[PATCH v3 0/3] Separate generic header usage from ARCH_MULTIPLATFORM

Jonathan Austin jonathan.austin at arm.com
Fri Jun 7 09:13:24 EDT 2013


Hi Arnd,

On 07/06/13 13:36, Arnd Bergmann wrote:
> On Friday 07 June 2013 11:48:28 Jonathan Austin wrote:
>> The original aim of this series was to restore the ability to build a NOMMU
>> kernel for Versatile Express, something that was lost when we converted
>> ARCH_VEXPRESS for ARCH_MULTIPLATFORM.
>>
>> In order to do this, it is necessary to abstract the use of generic headers
>> from selection of ARCH_MULTIPLATFORM so that the two can be used separately.
>> This is necessary becuase building a multiplatform kernel for processors
>> without and MMU doesn't make sense (it is necessary to hardcode certain mem-map
>> related data) and the versatile express can host NOMMU processors.
>>
>> This series performs this separation, and then goes on to add a 'dummy'
>> ARCH_VEXPRESS_NOMMU platform that can be selected as standalone platform.
>>
>> Patch 2 was sent to the list as an RFC some time ago where it was ACKd, but
>> alone is not sufficient to solve the problem, hence this follow-up series.
>
> I'd like to revisit whether we can't just make !CONFIG_MMU work in combination
> with CONFIG_ARCH_MULTIPLATFORM.

Do you mean you want to build real !MMU multiplatform kernels that 
validly work on multiple platforms, or are you just interested in 
keeping the config options set?

I don't think the former makes sense - we still rely on setting 
CONFIG_DRAM_BASE (and hence PHYS_OFFSET) and we *can't* use the high 
exception vector on many platforms (high exception vectors is deprecated 
for R class, too) but we need to use it on others.

In the case that you just want to keep the config option set, I don't 
really see what you gain?

The problem I see with enabling !MMU/ARCH_MULTIPLATFORM is that you end 
up needing to change platforms that (as far as I know) people never use 
in NOMMU configurations for NOMMU behaviour: cf imx, omap2 needing to be 
changed in a specific way for the NOMMU case in the diff below. (I say 
'specific way' because, of course, this series does make a small change 
to them, but I see it more as separating out two previously conflated 
options than as NOMMU specific changes...)

> I've spent some time recently on randconfig
> builds and used the patch below to actually fix all build-time bugs I see
> with that. The changes need to be split up into separate patches and reviewed
> one by one, but I think the only one you really need is to not select
> ARM_PATCH_PHYS_VIRT when building a NOMMU kernel.

I agree that this seems to get you to something that builds, though I'm 
not sure it'd build something that runs... Don't we end up just making 
life harder (I think the diff below is more complicated than the one for 
this series...) for ourselves without a win?

Doesn't the explicit dependency of CONFIG_MMU for ARCH_MULTIPLATFORM 
mean that randconfig builds still work, even without the changes below?

Apologies if I'm missing a use-case here!

