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Date:   Sat, 23 Mar 2019 17:40:12 +0200
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Anup Patel <Anup.Patel@wdc.com>
Cc:     Palmer Dabbelt <palmer@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Atish Patra <Atish.Patra@wdc.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Christoph Hellwig <hch@infradead.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 3/5] RISC-V: Allow booting kernel from any 4KB aligned
 address
References: <20190321094710.16552-1-anup.patel@wdc.com>
 <20190321094710.16552-4-anup.patel@wdc.com>
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On Thu, Mar 21, 2019 at 09:47:51AM +0000, Anup Patel wrote:
> Currently, we have to boot RISCV64 kernel from a 2MB aligned physical
> address and RISCV32 kernel from a 4MB aligned physical address. This
> constraint is because initial pagetable setup (i.e. setup_vm()) maps
> entire RAM using hugepages (i.e. 2MB for 3-level pagetable and 4MB for
> 2-level pagetable).
> 
> Further, the above booting contraint also results in memory wastage
> because if we boot kernel from some <xyz> address (which is not same as
> RAM start address) then RISCV kernel will map PAGE_OFFSET virtual address
> lineraly to <xyz> physical address and memory between RAM start and <xyz>
> will be reserved/unusable.
> 
> For example, RISCV64 kernel booted from 0x80200000 will waste 2MB of RAM
> and RISCV32 kernel booted from 0x80400000 will waste 4MB of RAM.
> 
> This patch re-writes the initial pagetable setup code to allow booting
> RISV32 and RISCV64 kernel from any 4KB (i.e. PAGE_SIZE) aligned address.
> 
> To achieve this:
> 1. We add kconfig option BOOT_PAGE_ALIGNED. When it is enabled we use
>    4KB mappings in initial page table setup otherwise we use 2MB/4MB
>    mappings.
> 2. We map kernel and dtb (few MBs) in setup_vm() (called from head.S)
> 3. Once we reach paging_init() (called from setup_arch()) after
>    memblock setup, we map all available memory banks.
> 
> With this patch in-place, the booting constraint for RISCV32 and RISCV64
> kernel is much more relaxed when CONFIG_BOOT_PAGE_ALIGNED=y and we can
> now boot kernel very close to RAM start thereby minimizng memory wastage.

I have no general objection, but I presume the patch will be significantly
simplified if the addition of 4K pages support will follow the removal of
the trampoline_pd_dir. 

That said, I didn't look into the details, since they will change
substantially, only some comments on the Kconfig part.

On the high level, have you considered using large pages in setup_vm() and
the remapping everything with 4K pages in setup_vm_final()?  This might
save you the whole ops-> churn.
 
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> ---
>  arch/riscv/Kconfig                  |  11 +
>  arch/riscv/include/asm/fixmap.h     |   5 +
>  arch/riscv/include/asm/pgtable-64.h |   5 +
>  arch/riscv/include/asm/pgtable.h    |   6 +-
>  arch/riscv/kernel/head.S            |   1 +
>  arch/riscv/kernel/setup.c           |   4 +-
>  arch/riscv/mm/init.c                | 402 ++++++++++++++++++++++++----
>  7 files changed, 378 insertions(+), 56 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index eb56c82d8aa1..1b0c66f7aba3 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -172,6 +172,17 @@ config SMP
>  
>  	  If you don't know what to do here, say N.
>  
> +config BOOT_PAGE_ALIGNED
> +	bool "Allow booting from page aligned address"

default no, please

> +	help
> +	  This enables support for booting kernel from any page aligned
> +	  address (i.e. 4KB aligned). This option is particularly useful
> +	  on systems with very less RAM (few MBs) because using it we

                              ^ small

> +	  can boot kernel closer RAM start thereby reducing unusable RAM
> +	  below kernel.
> +
> +	  If you don't know what to do here, say N.
