Re: Linux-next-20200302: arm64 build failed

Anshuman Khandual
2020-03-04T02:26:49Z

On 03/03/2020 09:58 PM, Catalin Marinas wrote:
> On Tue, Mar 03, 2020 at 09:34:45AM +0530, Anshuman Khandual wrote:
>> On 03/02/2020 11:15 PM, Catalin Marinas wrote:
>>> On Mon, Mar 02, 2020 at 03:54:43PM +0200, Mike Rapoport wrote:
>>>> On Mon, Mar 02, 2020 at 10:47:27AM +0000, Will Deacon wrote:
>>>>> [+Anshuman and Catalin]
>>>>>
>>>>> On Mon, Mar 02, 2020 at 01:58:26PM +0530, Naresh Kamboju wrote:
>>>>>> Linux-Next 20200302 arm64 build failed due to below errors,
>>>>>> Suspecting patch causing this build break.
>>>>>>
>>>>>> 87d900aef3e2 arm/arm64: add support for folded p4d page tables
>>>>>>
>>>>>> Error log,
>>>>>> -------------
>>>>>> arch/arm64/mm/mmu.c: In function 'unmap_hotplug_pud_range':
>>>>>> include/linux/compiler.h:284:1: error: incompatible type for argument
>>>>>> 1 of 'p4d_page_paddr'
>>>>>> ({ \
>>>>>> ^
>>>>>> arch/arm64/include/asm/memory.h:270:45: note: in definition of macro
>>>>>> '__phys_to_virt'
>>>>>> #define __phys_to_virt(x) ((unsigned long)((x) - physvirt_offset))
>>>>>> ^
>>>>>> arch/arm64/include/asm/pgtable.h:629:42: note: in expansion of macro '__va'
>>>>>> #define pud_offset(dir, addr) ((pud_t *)__va(pud_offset_phys((dir), (addr))))
>>>>>> ^~~~
>>>>>> include/linux/compiler.h:293:22: note: in expansion of macro '__READ_ONCE'
>>>>>> #define READ_ONCE(x) __READ_ONCE(x, 1)
>>>>>> ^~~~~~~~~~~
>>>>>> arch/arm64/include/asm/pgtable.h:628:52: note: in expansion of macro 'READ_ONCE'
>>>>>> #define pud_offset_phys(dir, addr) (p4d_page_paddr(READ_ONCE(*(dir)))
>>>>>> + pud_index(addr) * sizeof(pud_t))
>>>>>> ^~~~~~~~~
>>>>>> arch/arm64/include/asm/pgtable.h:629:47: note: in expansion of macro
>>>>>> 'pud_offset_phys'
>>>>>> #define pud_offset(dir, addr) ((pud_t *)__va(pud_offset_phys((dir), (addr))))
>>>>>> ^~~~~~~~~~~~~~~
>>>>>> arch/arm64/mm/mmu.c:827:10: note: in expansion of macro 'pud_offset'
>>>>>> pudp = pud_offset(pgdp, addr);
>>>>>> ^~~~~~~~~~
>>>>>
>>>>> Looks like we need an implementation of unmap_hotplug_p4d_range() to
>>>>> walk the dummy p4d level. Unfortunately, we don't have the folded p4d
>>>>> patches in the arm64 tree so we'll either need a common branch or the
>>>>> hotplug patches will need to be dropped for the moment.
>>>>
>>>> unmap_hotplug_p4d_range() is easy :)
>>>>
>>>> From c7a5d08ff51ca2057b6b0289c4423bdfd7643518 Mon Sep 17 00:00:00 2001
>>>> From: Mike Rapoport <rppt@linux.ibm.com>
>>>> Date: Mon, 2 Mar 2020 15:53:17 +0200
>>>> Subject: [PATCH] arm64/mm: implement unmap_hotplug_p4d_range
>>>>
>>>> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
>>>> ---
>>>> arch/arm64/mm/mmu.c | 20 +++++++++++++++++++-
>>>> 1 file changed, 19 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>>> index 05ec8e5f1436..c76b11577558 100644
>>>> --- a/arch/arm64/mm/mmu.c
>>>> +++ b/arch/arm64/mm/mmu.c
>>>> @@ -840,6 +840,24 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
>>>> } while (addr = next, addr < end);
>>>> }
>>>>
>>>> +static void unmap_hotplug_p4d_range(pgd_t *pgd, unsigned long addr,
>>>> + unsigned long end, bool free_mapped)
>>>> +{
>>>> + unsigned long next;
>>>> + pgd_t *p4dp, p4d;
>>>> +
>>>> + do {
>>>> + next = p4d_addr_end(addr, end);
>>>> + p4dp = p4d_offset(pgd, addr);
>>>> + p4d = READ_ONCE(*p4dp);
>>>> + if (p4d_none(p4d))
>>>> + continue;
>>>> +
>>>> + WARN_ON(!p4d_present(p4d));
>>>> + unmap_hotplug_pud_range(p4dp, addr, next, free_mapped);
>>>> + } while (addr = next, addr < end);
>>>> +}
>>>> +
>>>> static void unmap_hotplug_range(unsigned long addr, unsigned long end,
>>>> bool free_mapped)
>>>> {
>>>> @@ -854,7 +872,7 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end,
>>>> continue;
>>>>
>>>> WARN_ON(!pgd_present(pgd));
>>>> - unmap_hotplug_pud_range(pgdp, addr, next, free_mapped);
>>>> + unmap_hotplug_p4d_range(pgdp, addr, next, free_mapped);
>>>> } while (addr = next, addr < end);
>>>> }
>>>
>>> Thanks Mike. With the additional diff below, I can get it to build with
>>> and without the p4d clean-up patches in -next. If Anshuman confirms that
>>> they work, I can add them on top of the arm64 for-next/memory-hotremove
>>> branch.
>>
>> These two patches applied on next-20200302 works fine for hot-remove.
>
> Do they also work on top of the vanilla kernel + your hotremove patches
> (i.e. not on top of -next)?

Yes, they do work on current vanilla kernel (8b614cb8f1dcac8ca77cf4dd85f46)
and v13 hotremove series.

>
>> As the second patch also fixes the first one, IMHO both should be
>> folded into a single one instead. Just wondering if this combined
>> patch which enables P4D page table should be posted on the list or do
>> I need to respin original hot remove patches again.
>
> If your unmap patches plus the fixes from Mike and me work fine on top
> of 5.6-rc3 (as well as when combined with linux-next), I'd prefer you
Yes, they do work on both.

> respin your patches to include the p4d support from start. Otherwise, we

Okay. I will be sending V14 on v5.6-rc3 (OR v.5.6-rc4 is preferred ?) with
p4d support. I will add yours and Mike's Signed-off-by as well.

> create a single patch that Andrew can merge on top of the -mm tree.
>