Jonny

>
>          Arnd
>
> commit b62a2b6e472bfb3c7b224b300f25365112be1ea9
> Author: Arnd Bergmann <arnd at arndb.de>
> Date:   Mon Jun 3 11:06:23 2013 +0200
>
>      ARM: make "randconfig" work with NOMMU
>
>      Signed-off-by: Arnd Bergmann <arnd at arndb.de>
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index bbe5b2a..25763ce 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -19,7 +19,7 @@ config ARM
>          select GENERIC_STRNCPY_FROM_USER
>          select GENERIC_STRNLEN_USER
>          select HARDIRQS_SW_RESEND
> -       select HAVE_AOUT
> +       select HAVE_AOUT if MMU
>          select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
>          select HAVE_ARCH_KGDB
>          select HAVE_ARCH_SECCOMP_FILTER
> @@ -285,13 +285,11 @@ config MMU
>   #
>   choice
>          prompt "ARM system type"
> -       default ARCH_VERSATILE if !MMU
> -       default ARCH_MULTIPLATFORM if MMU
> +       default ARCH_MULTIPLATFORM
>
>   config ARCH_MULTIPLATFORM
>          bool "Allow multiple platforms to be selected"
> -       depends on MMU
> -       select ARM_PATCH_PHYS_VIRT
> +       select ARM_PATCH_PHYS_VIRT if MMU
>          select AUTO_ZRELADDR
>          select COMMON_CLK
>          select MULTI_IRQ_HANDLER
> @@ -1812,6 +1810,7 @@ config XEN
>          depends on ARM && AEABI && OF
>          depends on CPU_V7 && !CPU_V6
>          depends on !GENERIC_ATOMIC64
> +       depends on MMU
>          select ARM_PSCI
>          select PARAVIRT
>          help
> diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
> index bff7138..ba960e5 100644
> --- a/arch/arm/include/asm/cacheflush.h
> +++ b/arch/arm/include/asm/cacheflush.h
> @@ -248,7 +248,7 @@ vivt_flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsig
>          }
>   }
>
> -#ifndef CONFIG_CPU_CACHE_VIPT
> +#if !defined(CONFIG_CPU_CACHE_VIPT) || !defined(CONFIG_MMU)
>   #define flush_cache_mm(mm) \
>                  vivt_flush_cache_mm(mm)
>   #define flush_cache_range(vma,start,end) \
> diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
> index 56752a6..b6821ab 100644
> --- a/arch/arm/include/asm/io.h
> +++ b/arch/arm/include/asm/io.h
> @@ -166,7 +166,11 @@ static inline void __iomem *__typesafe_io(unsigned long addr)
>   /* PCI fixed i/o mapping */
>   #define PCI_IO_VIRT_BASE       0xfee00000
>
> +#ifdef CONFIG_MMU
>   extern int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr);
> +#else
> +static inline int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr) { return 0; }
> +#endif
>
>   /*
>    * Now, pick up the machine-defined IO definitions
> diff --git a/arch/arm/include/asm/mach/map.h b/arch/arm/include/asm/mach/map.h
> index 2fe141f..d380191 100644
> --- a/arch/arm/include/asm/mach/map.h
> +++ b/arch/arm/include/asm/mach/map.h
> @@ -55,8 +55,9 @@ extern const struct mem_type *get_mem_type(unsigned int type);
>   extern int ioremap_page(unsigned long virt, unsigned long phys,
>                          const struct mem_type *mtype);
>   #else
> -#define iotable_init(map,num)  do { } while (0)
> +#define iotable_init(map,num)  do { (void)(map); } while (0)
>   #define vm_reserve_area_early(a,s,c)   do { } while (0)
> +static inline void debug_ll_io_init(void) {}
>   #endif
>
>   #endif
> diff --git a/arch/arm/kernel/debug.S b/arch/arm/kernel/debug.S
> index a0a0efe..748c269 100644
> --- a/arch/arm/kernel/debug.S
> +++ b/arch/arm/kernel/debug.S
> @@ -35,7 +35,7 @@
>
>   #else /* !CONFIG_MMU */
>                  .macro  addruart_current, rx, tmp1, tmp2
> -               addruart        \rx, \tmp1
> +               addruart        \rx, \tmp1, \tmp2
>                  .endm
>
>   #endif /* CONFIG_MMU */
> diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
> index 5b391a6..b5f304e 100644
> --- a/arch/arm/kernel/head-common.S
> +++ b/arch/arm/kernel/head-common.S
> @@ -175,6 +175,8 @@ __lookup_processor_type_data:
>          .long   __proc_info_end
>          .size   __lookup_processor_type_data, . - __lookup_processor_type_data
>
> +       __HEAD
> +
>   __error_p:
>   #ifdef CONFIG_DEBUG_LL
>          adr     r0, str_p1
> diff --git a/arch/arm/kernel/suspend.c b/arch/arm/kernel/suspend.c