> +
>  config NR_CPUS
>  	int "Maximum number of CPUs (2-32)"
>  	range 2 32
> diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
> index 57afe604b495..5cf53dd882e5 100644
> --- a/arch/riscv/include/asm/fixmap.h
> +++ b/arch/riscv/include/asm/fixmap.h
> @@ -21,6 +21,11 @@
>   */
>  enum fixed_addresses {
>  	FIX_HOLE,
> +#define FIX_FDT_SIZE	SZ_1M
> +	FIX_FDT_END,
> +	FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1,
> +	FIX_PTE,
> +	FIX_PMD,
>  	FIX_EARLYCON_MEM_BASE,
>  	__end_of_fixed_addresses
>  };
> diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
> index 7aa0ea9bd8bb..56ecc3dc939d 100644
> --- a/arch/riscv/include/asm/pgtable-64.h
> +++ b/arch/riscv/include/asm/pgtable-64.h
> @@ -78,6 +78,11 @@ static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
>  	return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
>  }
>  
> +static inline unsigned long _pmd_pfn(pmd_t pmd)
> +{
> +	return pmd_val(pmd) >> _PAGE_PFN_SHIFT;
> +}
> +
>  #define pmd_ERROR(e) \
>  	pr_err("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e))
>  
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 1141364d990e..05fa2115e736 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -121,12 +121,16 @@ static inline void pmd_clear(pmd_t *pmdp)
>  	set_pmd(pmdp, __pmd(0));
>  }
>  
> -
>  static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot)
>  {
>  	return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
>  }
>  
> +static inline unsigned long _pgd_pfn(pgd_t pgd)
> +{
> +	return pgd_val(pgd) >> _PAGE_PFN_SHIFT;
> +}
> +
>  #define pgd_index(addr) (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
>  
>  /* Locate an entry in the page global directory */
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 7966262b4f9d..12a3ec5eb8ab 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -63,6 +63,7 @@ clear_bss_done:
>  	/* Initialize page tables and relocate to virtual addresses */
>  	la sp, init_thread_union + THREAD_SIZE
>  	la a0, _start
> +	mv a1, s1
>  	call setup_vm
>  	call relocate
>  
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index ecb654f6a79e..acdd0f74982b 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -30,6 +30,7 @@
>  #include <linux/sched/task.h>
>  #include <linux/swiotlb.h>
>  
> +#include <asm/fixmap.h>
>  #include <asm/setup.h>
>  #include <asm/sections.h>
>  #include <asm/pgtable.h>
> @@ -62,7 +63,8 @@ unsigned long boot_cpu_hartid;
>  
>  void __init parse_dtb(unsigned int hartid, void *dtb)
>  {
> -	if (early_init_dt_scan(__va(dtb)))
> +	dtb = (void *)fix_to_virt(FIX_FDT) + ((uintptr_t)dtb & ~PAGE_MASK);
> +	if (early_init_dt_scan(dtb))
>  		return;
>  
>  	pr_err("No DTB passed to the kernel\n");
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index e38f8195e45b..c389fbfeccd8 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1,14 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
>  /*
> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
>   * Copyright (C) 2012 Regents of the University of California
> - *
> - *   This program is free software; you can redistribute it and/or
> - *   modify it under the terms of the GNU General Public License
> - *   as published by the Free Software Foundation, version 2.
> - *
> - *   This program is distributed in the hope that it will be useful,
> - *   but WITHOUT ANY WARRANTY; without even the implied warranty of
> - *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> - *   GNU General Public License for more details.
