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From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <kasan-dev@googlegroups.com>,
<linux-mm@kvack.org>
Subject: Re: [PATCH v2 1/3] vmalloc: Choose a better start address in vm_area_register_early()
Date: Thu, 5 Aug 2021 20:46:20 +0800 [thread overview]
Message-ID: <d2280ab3-2c31-7525-b03d-b4717273b2c3@huawei.com> (raw)
In-Reply-To: <20210804111402.GB4857@arm.com>
On 2021/8/4 19:14, Catalin Marinas wrote:
> On Mon, Aug 02, 2021 at 10:39:04AM +0800, Kefeng Wang wrote:
>> On 2021/8/1 23:23, Catalin Marinas wrote:
>>> On Tue, Jul 20, 2021 at 10:51:03AM +0800, Kefeng Wang wrote:
>>>> There are some fixed locations in the vmalloc area be reserved
>>>> in ARM(see iotable_init()) and ARM64(see map_kernel()), but for
>>>> pcpu_page_first_chunk(), it calls vm_area_register_early() and
>>>> choose VMALLOC_START as the start address of vmap area which
>>>> could be conflicted with above address, then could trigger a
>>>> BUG_ON in vm_area_add_early().
>>>>
>>>> Let's choose the end of existing address range in vmlist as the
>>>> start address instead of VMALLOC_START to avoid the BUG_ON.
>>>>
>>>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>>>> ---
>>>> mm/vmalloc.c | 8 +++++---
>>>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>>>> index d5cd52805149..a98cf97f032f 100644
>>>> --- a/mm/vmalloc.c
>>>> +++ b/mm/vmalloc.c
>>>> @@ -2238,12 +2238,14 @@ void __init vm_area_add_early(struct vm_struct *vm)
>>>> */
>>>> void __init vm_area_register_early(struct vm_struct *vm, size_t align)
>>>> {
>>>> - static size_t vm_init_off __initdata;
>>>> + unsigned long vm_start = VMALLOC_START;
>>>> + struct vm_struct *tmp;
>>>> unsigned long addr;
>>>> - addr = ALIGN(VMALLOC_START + vm_init_off, align);
>>>> - vm_init_off = PFN_ALIGN(addr + vm->size) - VMALLOC_START;
>>>> + for (tmp = vmlist; tmp; tmp = tmp->next)
>>>> + vm_start = (unsigned long)tmp->addr + tmp->size;
>>>> + addr = ALIGN(vm_start, align);
>>>> vm->addr = (void *)addr;
>>>> vm_area_add_early(vm);
>>> Is there a risk of breaking other architectures? It doesn't look like to
>>> me but I thought I'd ask.
>> Before this patch, vm_init_off is to record the offset from VMALLOC_START,
>>
>> but it use VMALLOC_START as start address on the function
>> vm_area_register_early()
>>
>> called firstly, this will cause the BUG_ON.
>>
>> With this patch, the most important change is that we choose the start
>> address via
>>
>> dynamic calculate the 'start' address by traversing the list.
>>
>> [wkf@localhost linux-next]$ git grep vm_area_register_early
>> arch/alpha/mm/init.c: vm_area_register_early(&console_remap_vm, PAGE_SIZE);
>> arch/x86/xen/p2m.c: vm_area_register_early(&vm, PMD_SIZE *
>> PMDS_PER_MID_PAGE);
>> mm/percpu.c: vm_area_register_early(&vm, PAGE_SIZE);
>> [wkf@localhost linux-next]$ git grep vm_area_add_early
>> arch/arm/mm/ioremap.c: vm_area_add_early(vm);
>> arch/arm64/mm/mmu.c: vm_area_add_early(vma);
>>
>> x86/alpha won't call vm_area_add_early(), only arm64 could call both vm_area_add_early()
>> and vm_area_register_early() when this patchset is merged. so it won't break other architectures.
> Thanks for checking.
>
>>> Also, instead of always picking the end, could we search for a range
>>> that fits?
>> We only need a space in vmalloc range, using end or a range in the middle
>> is not different.
> I was thinking of making it more future-proof in case one registers a
> vm area towards the end of the range. It's fairly easy to pick a range
> in the middle now that you are adding a list traversal.
ok, will chose a suitable hole in the vmalloc range.
>
next prev parent reply other threads:[~2021-08-05 12:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-20 2:51 [PATCH v2 0/3] arm64: support page mapping percpu first chunk allocator Kefeng Wang
2021-07-20 2:51 ` [PATCH v2 1/3] vmalloc: Choose a better start address in vm_area_register_early() Kefeng Wang
2021-08-01 15:23 ` Catalin Marinas
2021-08-02 2:39 ` Kefeng Wang
2021-08-04 11:14 ` Catalin Marinas
2021-08-05 12:46 ` Kefeng Wang [this message]
2021-07-20 2:51 ` [PATCH v2 2/3] arm64: Support page mapping percpu first chunk allocator Kefeng Wang
2021-08-01 15:53 ` Catalin Marinas
2021-08-02 2:47 ` Kefeng Wang
2021-07-20 2:51 ` [PATCH v2 3/3] kasan: arm64: Fix pcpu_page_first_chunk crash with KASAN_VMALLOC Kefeng Wang
2021-07-22 11:00 ` Marco Elver
2021-07-22 12:14 ` Kefeng Wang
2021-07-26 1:19 ` [PATCH v2 0/3] arm64: support page mapping percpu first chunk allocator Kefeng Wang
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