> index c59c97e..ebfcb44 100644
> --- a/arch/arm/kernel/suspend.c
> +++ b/arch/arm/kernel/suspend.c
> @@ -22,7 +22,9 @@ void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr)
>          *save_ptr = virt_to_phys(ptr);
>
>          /* This must correspond to the LDM in cpu_resume() assembly */
> +#ifdef CONFIG_MMU
>          *ptr++ = virt_to_phys(idmap_pgd);
> +#endif
>          *ptr++ = sp;
>          *ptr++ = virt_to_phys(cpu_do_resume);
>
> @@ -53,11 +55,11 @@ void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr)
>    */
>   int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
>   {
> -       struct mm_struct *mm = current->active_mm;
>          int ret;
> -
> +#ifdef CONFIG_MMU
>          if (!idmap_pgd)
>                  return -EINVAL;
> +#endif
>
>          /*
>           * Provide a temporary page table with an identity mapping for
> @@ -66,11 +68,14 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
>           * back to the correct page tables.
>           */
>          ret = __cpu_suspend(arg, fn);
> +#ifdef CONFIG_MMU
>          if (ret == 0) {
> +               struct mm_struct *mm = current->active_mm;
>                  cpu_switch_mm(mm->pgd, mm);
>                  local_flush_bp_all();
>                  local_flush_tlb_all();
>          }
> +#endif
>
>          return ret;
>   }
> diff --git a/arch/arm/mach-at91/Kconfig.non_dt b/arch/arm/mach-at91/Kconfig.non_dt
> index 6cd554a..ab8d2ce 100644
> --- a/arch/arm/mach-at91/Kconfig.non_dt
> +++ b/arch/arm/mach-at91/Kconfig.non_dt
> @@ -36,6 +36,7 @@ config ARCH_AT91SAM9G45
>   config ARCH_AT91X40
>          bool "AT91x40"
>          depends on !MMU
> +       select CPU_ARM9TDMI
>          select ARCH_USES_GETTIMEOFFSET
>          select MULTI_IRQ_HANDLER
>          select SPARSE_IRQ
> diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
> index a7d1910..fbfb1eb 100644
> --- a/arch/arm/mach-imx/Kconfig
> +++ b/arch/arm/mach-imx/Kconfig
> @@ -1,7 +1,7 @@
>   config ARCH_MXC
>          bool "Freescale i.MX family" if ARCH_MULTI_V4_V5 || ARCH_MULTI_V6_V7
>          select ARCH_REQUIRE_GPIOLIB
> -       select ARM_PATCH_PHYS_VIRT
> +       select ARM_PATCH_PHYS_VIRT if MMU
>          select AUTO_ZRELADDR if !ZBOOT_ROM
>          select CLKDEV_LOOKUP
>          select CLKSRC_MMIO
> diff --git a/arch/arm/mach-imx/pm-imx5.c b/arch/arm/mach-imx/pm-imx5.c
> index 82e79c6..3b98409e6 100644
> --- a/arch/arm/mach-imx/pm-imx5.c
> +++ b/arch/arm/mach-imx/pm-imx5.c
> @@ -110,7 +110,9 @@ static int mx5_suspend_enter(suspend_state_t state)
>          }
>
>          if (state == PM_SUSPEND_MEM) {
> +#ifdef CONFIG_MMU
>                  local_flush_tlb_all();
> +#endif
>                  flush_cache_all();
>
>                  /*clear the EMPGC0/1 bits */
> diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
> index 18cc48b..d29727b 100644
> --- a/arch/arm/mach-omap2/Kconfig
> +++ b/arch/arm/mach-omap2/Kconfig
> @@ -100,7 +100,7 @@ config ARCH_OMAP2PLUS_TYPICAL
>          bool "Typical OMAP configuration"
>          default y
>          select AEABI
> -       select HIGHMEM
> +       select HIGHMEM if MMU
>          select I2C
>          select I2C_OMAP
>          select MENELAUS if ARCH_OMAP2
> diff --git a/arch/arm/mach-omap2/omap-secure.c b/arch/arm/mach-omap2/omap-secure.c
> index b970440..98624fe 100644
> --- a/arch/arm/mach-omap2/omap-secure.c
> +++ b/arch/arm/mach-omap2/omap-secure.c
> @@ -60,8 +60,8 @@ int __init omap_secure_ram_reserve_memblock(void)
>   {
>          u32 size = OMAP_SECURE_RAM_STORAGE;
>
> -       size = ALIGN(size, SECTION_SIZE);
> -       omap_secure_memblock_base = arm_memblock_steal(size, SECTION_SIZE);
> +       size = ALIGN(size, SZ_1M);
> +       omap_secure_memblock_base = arm_memblock_steal(size, SZ_1M);
>
>          return 0;
>   }
> diff --git a/arch/arm/mach-picoxcell/Kconfig b/arch/arm/mach-picoxcell/Kconfig
> index 13bae78..dc98377 100644
> --- a/arch/arm/mach-picoxcell/Kconfig
> +++ b/arch/arm/mach-picoxcell/Kconfig
> @@ -1,7 +1,7 @@
>   config ARCH_PICOXCELL
>          bool "Picochip PicoXcell" if ARCH_MULTI_V6