>   */
>  
>  #include <linux/init.h>
> @@ -43,13 +36,6 @@ void setup_zero_page(void)
>  	memset((void *)empty_zero_page, 0, PAGE_SIZE);
>  }
>  
> -void __init paging_init(void)
> -{
> -	setup_zero_page();
> -	local_flush_tlb_all();
> -	zone_sizes_init();
> -}
> -
>  void __init mem_init(void)
>  {
>  #ifdef CONFIG_FLATMEM
> @@ -143,18 +129,36 @@ void __init setup_bootmem(void)
>  	}
>  }
>  
> +#define MAX_EARLY_MAPPING_SIZE	SZ_128M
> +
>  pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>  pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>  
>  #ifndef __PAGETABLE_PMD_FOLDED
> -#define NUM_SWAPPER_PMDS ((uintptr_t)-PAGE_OFFSET >> PGDIR_SHIFT)
> -pmd_t swapper_pmd[PTRS_PER_PMD*((-PAGE_OFFSET)/PGDIR_SIZE)] __page_aligned_bss;
> -pmd_t trampoline_pmd[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
> +#if MAX_EARLY_MAPPING_SIZE < PGDIR_SIZE
> +#define NUM_SWAPPER_PMDS	1UL
> +#else
> +#define NUM_SWAPPER_PMDS	(MAX_EARLY_MAPPING_SIZE/PGDIR_SIZE)
> +#endif
> +#define NUM_TRAMPOLINE_PMDS	1UL
> +pmd_t swapper_pmd[PTRS_PER_PMD*NUM_SWAPPER_PMDS] __page_aligned_bss;
> +pmd_t trampoline_pmd[PTRS_PER_PMD*NUM_TRAMPOLINE_PMDS]
> +	__initdata __aligned(PAGE_SIZE);
>  pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
> +#define NUM_SWAPPER_PTES	(MAX_EARLY_MAPPING_SIZE/PMD_SIZE)
> +#else
> +#define NUM_SWAPPER_PTES	(MAX_EARLY_MAPPING_SIZE/PGDIR_SIZE)
>  #endif
>  
> +#define NUM_TRAMPOLINE_PTES	1UL
> +
> +pte_t swapper_pte[PTRS_PER_PTE*NUM_SWAPPER_PTES] __page_aligned_bss;
> +pte_t trampoline_pte[PTRS_PER_PTE*NUM_TRAMPOLINE_PTES]
> +	__initdata __aligned(PAGE_SIZE);
>  pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>  
> +uintptr_t map_size;
> +
>  void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>  {
>  	unsigned long addr = __fix_to_virt(idx);
> @@ -172,6 +176,13 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>  	}
>  }
>  
> +struct mapping_ops {
> +	pte_t *(*get_pte_virt)(phys_addr_t pa);
> +	phys_addr_t (*alloc_pte)(uintptr_t va, uintptr_t load_pa);
> +	pmd_t *(*get_pmd_virt)(phys_addr_t pa);
> +	phys_addr_t (*alloc_pmd)(uintptr_t va, uintptr_t load_pa);
> +};
> +
>  static inline void *__load_addr(void *ptr, uintptr_t load_pa)
>  {
>  	extern char _start;
> @@ -186,64 +197,347 @@ static inline void *__load_addr(void *ptr, uintptr_t load_pa)
>  #define __load_va(ptr, load_pa)	__load_addr(ptr, load_pa)
>  #define __load_pa(ptr, load_pa)	((uintptr_t)__load_addr(ptr, load_pa))
>  
> -asmlinkage void __init setup_vm(uintptr_t load_pa)
> +static phys_addr_t __init final_alloc_pgtable(void)
> +{
> +	return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
> +}
> +
> +static pte_t *__init early_get_pte_virt(phys_addr_t pa)
> +{
> +	return (pte_t *)((uintptr_t)pa);
> +}
> +
> +static pte_t *__init final_get_pte_virt(phys_addr_t pa)
> +{
> +	clear_fixmap(FIX_PTE);
> +
> +	return (pte_t *)set_fixmap_offset(FIX_PTE, pa);
> +}
> +
> +static phys_addr_t __init early_alloc_trampoline_pte(uintptr_t va,
> +						     uintptr_t load_pa)
> +{
> +	pte_t *base = __load_va(trampoline_pte, load_pa);
> +	uintptr_t pte_num = ((va - PAGE_OFFSET) >> PMD_SHIFT);
> +
> +	BUG_ON(pte_num >= NUM_TRAMPOLINE_PTES);
