[1/2] arm: Cleanup sanity_check_meminfo

Commit Message

Laura Abbott Jan. 3, 2017, 8:56 p.m. UTC

The logic for sanity_check_meminfo has become difficult to
follow. Clean up the code so it's more obvious what the code
is actually trying to do. Additionally, meminfo is now removed
so rename the function to better describe it's purpose.

Originally proposed in http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/296978.html

Signed-off-by: Laura Abbott <[e-mail]>
Signed-off-by: Laura Abbott <[e-mail]>
---
 arch/arm/kernel/setup.c |  4 ++--
 arch/arm/mm/mmu.c       | 59 +++++++++++++++----------------------------------
 arch/arm/mm/nommu.c     |  8 +++----
 3 files changed, 24 insertions(+), 47 deletions(-)

Comments

Nicolas Pitre Jan. 4, 2017, 1:12 a.m. UTC | #1

On Tue, 3 Jan 2017, Laura Abbott wrote:

> 
> The logic for sanity_check_meminfo has become difficult to
> follow. Clean up the code so it's more obvious what the code
> is actually trying to do.

Absolutely. This function has a long history of subtle bugs ... and 
broken fixes.

> +		if (reg->base < vmalloc_limit) {
> +			if (block_end > arm_lowmem_limit)
> +				arm_lowmem_limit = min(
> +						(phys_addr_t)vmalloc_limit,
> +						block_end);

Just to illustrate how subtle this can be, the above would reintroduce a 
bug that was fixed in commit b9a019899f.


Nicolas

Laura Abbott Jan. 4, 2017, 4:50 p.m. UTC | #2

On 01/03/2017 05:12 PM, Nicolas Pitre wrote:
> On Tue, 3 Jan 2017, Laura Abbott wrote:
> 
>>
>> The logic for sanity_check_meminfo has become difficult to
>> follow. Clean up the code so it's more obvious what the code
>> is actually trying to do.
> 
> Absolutely. This function has a long history of subtle bugs ... and 
> broken fixes.
> 
>> +		if (reg->base < vmalloc_limit) {
>> +			if (block_end > arm_lowmem_limit)
>> +				arm_lowmem_limit = min(
>> +						(phys_addr_t)vmalloc_limit,
>> +						block_end);
> 
> Just to illustrate how subtle this can be, the above would reintroduce a 
> bug that was fixed in commit b9a019899f.
> 
> 
> Nicolas
> 

Yup, I saw that commit and thought "I need to keep the fix". And yet I
still managed to get it wrong. I'll fix in a v2.

Thanks,
Laura

Patch

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 34e3f3c..8a8051c 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -81,7 +81,7 @@  __setup("fpe=", fpe_setup);
 extern void init_default_cache_policy(unsigned long);
 extern void paging_init(const struct machine_desc *desc);
 extern void early_paging_init(const struct machine_desc *);
-extern void sanity_check_meminfo(void);
+extern void adjust_lowmem_bounds(void);
 extern enum reboot_mode reboot_mode;
 extern void setup_dma_zone(const struct machine_desc *desc);
 
@@ -1093,7 +1093,7 @@  void __init setup_arch(char **cmdline_p)
 	setup_dma_zone(mdesc);
 	xen_early_init();
 	efi_init();
-	sanity_check_meminfo();
+	adjust_lowmem_bounds();
 	arm_memblock_init(mdesc);
 
 	early_ioremap_reset();
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 4001dd1..32ecdfd 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1152,13 +1152,11 @@  early_param("vmalloc", early_vmalloc);
 
 phys_addr_t arm_lowmem_limit __initdata = 0;
 
-void __init sanity_check_meminfo(void)
+void __init adjust_lowmem_bounds(void)
 {
 	phys_addr_t memblock_limit = 0;
-	int highmem = 0;
 	u64 vmalloc_limit;
 	struct memblock_region *reg;
-	bool should_use_highmem = false;
 
