From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Anshuman Khandual <anshuman.khandual@arm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: Fwd: [Bug 213069] New: kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:147! Oops: Exception in kernel mode, sig: 5 [#1]
Date: Mon, 17 May 2021 14:59:53 +0200 [thread overview]
Message-ID: <52ab4861-3a77-14da-1179-3ea79964c950@csgroup.eu> (raw)
In-Reply-To: <6fcdf4f2-9bed-4b0f-8ed8-74cb25484ea6@arm.com>
Le 17/05/2021 à 14:49, Anshuman Khandual a écrit :
>
>
> On 5/17/21 11:25 AM, Aneesh Kumar K.V wrote:
>> On 5/17/21 11:17 AM, Christophe Leroy wrote:
>>> +aneesh
>>> +linuxppc-dev list
>>>
>>> Le 17/05/2021 à 07:44, Anshuman Khandual a écrit :
>>>> Hello Christophe,
>>>>
>>>> DEBUG_VM_PGTABLE has now been re-enabled on powerpc recently ? was not
>>>> aware about this. From the error log, it failed explicitly on 4K page
>>>> size hash config.
>>>>
>>>> static inline pmd_t hash__pmd_mkhuge(pmd_t pmd)
>>>> {
>>>> BUG(); ------> Failed
>>>> return pmd;
>>>> }
>>>>
>>>> static inline pmd_t __pmd_mkhuge(pmd_t pmd)
>>>> {
>>>> if (radix_enabled())
>>>> return radix__pmd_mkhuge(pmd);
>>>> return hash__pmd_mkhuge(pmd);
>>>> }
>>>>
>>>> pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
>>>> {
>>>> unsigned long pmdv;
>>>>
>>>> pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK;
>>>>
>>>> return __pmd_mkhuge(pmd_set_protbits(__pmd(pmdv), pgprot));
>>>> }
>>>>
>>>> It seems like on powerpc, where pfn_pmd() makes a huge page but which
>>>> is not supported on 4K hash config thus triggering the BUG(). But all
>>>> pfn_pmd() call sites inside the debug_vm_pgtable() test are protected
>>>> with CONFIG_TRANSPARENT_HUGEPAGE. IIUC unlike powerpc, pfn_pmd() does
>>>> not directly make a huge page on other platforms.
>>>>
>>>> Looking at arch/powerpc/include/asm/book3s/64/hash-4k.h, all relevant
>>>> THP helpers has BUG() or 0 which indicates THP might not be supported
>>>> on 4K page size hash config ?
>>>>
>>>> But looking at arch/powerpc/platforms/Kconfig.cputype, it seems like
>>>> HAVE_ARCH_TRANSPARENT_HUGEPAGE is invariably selected on PPC_BOOK3S_64
>>>> platforms which I assume includes 4K page size hash config as well.
>>>>
>>>> Is THP some how getting enabled on this 4K page size hash config where
>>>> it should not be (thus triggering the BUG) ? OR am I missing something
>>>> here.
>>>>
>>>
>>
>> We should put those pfn_pmd() and pfn_pud() after
>>
>> if (!has_transparent_hugepage())
>> return;
>
> The following patch has been lightly tested on arm64 and x86 platforms.
> Could you please verify if this solves the problem on powerpc 4K hash
> config ? Thank you.
No need to update pmd_advanced_tests() and pud_advanced_tests() ?
Christophe
next prev parent reply other threads:[~2021-05-17 13:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-14 23:44 [Bug 213069] New: kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:147! Oops: Exception in kernel mode, sig: 5 [#1] bugzilla-daemon
2021-05-15 10:20 ` [Bug 213069] " bugzilla-daemon
[not found] ` <4deb5cd5-c713-b020-9143-c74a031e3fd5@csgroup.eu>
[not found] ` <a8841b4e-3bff-f600-eac7-501f78ced54b@arm.com>
2021-05-17 5:47 ` Fwd: [Bug 213069] New: " Christophe Leroy
2021-05-17 5:55 ` Aneesh Kumar K.V
2021-05-17 7:25 ` Anshuman Khandual
2021-05-17 7:44 ` Aneesh Kumar K.V
2021-05-17 10:53 ` Anshuman Khandual
2021-05-17 11:14 ` Aneesh Kumar K.V
2021-05-17 12:49 ` Anshuman Khandual
2021-05-17 12:59 ` Christophe Leroy [this message]
2021-05-17 13:12 ` Anshuman Khandual
2021-05-17 15:26 ` Christophe Leroy
2021-05-17 13:52 ` Aneesh Kumar K.V
2021-05-17 14:12 ` Anshuman Khandual
2021-05-17 6:21 ` [Bug 213069] " bugzilla-daemon
2021-05-17 10:36 ` bugzilla-daemon
2021-05-17 12:57 ` bugzilla-daemon
2021-05-19 1:56 ` bugzilla-daemon
2021-06-04 0:36 ` bugzilla-daemon
2021-06-18 23:18 ` bugzilla-daemon
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