> +
> +	return (uintptr_t)&base[pte_num * PTRS_PER_PTE];
> +}
> +
> +static phys_addr_t __init early_alloc_swapper_pte(uintptr_t va,
> +						  uintptr_t load_pa)
> +{
> +	pte_t *base = __load_va(swapper_pte, load_pa);
> +	uintptr_t pte_num = ((va - PAGE_OFFSET) >> PMD_SHIFT);
> +
> +	BUG_ON(pte_num >= NUM_SWAPPER_PTES);
> +
> +	return (uintptr_t)&base[pte_num * PTRS_PER_PTE];
> +}
> +
> +static phys_addr_t __init final_alloc_pte(uintptr_t va, uintptr_t load_pa)
> +{
> +	return final_alloc_pgtable();
> +}
> +
> +static void __init create_pte_mapping(pte_t *ptep,
> +				      uintptr_t va, phys_addr_t pa,
> +				      phys_addr_t sz, pgprot_t prot)
>  {
> -	uintptr_t i;
> +	uintptr_t pte_index = pte_index(va);
> +
> +	BUG_ON(sz != PAGE_SIZE);
> +
> +	if (pte_none(ptep[pte_index]))
> +		ptep[pte_index] = pfn_pte(PFN_DOWN(pa), prot);
> +}
> +
>  #ifndef __PAGETABLE_PMD_FOLDED
> +static pmd_t *__init early_get_pmd_virt(phys_addr_t pa)
> +{
> +	return (pmd_t *)((uintptr_t)pa);
> +}
> +
> +static pmd_t *__init final_get_pmd_virt(phys_addr_t pa)
> +{
> +	clear_fixmap(FIX_PMD);
> +
> +	return (pmd_t *)set_fixmap_offset(FIX_PMD, pa);
> +}
> +
> +static phys_addr_t __init early_alloc_trampoline_pmd(uintptr_t va,
> +						     uintptr_t load_pa)
> +{
> +	pmd_t *base = __load_va(trampoline_pmd, load_pa);
> +	uintptr_t pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
> +
> +	BUG_ON(pmd_num >= NUM_TRAMPOLINE_PMDS);
> +
> +	return (uintptr_t)&base[pmd_num * PTRS_PER_PMD];
> +}
> +
> +static phys_addr_t __init early_alloc_swapper_pmd(uintptr_t va,
> +						  uintptr_t load_pa)
> +{
> +	pmd_t *base = __load_va(swapper_pmd, load_pa);
> +	uintptr_t pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
> +
> +	BUG_ON(pmd_num >= NUM_SWAPPER_PMDS);
> +
> +	return (uintptr_t)&base[pmd_num * PTRS_PER_PMD];
> +}
> +
> +static phys_addr_t __init final_alloc_pmd(uintptr_t va, uintptr_t load_pa)
> +{
> +	return final_alloc_pgtable();
> +}
> +
> +static void __init create_pmd_mapping(pmd_t *pmdp,
> +				      uintptr_t va, phys_addr_t pa,
> +				      phys_addr_t sz, pgprot_t prot,
> +				      uintptr_t ops_load_pa,
> +				      struct mapping_ops *ops)
> +{
> +	pte_t *ptep;
> +	phys_addr_t pte_phys;
> +	uintptr_t pmd_index = pmd_index(va);
> +
> +	if (sz == PMD_SIZE) {
> +		if (pmd_none(pmdp[pmd_index]))
> +			pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pa), prot);
> +		return;
> +	}
> +
> +	if (pmd_none(pmdp[pmd_index])) {
> +		pte_phys = ops->alloc_pte(va, ops_load_pa);
> +		pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pte_phys),
> +					  __pgprot(_PAGE_TABLE));
> +		ptep = ops->get_pte_virt(pte_phys);
> +		memset(ptep, 0, PAGE_SIZE);
> +	} else {
> +		pte_phys = PFN_PHYS(_pmd_pfn(pmdp[pmd_index]));
> +		ptep = ops->get_pte_virt(pte_phys);
> +	}
> +
> +	create_pte_mapping(ptep, va, pa, sz, prot);
> +}
> +
> +static void __init create_pgd_mapping(pgd_t *pgdp,
> +				      uintptr_t va, phys_addr_t pa,
> +				      phys_addr_t sz, pgprot_t prot,
> +				      uintptr_t ops_load_pa,
> +				      struct mapping_ops *ops)
> +{
>  	pmd_t *pmdp;
> +	phys_addr_t pmd_phys;
> +	uintptr_t pgd_index = pgd_index(va);
