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SubjectRe: [PATCH v2 2/3] arm64: Support page mapping percpu first chunk allocator
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On 2021/8/1 23:53, Catalin Marinas wrote:
> On Tue, Jul 20, 2021 at 10:51:04AM +0800, Kefeng Wang wrote:
>> Percpu embedded first chunk allocator is the firstly option, but it
>> could fails on ARM64, eg,
>> "percpu: max_distance=0x5fcfdc640000 too large for vmalloc space 0x781fefff0000"
>> "percpu: max_distance=0x600000540000 too large for vmalloc space 0x7dffb7ff0000"
>> "percpu: max_distance=0x5fff9adb0000 too large for vmalloc space 0x5dffb7ff0000"
>>
>> then we could meet "WARNING: CPU: 15 PID: 461 at vmalloc.c:3087 pcpu_get_vm_areas+0x488/0x838",
>> even the system could not boot successfully.
>>
>> Let's implement page mapping percpu first chunk allocator as a fallback
>> to the embedding allocator to increase the robustness of the system.
> It looks like x86, powerpc and sparc implement their own
> setup_per_cpu_areas(). I had a quick look on finding some commonalities
> but I think it's a lot more hassle to make a generic version out of them
> (powerpc looks the simplest though). I think we could add a generic
> variant with the arm64 support and later migrate other architectures to
> it if possible.
Ok, let's do it later, I could try to make some cleanup after the
patchset is merged ;)
> The patch looks ok to me otherwise but I'd need an ack from Greg as it
> touches drivers/.

the arch_numa is only used ARM64 and riscv, the
NEED_PER_CPU_PAGE_FIRST_CHUNK

is not enabled on RISCV, so it's no bad effect.

>
> BTW, do we need something similar for the non-NUMA
> setup_per_cpu_areas()? I can see this patch only enables
> NEED_PER_CPU_PAGE_FIRST_CHUNK if NUMA.
>
> Leaving the rest of the patch below for Greg.
>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>> arch/arm64/Kconfig | 4 ++
>> drivers/base/arch_numa.c | 82 +++++++++++++++++++++++++++++++++++-----
>> 2 files changed, 76 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index b5b13a932561..eacb5873ded1 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -1045,6 +1045,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>> def_bool y
>> depends on NUMA
>>
>> +config NEED_PER_CPU_PAGE_FIRST_CHUNK
>> + def_bool y
>> + depends on NUMA
>> +
>> source "kernel/Kconfig.hz"
>>
>> config ARCH_SPARSEMEM_ENABLE
>> diff --git a/drivers/base/arch_numa.c b/drivers/base/arch_numa.c
>> index 4cc4e117727d..563b2013b75a 100644
>> --- a/drivers/base/arch_numa.c
>> +++ b/drivers/base/arch_numa.c
>> @@ -14,6 +14,7 @@
>> #include <linux/of.h>
>>
>> #include <asm/sections.h>
>> +#include <asm/pgalloc.h>
>>
>> struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
>> EXPORT_SYMBOL(node_data);
>> @@ -168,22 +169,83 @@ static void __init pcpu_fc_free(void *ptr, size_t size)
>> memblock_free_early(__pa(ptr), size);
>> }
>>
>> +#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
>> +static void __init pcpu_populate_pte(unsigned long addr)
>> +{
>> + pgd_t *pgd = pgd_offset_k(addr);
>> + p4d_t *p4d;
>> + pud_t *pud;
>> + pmd_t *pmd;
>> +
>> + p4d = p4d_offset(pgd, addr);
>> + if (p4d_none(*p4d)) {
>> + pud_t *new;
>> +
>> + new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>> + if (!new)
>> + goto err_alloc;
>> + p4d_populate(&init_mm, p4d, new);
>> + }
>> +
>> + pud = pud_offset(p4d, addr);
>> + if (pud_none(*pud)) {
>> + pmd_t *new;
>> +
>> + new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>> + if (!new)
>> + goto err_alloc;
>> + pud_populate(&init_mm, pud, new);
>> + }
>> +
>> + pmd = pmd_offset(pud, addr);
>> + if (!pmd_present(*pmd)) {
>> + pte_t *new;
>> +
>> + new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>> + if (!new)
>> + goto err_alloc;
>> + pmd_populate_kernel(&init_mm, pmd, new);
>> + }
>> +
>> + return;
>> +
>> +err_alloc:
>> + panic("%s: Failed to allocate %lu bytes align=%lx from=%lx\n",
>> + __func__, PAGE_SIZE, PAGE_SIZE, PAGE_SIZE);
>> +}
>> +#endif
>> +
>> void __init setup_per_cpu_areas(void)
>> {
>> unsigned long delta;
>> unsigned int cpu;
>> - int rc;
>> + int rc = -EINVAL;
>> +
>> + if (pcpu_chosen_fc != PCPU_FC_PAGE) {
>> + /*
>> + * Always reserve area for module percpu variables. That's
>> + * what the legacy allocator did.
>> + */
>> + rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
>> + PERCPU_DYNAMIC_RESERVE, PAGE_SIZE,
>> + pcpu_cpu_distance,
>> + pcpu_fc_alloc, pcpu_fc_free);
>> +#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
>> + if (rc < 0)
>> + pr_warn("PERCPU: %s allocator failed (%d), falling back to page size\n",
>> + pcpu_fc_names[pcpu_chosen_fc], rc);
>> +#endif
>> + }
>>
>> - /*
>> - * Always reserve area for module percpu variables. That's
>> - * what the legacy allocator did.
>> - */
>> - rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
>> - PERCPU_DYNAMIC_RESERVE, PAGE_SIZE,
>> - pcpu_cpu_distance,
>> - pcpu_fc_alloc, pcpu_fc_free);
>> +#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
>> + if (rc < 0)
>> + rc = pcpu_page_first_chunk(PERCPU_MODULE_RESERVE,
>> + pcpu_fc_alloc,
>> + pcpu_fc_free,
>> + pcpu_populate_pte);
>> +#endif
>> if (rc < 0)
>> - panic("Failed to initialize percpu areas.");
>> + panic("Failed to initialize percpu areas (err=%d).", rc);
>>
>> delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
>> for_each_possible_cpu(cpu)
>> --
>> 2.26.2
> .
>

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