable_levels;
>> +#endif /* CONFIG_ARM64_BOOT_TIME_PAGE_SIZE */
>> }
>>
>> static int __init kvm_hyp_init_protection(u32 hyp_va_bits)
>> diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile
>> b/arch/arm64/kvm/hyp/nvhe/Makefile
>> index b43426a493df5..a8fcbb84c7996 100644
>> --- a/arch/arm64/kvm/hyp/nvhe/Makefile
>> +++ b/arch/arm64/kvm/hyp/nvhe/Makefile
>> @@ -27,6 +27,7 @@ hyp-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-
>> init.o host.o
>> cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o ffa.o
>> hyp-obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
>> ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
>> +hyp-obj-$(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) += pgtable-geometry.o
>> hyp-obj-$(CONFIG_LIST_HARDENED) += list_debug.o
>> hyp-obj-y += $(lib-objs)
>>
>> diff --git a/arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c
>> b/arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c
>> new file mode 100644
>> index 0000000000000..17f807450a31a
>> --- /dev/null
>> +++ b/arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c
>> @@ -0,0 +1,16 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2024 ARM Ltd.
>> + */
>> +
>> +#include <linux/cache.h>
>> +#include <asm/pgtable-geometry.h>
>> +
>> +int ptg_page_shift __ro_after_init;
>> +int ptg_pmd_shift __ro_after_init;
>> +int ptg_pud_shift __ro_after_init;
>> +int ptg_p4d_shift __ro_after_init;
>> +int ptg_pgdir_shift __ro_after_init;
>> +int ptg_cont_pte_shift __ro_after_init;
>> +int ptg_cont_pmd_shift __ro_after_init;
>> +int ptg_pgtable_levels __ro_after_init;
>> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
>> index 60454256945b8..2ba30d06b35fe 100644
>> --- a/arch/arm64/mm/Makefile
>> +++ b/arch/arm64/mm/Makefile
>> @@ -3,6 +3,7 @@ obj-y := dma-mapping.o extable.o
>> fault.o init.o \
>> cache.o copypage.o flush.o \
>> ioremap.o mmap.o pgd.o mmu.o \
>> context.o proc.o pageattr.o fixmap.o
>> +obj-$(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) += pgtable-geometry.o
>> obj-$(CONFIG_ARM64_CONTPTE) += contpte.o
>> obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
>> obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
>> diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c
>> index 4b106510358b1..c052d0dcb0c69 100644
>> --- a/arch/arm64/mm/pgd.c
>> +++ b/arch/arm64/mm/pgd.c
>> @@ -21,10 +21,12 @@ static bool pgdir_is_page_size(void)
>> {
>> if (PGD_SIZE == PAGE_SIZE)
>> return true;
>> - if (CONFIG_PGTABLE_LEVELS == 4)
>> - return !pgtable_l4_enabled();
>> - if (CONFIG_PGTABLE_LEVELS == 5)
>> - return !pgtable_l5_enabled();
>> + if (!IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE)) {
>> + if (CONFIG_PGTABLE_LEVELS == 4)
>> + return !pgtable_l4_enabled();
>> + if (CONFIG_PGTABLE_LEVELS == 5)
>> + return !pgtable_l5_enabled();
>> + }
>> return false;
>> }
>>
>> diff --git a/arch/arm64/mm/pgtable-geometry.c b/arch/arm64/mm/pgtable-
>> geometry.c
>> new file mode 100644
>> index 0000000000000..ba50637f1e9d0
>> --- /dev/null
>> +++ b/arch/arm64/mm/pgtable-geometry.c
>> @@ -0,0 +1,24 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2024 ARM Ltd.
>> + */
>> +
>> +#include <linux/cache.h>
>> +#include <asm/pgtable-geometry.h>
>> +
>> +/*
>> + * TODO: These should be __ro_after_init, but we need to write to them from the
>> + * pi code where they are mapped in the early page table as read-only.
>> + * __ro_after_init doesn't become writable until later when the swapper pgtable
>> + * is fully set up. We should update the early page table to map __ro_after_init
>> + * as read-write.
>> + */
>> +
>> +int ptg_page_shift __read_mostly;
>> +int ptg_pmd_shift __read_mostly;
>
> I found that ptg_page_shift and ptg_pmd_shift need
> EXPORT_SYMBOL_GPL for cases where code compiled
> as a module is using PAGE_SIZE/PAGE_SHIFT or
> PMD_SIZE/PMD_SHIFT. Some of the others below
> might also need EXPORT_SYMBOL_GPL.

Ahh good spot - thanks! I'll fix this in the next version.

I wonder if these should really be EXPORT_SYMBOL() and not limited to GPL? I
guess having access to PAGE_SIZE is a pretty fundamental thing? Anybody know the
policy here?

Thanks,
Ryan

>
> Michael
>
>> +int ptg_pud_shift __read_mostly;
>> +int ptg_p4d_shift __read_mostly;
>> +int ptg_pgdir_shift __read_mostly;
>> +int ptg_cont_pte_shift __read_mostly;
>> +int ptg_cont_pmd_shift __read_mostly;
>> +int ptg_pgtable_levels __read_mostly;
>> diff --git a/drivers/firmware/efi/libstub/arm64.c
>> b/drivers/firmware/efi/libstub/arm64.c
>> index e57cd3de0a00f..8db9dba7d5423 100644
>> --- a/drivers/firmware/efi/libstub/arm64.c
>> +++ b/drivers/firmware/efi/libstub/arm64.c
>> @@ -68,7 +68,8 @@ efi_status_t check_platform_features(void)
>> efi_novamap = true;
>>
>> /* UEFI mandates support for 4 KB granularity, no need to check */
>> - if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
>> + if (IS_ENABLED(CONFIG_ARM64_4K_PAGES) ||
>> + IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE))
>> return EFI_SUCCESS;
>>
>> tg = (read_cpuid(ID_AA64MMFR0_EL1) >>
>> ID_AA64MMFR0_EL1_TGRAN_SHIFT) & 0xf;
>> --
>> 2.43.0
>>
>