> +
> +	if (sz == PGDIR_SIZE) {
> +		if (pgd_val(pgdp[pgd_index]) == 0)
> +			pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pa), prot);
> +		return;
> +	}
> +
> +	if (pgd_val(pgdp[pgd_index]) == 0) {
> +		pmd_phys = ops->alloc_pmd(va, ops_load_pa);
> +		pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pmd_phys),
> +					  __pgprot(_PAGE_TABLE));
> +		pmdp = ops->get_pmd_virt(pmd_phys);
> +		memset(pmdp, 0, PAGE_SIZE);
> +	} else {
> +		pmd_phys = PFN_PHYS(_pgd_pfn(pgdp[pgd_index]));
> +		pmdp = ops->get_pmd_virt(pmd_phys);
> +	}
> +
> +	create_pmd_mapping(pmdp, va, pa, sz, prot, ops_load_pa, ops);
> +}
> +#else
> +static void __init create_pgd_mapping(pgd_t *pgdp,
> +				      uintptr_t va, phys_addr_t pa,
> +				      phys_addr_t sz, pgprot_t prot,
> +				      uintptr_t ops_load_pa,
> +				      struct mapping_ops *ops)
> +{
> +	pte_t *ptep;
> +	phys_addr_t pte_phys;
> +	uintptr_t pgd_index = pgd_index(va);
> +
> +	if (sz == PGDIR_SIZE) {
> +		if (pgd_val(pgdp[pgd_index]) == 0)
> +			pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pa), prot);
> +		return;
> +	}
> +
> +	if (pgd_val(pgdp[pgd_index]) == 0) {
> +		pte_phys = ops->alloc_pte(va, ops_load_pa);
> +		pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pte_phys),
> +					  __pgprot(_PAGE_TABLE));
> +		ptep = ops->get_pte_virt(pte_phys);
> +		memset(ptep, 0, PAGE_SIZE);
> +	} else {
> +		pte_phys = PFN_PHYS(_pgd_pfn(pgdp[pgd_index]));
> +		ptep = ops->get_pte_virt(pte_phys);
> +	}
> +
> +	create_pte_mapping(ptep, va, pa, sz, prot);
> +}
> +#endif
> +
> +static uintptr_t __init best_map_size(uintptr_t load_pa, phys_addr_t size)
> +{
> +#ifdef CONFIG_BOOT_PAGE_ALIGNED
> +	uintptr_t map_sz = PAGE_SIZE;
> +#else
> +#ifndef __PAGETABLE_PMD_FOLDED
> +	uintptr_t map_sz = PMD_SIZE;
> +#else
> +	uintptr_t map_sz = PGDIR_SIZE;
> +#endif
>  #endif
> -	pgd_t *pgdp;
> +
> +#ifndef __PAGETABLE_PMD_FOLDED
> +	if (!(load_pa & (PMD_SIZE - 1)) &&
> +	    (size >= PMD_SIZE) &&
> +	    (map_sz < PMD_SIZE))
> +		map_sz = PMD_SIZE;
> +#endif
> +
> +	if (!(load_pa & (PGDIR_SIZE - 1)) &&
> +	    (size >= PGDIR_SIZE) &&
> +	    (map_sz < PGDIR_SIZE))
> +		map_sz = PGDIR_SIZE;
> +
> +	return map_sz;
> +}
> +
> +asmlinkage void __init setup_vm(uintptr_t load_pa, uintptr_t dtb_pa)
> +{
>  	phys_addr_t map_pa;
> +	uintptr_t va, end_va;
> +	uintptr_t load_sz = __load_pa(&_end, load_pa) - load_pa;
>  	pgprot_t tableprot = __pgprot(_PAGE_TABLE);
>  	pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
> +	struct mapping_ops tramp_ops, swap_ops;
>  
>  	va_pa_offset = PAGE_OFFSET - load_pa;
>  	pfn_base = PFN_DOWN(load_pa);
> +	map_size = best_map_size(load_pa, PGDIR_SIZE);
>  
>  	/* Sanity check alignment and size */
>  	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
> -	BUG_ON((load_pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0);
> +	BUG_ON((load_pa % map_size) != 0);
> +	BUG_ON(load_sz > MAX_EARLY_MAPPING_SIZE);
>  
> -#ifndef __PAGETABLE_PMD_FOLDED
> -	pgdp = __load_va(trampoline_pg_dir, load_pa);
> -	map_pa = __load_pa(trampoline_pmd, load_pa);
> -	pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
> -		pfn_pgd(PFN_DOWN(map_pa), tableprot);