>          select ARCH_REQUIRE_GPIOLIB
> -       select ARM_PATCH_PHYS_VIRT
> +       select ARM_PATCH_PHYS_VIRT if MMU
>          select ARM_VIC
>          select CPU_V6K
>          select DW_APB_TIMER
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index 9e8101e..3397d05 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -6,7 +6,7 @@ comment "Processor Type"
>
>   # ARM7TDMI
>   config CPU_ARM7TDMI
> -       bool "Support ARM7TDMI processor"
> +       bool
>          depends on !MMU
>          select CPU_32v4T
>          select CPU_ABRT_LV4T
> @@ -56,7 +56,7 @@ config CPU_ARM740T
>
>   # ARM9TDMI
>   config CPU_ARM9TDMI
> -       bool "Support ARM9TDMI processor"
> +       bool
>          depends on !MMU
>          select CPU_32v4T
>          select CPU_ABRT_NOMMU
> diff --git a/arch/arm/plat-omap/sram.c b/arch/arm/plat-omap/sram.c
> index a5bc92d..ad4d277 100644
> --- a/arch/arm/plat-omap/sram.c
> +++ b/arch/arm/plat-omap/sram.c
> @@ -81,7 +81,11 @@ void __init omap_map_sram(unsigned long start, unsigned long size,
>          start = ROUND_DOWN(start, PAGE_SIZE);
>          omap_sram_size = size;
>          omap_sram_skip = skip;
> +#ifdef CONFIG_MMU
>          omap_sram_base = __arm_ioremap_exec(start, size, cached);
> +#else
> +       omap_sram_base = (void __iomem *)start;
> +#endif
>          if (!omap_sram_base) {
>                  pr_err("SRAM: Could not map\n");
>                  return;
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index c332fb9..adaf609 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -130,7 +130,7 @@ config IRQ_REMAP
>   # OMAP IOMMU support
>   config OMAP_IOMMU
>          bool "OMAP IOMMU Support"
> -       depends on ARCH_OMAP2PLUS
> +       depends on ARCH_OMAP2PLUS && MMU
>          select IOMMU_API
>
>   config OMAP_IOVMM
> diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
> index c0c95be..85fc94b 100644
> --- a/drivers/staging/android/Kconfig
> +++ b/drivers/staging/android/Kconfig
> @@ -10,6 +10,7 @@ if ANDROID
>
>   config ANDROID_BINDER_IPC
>          bool "Android Binder IPC Driver"
> +       depends on MMU
>          default n
>          ---help---
>            Binder is used in Android for both communication between processes,
> diff --git a/drivers/staging/zsmalloc/Kconfig b/drivers/staging/zsmalloc/Kconfig
> index 7fab032..0ae13cd 100644
> --- a/drivers/staging/zsmalloc/Kconfig
> +++ b/drivers/staging/zsmalloc/Kconfig
> @@ -1,5 +1,6 @@
>   config ZSMALLOC
>          bool "Memory allocator for compressed pages"
> +       depends on MMU
>          default n
>          help
>            zsmalloc is a slab-based memory allocator designed to store
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index cf23b15..9cc4d43 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -193,13 +193,17 @@ extern int _cond_resched(void);
>                  (__x < 0) ? -__x : __x;         \
>          })
>
> -#ifdef CONFIG_PROVE_LOCKING
> -void might_fault(void);
> -#else
> +#ifndef CONFIG_MMU
> +static inline void might_fault(void)
> +{
> +}
> +#elif !defined(CONFIG_PROVE_LOCKING)
>   static inline void might_fault(void)
>   {
>          might_sleep();
>   }
> +#else
> +void might_fault(void);
>   #endif
>
>   extern struct atomic_notifier_head panic_notifier_list;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index b87681a..5511a1c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -919,7 +919,11 @@ extern bool skip_free_areas_node(unsigned int flags, int nid);
>
>   int shmem_zero_setup(struct vm_area_struct *);
>
> +#ifdef CONFIG_MMU
>   extern int can_do_mlock(void);
> +#else
> +static inline int can_do_mlock(void) { return 0; }
> +#endif
>   extern int user_shm_lock(size_t, struct user_struct *);
>   extern void user_shm_unlock(size_t, struct user_struct *);
>
> diff --git a/mm/nommu.c b/mm/nommu.c
> index ecd1f15..a7709f1 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -54,6 +54,7 @@
>   #endif
>
>   void *high_memory;
> +EXPORT_SYMBOL(high_memory);
>   struct page *mem_map;
>   unsigned long max_mapnr;
>   unsigned long highest_memmap_pfn;
>
>
>





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