[PATCH v3 5/6] ARM: mm: Recreate kernel mappings in early_paging_init()

[Nicolas Pitre]

On Thu, 3 Oct 2013, Santosh Shilimkar wrote:

> This patch adds a step in the init sequence, in order to recreate
> the kernel code/data page table mappings prior to full paging
> initialization.  This is necessary on LPAE systems that run out of
> a physical address space outside the 4G limit.  On these systems,
> this implementation provides a machine descriptor hook that allows
> the PHYS_OFFSET to be overridden in a machine specific fashion.
> 
> Cc: Nicolas Pitre <nico at linaro.org>
> Cc: Russell King <linux at arm.linux.org.uk>
> 
> Signed-off-by: R Sricharan <r.sricharan at ti.com>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>

Acked-by: Nicolas Pitre <nico at linaro.org>

> ---
>  arch/arm/include/asm/mach/arch.h |    1 +
>  arch/arm/kernel/setup.c          |    3 ++
>  arch/arm/mm/mmu.c                |   82 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 86 insertions(+)
> 
> diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
> index 402a2bc..17a3fa2 100644
> --- a/arch/arm/include/asm/mach/arch.h
> +++ b/arch/arm/include/asm/mach/arch.h
> @@ -49,6 +49,7 @@ struct machine_desc {
>  	bool			(*smp_init)(void);
>  	void			(*fixup)(struct tag *, char **,
>  					 struct meminfo *);
> +	void			(*init_meminfo)(void);
>  	void			(*reserve)(void);/* reserve mem blocks	*/
>  	void			(*map_io)(void);/* IO mapping function	*/
>  	void			(*init_early)(void);
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 0e1e2b3..b9a6dac 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -73,6 +73,7 @@ __setup("fpe=", fpe_setup);
>  #endif
>  
>  extern void paging_init(const struct machine_desc *desc);
> +extern void early_paging_init(const struct machine_desc *, struct proc_info_list *);
>  extern void sanity_check_meminfo(void);
>  extern enum reboot_mode reboot_mode;
>  extern void setup_dma_zone(const struct machine_desc *desc);
> @@ -878,6 +879,8 @@ void __init setup_arch(char **cmdline_p)
>  	parse_early_param();
>  
>  	sort(&meminfo.bank, meminfo.nr_banks, sizeof(meminfo.bank[0]), meminfo_cmp, NULL);
> +
> +	early_paging_init(mdesc, lookup_processor_type(read_cpuid_id()));
>  	sanity_check_meminfo();
>  	arm_memblock_init(&meminfo, mdesc);
>  
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index b1d17ee..47c7497 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -28,6 +28,7 @@
>  #include <asm/highmem.h>
>  #include <asm/system_info.h>
>  #include <asm/traps.h>
> +#include <asm/procinfo.h>
>  
>  #include <asm/mach/arch.h>
>  #include <asm/mach/map.h>
> @@ -1315,6 +1316,87 @@ static void __init map_lowmem(void)
>  	}
>  }
>  
> +#ifdef CONFIG_ARM_LPAE
> +extern void fixup_pv_table(const void *, unsigned long);
> +extern const void *__pv_table_begin, *__pv_table_end;
> +
> +/*
> + * early_paging_init() recreates boot time page table setup, allowing machines
> + * to switch over to a high (>4G) address space on LPAE systems
> + */
> +void __init early_paging_init(const struct machine_desc *mdesc,
> +			      struct proc_info_list *procinfo)
> +{
> +	pmdval_t pmdprot = procinfo->__cpu_mm_mmu_flags;
> +	unsigned long map_start, map_end;
> +	pgd_t *pgd0, *pgdk;
> +	pud_t *pud0, *pudk;
> +	pmd_t *pmd0, *pmdk;
> +	phys_addr_t phys;
> +	int i;
> +
> +	/* remap kernel code and data */
> +	map_start = init_mm.start_code;
> +	map_end   = init_mm.brk;
> +
> +	/* get a handle on things... */
> +	pgd0 = pgd_offset_k(0);
> +	pud0 = pud_offset(pgd0, 0);
> +	pmd0 = pmd_offset(pud0, 0);
> +
> +	pgdk = pgd_offset_k(map_start);
> +	pudk = pud_offset(pgdk, map_start);
> +	pmdk = pmd_offset(pudk, map_start);
> +
> +	phys = PHYS_OFFSET;
> +
> +	if (mdesc->init_meminfo) {
> +		mdesc->init_meminfo();
> +		/* Run the patch stub to update the constants */
> +		fixup_pv_table(&__pv_table_begin,
> +			(&__pv_table_end - &__pv_table_begin) << 2);
> +
> +		/*
> +		 * Cache cleaning operations for self-modifying code
> +		 * We should clean the entries by MVA but running a
> +		 * for loop over every pv_table entry pointer would
> +		 * just complicate the code.
> +		 */
> +		flush_cache_louis();
> +		dsb();
> +		isb();
> +	}
> +
> +	/* remap level 1 table */
> +	for (i = 0; i < PTRS_PER_PGD; i++) {
> +		*pud0++ = __pud(__pa(pmd0) | PMD_TYPE_TABLE | L_PGD_SWAPPER);
> +		pmd0 += PTRS_PER_PMD;
> +	}
> +
> +	/* remap pmds for kernel mapping */
> +	phys = __pa(map_start) & PMD_MASK;
> +	do {
> +		*pmdk++ = __pmd(phys | pmdprot);
> +		phys += PMD_SIZE;
> +	} while (phys < map_end);
> +
> +	flush_cache_all();
> +	cpu_set_ttbr(0, __pa(pgd0));
> +	cpu_set_ttbr(1, __pa(pgd0) + TTBR1_OFFSET);
> +	local_flush_tlb_all();
> +}
> +
> +#else
> +
> +void __init early_paging_init(const struct machine_desc *mdesc,
> +			      struct proc_info_list *procinfo)
> +{
> +	if (mdesc->init_meminfo)
> +		mdesc->init_meminfo();
> +}
> +
> +#endif
> +
>  /*
>   * paging_init() sets up the page tables, initialises the zone memory
>   * maps, and sets up the zero page, bad page and bad page tables.
> -- 
> 1.7.9.5
>