Separate generic header usage from ARCH_MULTIPLATFORM

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.

Quoted 10 lines · 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.

Quoted 5 lines

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.

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.

Arnd

commit b62a2b6e472bfb3c7b224b300f25365112be1ea9

Author: Arnd Bergmann <[email protected]>
Date:   Mon Jun 3 11:06:23 2013 +0200

ARM: make "randconfig" work with NOMMU

Signed-off-by Arnd Bergmann <[email protected]>

arch/arm/Kconfig +4 -5

index bbe5b2a..25763ce 100644
@@ -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

arch/arm/include/asm/cacheflush.h +1 -1

index bff7138..ba960e5 100644
@@ -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) \

arch/arm/include/asm/io.h +4 -0

index 56752a6..b6821ab 100644
@@ -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

arch/arm/include/asm/mach/map.h +2 -1

index 2fe141f..d380191 100644
@@ -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

arch/arm/kernel/debug.S +1 -1

index a0a0efe..748c269 100644
@@ -35,7 +35,7 @@
 
  #else /* !CONFIG_MMU */
                 .macro  addruart_current, rx, tmp1, tmp2
-               addruart        \rx, \tmp1
+               addruart        \rx, \tmp1, \tmp2
                 .endm
 
  #endif /* CONFIG_MMU */

arch/arm/kernel/head-common.S +2 -0

index 5b391a6..b5f304e 100644
@@ -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

arch/arm/kernel/suspend.c +7 -2

index c59c97e..ebfcb44 100644
@@ -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;
  }

arch/arm/mach-at91/Kconfig.non_dt +1 -0

index 6cd554a..ab8d2ce 100644
@@ -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

arch/arm/mach-imx/Kconfig +1 -1

index a7d1910..fbfb1eb 100644
@@ -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

arch/arm/mach-imx/pm-imx5.c +2 -0

index 82e79c6..3b98409e6 100644
@@ -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 */

arch/arm/mach-omap2/Kconfig +1 -1

index 18cc48b..d29727b 100644
@@ -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

arch/arm/mach-omap2/omap-secure.c +2 -2

index b970440..98624fe 100644
@@ -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;
  }

arch/arm/mach-picoxcell/Kconfig +1 -1

index 13bae78..dc98377 100644
@@ -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

arch/arm/mm/Kconfig +2 -2

index 9e8101e..3397d05 100644
@@ -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

arch/arm/plat-omap/sram.c +4 -0

index a5bc92d..ad4d277 100644
@@ -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;

drivers/iommu/Kconfig +1 -1

index c332fb9..adaf609 100644
@@ -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

drivers/staging/android/Kconfig +1 -0

index c0c95be..85fc94b 100644
@@ -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,

drivers/staging/zsmalloc/Kconfig +1 -0

index 7fab032..0ae13cd 100644
@@ -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

include/linux/kernel.h +7 -3

index cf23b15..9cc4d43 100644
@@ -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;

include/linux/mm.h +4 -0

index b87681a..5511a1c 100644
@@ -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 *);
 

mm/nommu.c +1 -0

index ecd1f15..a7709f1 100644
@@ -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;

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...)

Quoted 5 lines

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!

Quoted 4 lines

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!

I am somewhat annoyed by the fact that I had to disable ARCH_MULTIPLATFORM for !MMU kernels in order to get 'make randconfig' to work and I would rather allow it and fix the bugs.

Quoted 5 lines · On Friday 07 June 2013 16:00:47 Arnd Bergmann wrote:

Quoted 4 lines

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!

Quoted 3 lines

I am somewhat annoyed by the fact that I had to disable ARCH_MULTIPLATFORM for !MMU kernels in order to get 'make randconfig' to work and I would rather allow it and fix the bugs.

To expand on this a bit more: I want to eventually make ARCH_MULTIPLATFORM mandatory for all modern platforms, in particular anything ARMv6 and ARMv7 based. Forcing all !MMU-kernels to be !ARCH_MULTIPLATFORM means we won't get there unless we disallow !MMU on modern platforms.

Arnd

Thanks for the expansion. I like that as an aim :). We should remember it'll still only make sense for platforms where PHYS_OFFSET/DRAM_BASE is the same - not sure how many that will be.

I've had a play with keeping !MMU and ARCH_MULTIPLATFORM selectable together, and of the fixes in your diff, only the following is required to get R7 booting on top of Vexpress:

-----8<-------

arch/arm/Kconfig +1 -3

index a7f066e..ead2b25 100644
@@ -289,8 +289,7 @@ choice
 
  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
----->8--------

It's nice too, because we don't need to add back Makefile.boot for vexpress.

The R7 support, nommu-fixes and MPU patches I sent before and which I hope to have merged for 3.11 (pull request for rmk coming shortly) can all work fine using this instead of the NEED_NO_MACH_HEADERS series (IE this series)....

It would be cool, then, to have the small patch above in for 3.11 too if we're not too late and if nobody is against going down this route?

Arnd: would you like to send it as a patch to the list for consideration, or shall I take this on?

On Friday 07 June 2013 17:51:07 Jonathan Austin wrote:

Please send a patch with a correct description.