 	/*
 	 * Let's use our own (unoptimized) equivalent of __pa() that is
@@ -1172,43 +1170,13 @@  void __init sanity_check_meminfo(void)
 	for_each_memblock(memory, reg) {
 		phys_addr_t block_start = reg->base;
 		phys_addr_t block_end = reg->base + reg->size;
-		phys_addr_t size_limit = reg->size;
 
-		if (reg->base >= vmalloc_limit)
-			highmem = 1;
-		else
-			size_limit = vmalloc_limit - reg->base;
 
-
-		if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
-
-			if (highmem) {
-				pr_notice("Ignoring RAM at %pa-%pa (!CONFIG_HIGHMEM)\n",
-					  &block_start, &block_end);
-				memblock_remove(reg->base, reg->size);
-				should_use_highmem = true;
-				continue;
-			}
-
-			if (reg->size > size_limit) {
-				phys_addr_t overlap_size = reg->size - size_limit;
-
-				pr_notice("Truncating RAM at %pa-%pa",
-					  &block_start, &block_end);
-				block_end = vmalloc_limit;
-				pr_cont(" to -%pa", &block_end);
-				memblock_remove(vmalloc_limit, overlap_size);
-				should_use_highmem = true;
-			}
-		}
-
-		if (!highmem) {
-			if (block_end > arm_lowmem_limit) {
-				if (reg->size > size_limit)
-					arm_lowmem_limit = vmalloc_limit;
-				else
-					arm_lowmem_limit = block_end;
-			}
+		if (reg->base < vmalloc_limit) {
+			if (block_end > arm_lowmem_limit)
+				arm_lowmem_limit = min(
+						(phys_addr_t)vmalloc_limit,
+						block_end);
 
 			/*
 			 * Find the first non-pmd-aligned page, and point
@@ -1233,9 +1201,6 @@  void __init sanity_check_meminfo(void)
 		}
 	}
 
-	if (should_use_highmem)
-		pr_notice("Consider using a HIGHMEM enabled kernel.\n");
-
 	high_memory = __va(arm_lowmem_limit - 1) + 1;
 
 	/*
@@ -1248,6 +1213,18 @@  void __init sanity_check_meminfo(void)
 	if (!memblock_limit)
 		memblock_limit = arm_lowmem_limit;
 
+	if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
+		if (memblock_end_of_DRAM() > arm_lowmem_limit) {
+			phys_addr_t end = memblock_end_of_DRAM();
+
+			pr_notice("Ignoring RAM at %pa-%pa\n",
+				  &memblock_limit, &end);
+			pr_notice("Consider using a HIGHMEM enabled kernel.\n");
+
+			memblock_remove(memblock_limit, end);
+		}
+	}
+
 	memblock_set_current_limit(memblock_limit);
 }
 
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index 2740967..13a25d6 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c
@@ -85,7 +85,7 @@  static unsigned long irbar_read(void)
 }
 
 /* MPU initialisation functions */
-void __init sanity_check_meminfo_mpu(void)
+void __init adjust_lowmem_bounds_mpu(void)
 {
 	phys_addr_t phys_offset = PHYS_OFFSET;
 	phys_addr_t aligned_region_size, specified_mem_size, rounded_mem_size;
@@ -274,7 +274,7 @@  void __init mpu_setup(void)
 	}
 }
 #else
-static void sanity_check_meminfo_mpu(void) {}
+static void adjust_lowmem_bounds_mpu(void) {}
 static void __init mpu_setup(void) {}
 #endif /* CONFIG_ARM_MPU */
 
@@ -295,10 +295,10 @@  void __init arm_mm_memblock_reserve(void)
 #endif
 }
 
-void __init sanity_check_meminfo(void)
+void __init adjust_lowmem_bounds(void)
 {
 	phys_addr_t end;
-	sanity_check_meminfo_mpu();
+	adjust_lowmem_bounds_mpu();
 	end = memblock_end_of_DRAM();
 	high_memory = __va(end - 1) + 1;
 	memblock_set_current_limit(end);