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Message-ID: <cf1a0700-4cd4-4550-c0eb-645b60cc83b4@huawei.com>
Date: Fri, 8 Jan 2021 09:09:46 +0800
From: chenzhou <chenzhou10@...wei.com>
To: Catalin Marinas <catalin.marinas@....com>,
Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
CC: <will@...nel.org>, <ardb@...nel.org>, <akpm@...ux-foundation.org>,
<rppt@...nel.org>, <song.bao.hua@...ilicon.com>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <huawei.libin@...wei.com>,
<xiexiuqi@...wei.com>
Subject: Re: [PATCH 2/2] arm64: mm: fix kdump broken with ZONE_DMA
reintroduced
On 2021/1/7 22:25, Catalin Marinas wrote:
> On Sat, Dec 26, 2020 at 11:34:58AM +0100, Nicolas Saenz Julienne wrote:
>> On Sat, 2020-12-26 at 11:35 +0800, Chen Zhou wrote:
>>> If the memory reserved for crash dump kernel falled in ZONE_DMA32,
>>> the devices in crash dump kernel need to use ZONE_DMA will alloc fail.
>>>
>>> Fix this by reserving low memory in ZONE_DMA if CONFIG_ZONE_DMA is
>>> enabled, otherwise, reserving in ZONE_DMA32.
>>>
>>> Fixes: bff3b04460a8 ("arm64: mm: reserve CMA and crashkernel in ZONE_DMA32")
>> I'm not so sure this counts as a fix, if someone backports it it'll probably
>> break things as it depends on the series that dynamically sizes DMA zones.
>>
>>> Signed-off-by: Chen Zhou <chenzhou10@...wei.com>
>>> ---
>> Why not doing the same with CMA? You'll probably have to move the
>> dma_contiguous_reserve() call into bootmem_init() so as to make sure that
>> arm64_dma_phys_limit is populated.
> Do we need the arm64_dma32_phys_limit at all? I can see the
> (arm64_dma_phys_limit ? : arm64_dma32_phys_limit) pattern in several
> places but I think we can just live with the arm64_dma_phys_limit.
Yes, arm64_dma_phys_limit is enough.
>
> Also, I don't think we need any early ARCH_LOW_ADDRESS_LIMIT. It's only
> used by memblock_alloc_low() and that's called from swiotlb_init()
> after arm64_dma_phys_limit was initialised.
>
> What about something like below (on top of you ARCH_LOW_ADDRESS_LIMIT
> fix but I can revert that)? I haven't tested it in all configurations
> yet.
>
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 69ad25fbeae4..ca2cd75d3286 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -94,8 +94,7 @@
> #endif /* CONFIG_ARM64_FORCE_52BIT */
>
> extern phys_addr_t arm64_dma_phys_limit;
> -extern phys_addr_t arm64_dma32_phys_limit;
> -#define ARCH_LOW_ADDRESS_LIMIT ((arm64_dma_phys_limit ? : arm64_dma32_phys_limit) - 1)
> +#define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit - 1)
>
> struct debug_info {
> #ifdef CONFIG_HAVE_HW_BREAKPOINT
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 7deddf56f7c3..596a94bf5ed6 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -59,7 +59,6 @@ EXPORT_SYMBOL(memstart_addr);
> * bit addressable memory area.
> */
> phys_addr_t arm64_dma_phys_limit __ro_after_init;
> -phys_addr_t arm64_dma32_phys_limit __ro_after_init;
>
> #ifdef CONFIG_KEXEC_CORE
> /*
> @@ -84,7 +83,7 @@ static void __init reserve_crashkernel(void)
>
> if (crash_base == 0) {
> /* Current arm64 boot protocol requires 2MB alignment */
> - crash_base = memblock_find_in_range(0, arm64_dma32_phys_limit,
> + crash_base = memblock_find_in_range(0, arm64_dma_phys_limit,
> crash_size, SZ_2M);
> if (crash_base == 0) {
> pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> @@ -196,6 +195,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
> unsigned long max_zone_pfns[MAX_NR_ZONES] = {0};
> unsigned int __maybe_unused acpi_zone_dma_bits;
> unsigned int __maybe_unused dt_zone_dma_bits;
> + phys_addr_t dma32_phys_limit = max_zone_phys(32);
>
> #ifdef CONFIG_ZONE_DMA
> acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
> @@ -205,8 +205,12 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
> max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
> #endif
> #ifdef CONFIG_ZONE_DMA32
> - max_zone_pfns[ZONE_DMA32] = PFN_DOWN(arm64_dma32_phys_limit);
> + max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
> + if (!arm64_dma_phys_limit)
> + arm64_dma_phys_limit = dma32_phys_limit;
> #endif
> + if (!arm64_dma_phys_limit)
> + arm64_dma_phys_limit = PHYS_MASK + 1;
> max_zone_pfns[ZONE_NORMAL] = max;
>
> free_area_init(max_zone_pfns);
> @@ -394,16 +398,9 @@ void __init arm64_memblock_init(void)
>
> early_init_fdt_scan_reserved_mem();
>
> - if (IS_ENABLED(CONFIG_ZONE_DMA32))
> - arm64_dma32_phys_limit = max_zone_phys(32);
> - else
> - arm64_dma32_phys_limit = PHYS_MASK + 1;
> -
> reserve_elfcorehdr();
>
> high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
> -
> - dma_contiguous_reserve(arm64_dma32_phys_limit);
> }
>
> void __init bootmem_init(void)
> @@ -438,6 +435,11 @@ void __init bootmem_init(void)
> sparse_init();
> zone_sizes_init(min, max);
>
> + /*
> + * Reserve the CMA area after arm64_dma_phys_limit was initialised.
> + */
> + dma_contiguous_reserve(arm64_dma_phys_limit);
> +
> /*
> * request_standard_resources() depends on crashkernel's memory being
> * reserved, so do it here.
> @@ -455,7 +457,7 @@ void __init bootmem_init(void)
> void __init mem_init(void)
> {
> if (swiotlb_force == SWIOTLB_FORCE ||
> - max_pfn > PFN_DOWN(arm64_dma_phys_limit ? : arm64_dma32_phys_limit))
> + max_pfn > PFN_DOWN(arm64_dma_phys_limit))
> swiotlb_init(1);
> else
> swiotlb_force = SWIOTLB_NO_FORCE;
> .
>
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