> -	trampoline_pmd[0] = pfn_pmd(PFN_DOWN(load_pa), prot);
> +	/* Setup trampoline mapping ops */
> +	tramp_ops.get_pte_virt = __load_va(early_get_pte_virt, load_pa);
> +	tramp_ops.alloc_pte = __load_va(early_alloc_trampoline_pte, load_pa);
> +	tramp_ops.get_pmd_virt = NULL;
> +	tramp_ops.alloc_pmd = NULL;
>  
> -	pgdp = __load_va(swapper_pg_dir, load_pa);
> +	/* Setup swapper mapping ops */
> +	swap_ops.get_pte_virt = __load_va(early_get_pte_virt, load_pa);
> +	swap_ops.alloc_pte = __load_va(early_alloc_swapper_pte, load_pa);
> +	swap_ops.get_pmd_virt = NULL;
> +	swap_ops.alloc_pmd = NULL;
>  
> -	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
> -		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
> +#ifndef __PAGETABLE_PMD_FOLDED
> +	/* Update trampoline mapping ops for PMD */
> +	tramp_ops.get_pmd_virt = __load_va(early_get_pmd_virt, load_pa);
> +	tramp_ops.alloc_pmd = __load_va(early_alloc_trampoline_pmd, load_pa);
>  
> -		map_pa = __load_pa(swapper_pmd, load_pa);
> -		pgdp[o] = pfn_pgd(PFN_DOWN(map_pa) + i, tableprot);
> -	}
> -	pmdp = __load_va(swapper_pmd, load_pa);
> -	for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++)
> -		pmdp[i] = pfn_pmd(PFN_DOWN(load_pa + i * PMD_SIZE), prot);
> +	/* Update swapper mapping ops for PMD */
> +	swap_ops.get_pmd_virt = __load_va(early_get_pmd_virt, load_pa);
> +	swap_ops.alloc_pmd = __load_va(early_alloc_swapper_pmd, load_pa);
>  
> +	/* Setup swapper PGD and PMD for fixmap */
>  	map_pa = __load_pa(fixmap_pmd, load_pa);
> -	pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
> -		pfn_pgd(PFN_DOWN(map_pa), tableprot);
> -	pmdp = __load_va(fixmap_pmd, load_pa);
> +	create_pgd_mapping(__load_va(swapper_pg_dir, load_pa),
> +			   FIXADDR_START, map_pa, PGDIR_SIZE, tableprot,
> +			   load_pa, &swap_ops);
>  	map_pa = __load_pa(fixmap_pte, load_pa);
> -	fixmap_pmd[(FIXADDR_START >> PMD_SHIFT) % PTRS_PER_PMD] =
> -		pfn_pmd(PFN_DOWN(map_pa), tableprot);
> +	create_pmd_mapping(__load_va(fixmap_pmd, load_pa),
> +			   FIXADDR_START, map_pa, PMD_SIZE, tableprot,
> +			   load_pa, &swap_ops);
>  #else
> -	pgdp = __load_va(trampoline_pg_dir, load_pa);
> -	pgdp[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
> -		pfn_pgd(PFN_DOWN(load_pa), prot);
> +	/* Setup swapper PGD for fixmap */
> +	map_pa = __load_pa(fixmap_pte, load_pa);
> +	create_pgd_mapping(__load_va(swapper_pg_dir, load_pa),
> +			   FIXADDR_START, map_pa, PGDIR_SIZE, tableprot,
> +			   load_pa, &swap_ops);
> +#endif
>  
> -	pgdp = __load_va(swapper_pg_dir, load_pa);
> -	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
> -		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
> +	/* Setup trampoling PGD covering first few MBs of kernel */
> +	end_va = PAGE_OFFSET + PAGE_SIZE*PTRS_PER_PTE;
> +	for (va = PAGE_OFFSET; va < end_va; va += map_size)
> +		create_pgd_mapping(__load_va(trampoline_pg_dir, load_pa),
> +				   va, load_pa + (va - PAGE_OFFSET),
> +				   map_size, prot, load_pa, &tramp_ops);
> +
> +	/*
> +	 * Setup swapper PGD covering entire kernel which will allows
> +	 * us to reach paging_init(). We map all memory banks later in
> +	 * setup_vm_final() below.
