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Subject[PATCH] arm64: mm: Fix initialisation of DMA zones on non-NUMA systems
Date
John reports that the recently merged commit 1a8e1cef7603 ("arm64: use
both ZONE_DMA and ZONE_DMA32") breaks the boot on his DB845C board:

| Booting Linux on physical CPU 0x0000000000 [0x517f803c]
| Linux version 5.4.0-mainline-10675-g957a03b9e38f
| Machine model: Thundercomm Dragonboard 845c
| [...]
| Built 1 zonelists, mobility grouping on. Total pages: -188245
| Kernel command line: earlycon
| firmware_class.path=/vendor/firmware/ androidboot.hardware=db845c
| init=/init androidboot.boot_devices=soc/1d84000.ufshc
| printk.devkmsg=on buildvariant=userdebug root=/dev/sda2
| androidboot.bootdevice=1d84000.ufshc androidboot.serialno=c4e1189c
| androidboot.baseband=sda
| msm_drm.dsi_display0=dsi_lt9611_1080_video_display:
| androidboot.slot_suffix=_a skip_initramfs rootwait ro init=/init
|
| <hangs indefinitely here>

This is because, when CONFIG_NUMA=n, zone_sizes_init() fails to handle
memblocks that fall entirely within the ZONE_DMA region and erroneously ends up
trying to add a negatively-sized region into the following ZONE_DMA32, which is
later interpreted as a large unsigned region by the core MM code.

Rework the non-NUMA implementation of zone_sizes_init() so that the start
address of the memblock being processed is adjusted according to the end of the
previous zone, which is then range-checked before updating the hole information
of subsequent zones.

Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/lkml/CALAqxLVVcsmFrDKLRGRq7GewcW405yTOxG=KR3csVzQ6bXutkA@mail.gmail.com
Fixes: 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32")
Reported-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/mm/init.c | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)

Compile-tested only.

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index be9481cdf3b9..b65dffdfb201 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -214,15 +214,14 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
{
struct memblock_region *reg;
unsigned long zone_size[MAX_NR_ZONES], zhole_size[MAX_NR_ZONES];
- unsigned long max_dma32 = min;
- unsigned long __maybe_unused max_dma = min;
+ unsigned long __maybe_unused max_dma, max_dma32;

memset(zone_size, 0, sizeof(zone_size));

+ max_dma = max_dma32 = min;
#ifdef CONFIG_ZONE_DMA
- max_dma = PFN_DOWN(arm64_dma_phys_limit);
+ max_dma = max_dma32 = PFN_DOWN(arm64_dma_phys_limit);
zone_size[ZONE_DMA] = max_dma - min;
- max_dma32 = max_dma;
#endif
#ifdef CONFIG_ZONE_DMA32
max_dma32 = PFN_DOWN(arm64_dma32_phys_limit);
@@ -236,25 +235,23 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
unsigned long start = memblock_region_memory_base_pfn(reg);
unsigned long end = memblock_region_memory_end_pfn(reg);

- if (start >= max)
- continue;
#ifdef CONFIG_ZONE_DMA
- if (start < max_dma) {
- unsigned long dma_end = min_not_zero(end, max_dma);
+ if (start >= min && start < max_dma) {
+ unsigned long dma_end = min(end, max_dma);
zhole_size[ZONE_DMA] -= dma_end - start;
+ start = dma_end;
}
#endif
#ifdef CONFIG_ZONE_DMA32
- if (start < max_dma32) {
+ if (start >= max_dma && start < max_dma32) {
unsigned long dma32_end = min(end, max_dma32);
- unsigned long dma32_start = max(start, max_dma);
- zhole_size[ZONE_DMA32] -= dma32_end - dma32_start;
+ zhole_size[ZONE_DMA32] -= dma32_end - start;
+ start = dma32_end;
}
#endif
- if (end > max_dma32) {
+ if (start >= max_dma32 && start < max) {
unsigned long normal_end = min(end, max);
- unsigned long normal_start = max(start, max_dma32);
- zhole_size[ZONE_NORMAL] -= normal_end - normal_start;
+ zhole_size[ZONE_NORMAL] -= normal_end - start;
}
}

--
2.17.1
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