> +	 */
> +	end_va = PAGE_OFFSET + load_sz;
> +	for (va = PAGE_OFFSET; va < end_va; va += map_size)
> +		create_pgd_mapping(__load_va(swapper_pg_dir, load_pa),
> +				   va, load_pa + (va - PAGE_OFFSET),
> +				   map_size, prot, load_pa, &swap_ops);
> +
> +	/* Create fixed mapping for early parsing of FDT */
> +	end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
> +	for (va = __fix_to_virt(FIX_FDT); va < end_va; va += PAGE_SIZE)
> +		create_pte_mapping(__load_va(fixmap_pte, load_pa),
> +				   va, dtb_pa + (va - __fix_to_virt(FIX_FDT)),
> +				   PAGE_SIZE, prot);
> +}
>  
> -		pgdp[o] = pfn_pgd(PFN_DOWN(load_pa + i * PGDIR_SIZE), prot);
> -	}
> +static void __init setup_vm_final(void)
> +{
> +	phys_addr_t pa, start, end;
> +	struct memblock_region *reg;
> +	struct mapping_ops ops;
> +	pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
>  
> -	map_pa = __load_pa(fixmap_pte, load_pa);
> -	pgdp[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
> -		pfn_pgd(PFN_DOWN(map_pa), tableprot);
> +	/* Setup mapping ops */
> +	ops.get_pte_virt = final_get_pte_virt;
> +	ops.alloc_pte = final_alloc_pte;
> +#ifndef __PAGETABLE_PMD_FOLDED
> +	ops.get_pmd_virt = final_get_pmd_virt;
> +	ops.alloc_pmd = final_alloc_pmd;
> +#else
> +	ops.get_pmd_virt = NULL;
> +	ops.alloc_pmd = NULL;
>  #endif
> +
> +	/* Map all memory banks */
> +	for_each_memblock(memory, reg) {
> +		start = reg->base;
> +		end = start + reg->size;
> +
> +		if (start >= end)
> +			break;
> +		if (memblock_is_nomap(reg))
> +			continue;
> +		if (start <= __pa(PAGE_OFFSET) &&
> +		    __pa(PAGE_OFFSET) < end)
> +			start = __pa(PAGE_OFFSET);
> +
> +		for (pa = start; pa < end; pa += map_size)
> +			create_pgd_mapping(swapper_pg_dir,
> +					   (uintptr_t)__va(pa), pa,
> +					   map_size, prot, 0, &ops);
> +	}
> +
> +	clear_fixmap(FIX_PTE);
> +	clear_fixmap(FIX_PMD);
> +}
> +
> +void __init paging_init(void)
> +{
> +	setup_vm_final();
> +	setup_zero_page();
> +	local_flush_tlb_all();
> +	zone_sizes_init();
>  }
> -- 
> 2.17.1
> 

-- 
Sincerely yours,
Mike.