* [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate
@ 2020-06-08 6:27 Aneesh Kumar K.V
2020-06-08 11:01 ` Anshuman Khandual
0 siblings, 1 reply; 4+ messages in thread
From: Aneesh Kumar K.V @ 2020-06-08 6:27 UTC (permalink / raw)
To: linux-mm; +Cc: akpm, linuxppc-dev, mpe, Aneesh Kumar K.V, anshuman.khandual
Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but
no THP support enabled based on platforms. For ex: with 4K
PAGE_SIZE ppc64 supports THP only with radix translation.
This results in below crash when running with hash translation and
4K PAGE_SIZE.
kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140!
cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860]
pc: c0000000018810f8: debug_vm_pgtable+0x480/0x8b0
lr: c0000000018810ec: debug_vm_pgtable+0x474/0x8b0
...
[c000000ff948faf0] c000000001880fec debug_vm_pgtable+0x374/0x8b0 (unreliable)
[c000000ff948fbf0] c000000000011648 do_one_initcall+0x98/0x4f0
[c000000ff948fcd0] c000000001843928 kernel_init_freeable+0x330/0x3fc
[c000000ff948fdb0] c0000000000122ac kernel_init+0x24/0x148
[c000000ff948fe20] c00000000000cc44 ret_from_kernel_thread+0x5c/0x78
Check for THP support correctly
Cc: anshuman.khandual@arm.com
Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
mm/debug_vm_pgtable.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 188c18908964..e60151c5e997 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -61,6 +61,9 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
{
pmd_t pmd = pfn_pmd(pfn, prot);
+ if (!has_transparent_hugepage())
+ return;
+
WARN_ON(!pmd_same(pmd, pmd));
WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate
2020-06-08 6:27 [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate Aneesh Kumar K.V
@ 2020-06-08 11:01 ` Anshuman Khandual
2020-06-08 11:16 ` Aneesh Kumar K.V
0 siblings, 1 reply; 4+ messages in thread
From: Anshuman Khandual @ 2020-06-08 11:01 UTC (permalink / raw)
To: Aneesh Kumar K.V, linux-mm; +Cc: akpm, linuxppc-dev, mpe
Hi Aneesh,
On 06/08/2020 11:57 AM, Aneesh Kumar K.V wrote:
> Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but
> no THP support enabled based on platforms. For ex: with 4K
> PAGE_SIZE ppc64 supports THP only with radix translation.
Good catch, never hit this before.
>
> This results in below crash when running with hash translation and
> 4K PAGE_SIZE.
>
> kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140!
> cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860]
> pc: c0000000018810f8: debug_vm_pgtable+0x480/0x8b0
> lr: c0000000018810ec: debug_vm_pgtable+0x474/0x8b0
> ...
> [c000000ff948faf0] c000000001880fec debug_vm_pgtable+0x374/0x8b0 (unreliable)
> [c000000ff948fbf0] c000000000011648 do_one_initcall+0x98/0x4f0
> [c000000ff948fcd0] c000000001843928 kernel_init_freeable+0x330/0x3fc
> [c000000ff948fdb0] c0000000000122ac kernel_init+0x24/0x148
> [c000000ff948fe20] c00000000000cc44 ret_from_kernel_thread+0x5c/0x78
>
> Check for THP support correctly
Makes sense, is this the only configuration which hit the problem ?
>
> Cc: anshuman.khandual@arm.com
> Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers")
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
> mm/debug_vm_pgtable.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 188c18908964..e60151c5e997 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -61,6 +61,9 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
> {
> pmd_t pmd = pfn_pmd(pfn, prot);
>
> + if (!has_transparent_hugepage())
> + return;
> +
We should also add this check to pud_basic_tests() as well.
> WARN_ON(!pmd_same(pmd, pmd));
> WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
> WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
>
The subject line here should mention about correct THP support
detection which fixes the problem. Probably something like this
or similar ("Fix kernel crash with correct THP support check").
- Anshuman
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate
2020-06-08 11:01 ` Anshuman Khandual
@ 2020-06-08 11:16 ` Aneesh Kumar K.V
2020-06-08 12:15 ` Anshuman Khandual
0 siblings, 1 reply; 4+ messages in thread
From: Aneesh Kumar K.V @ 2020-06-08 11:16 UTC (permalink / raw)
To: Anshuman Khandual, linux-mm; +Cc: akpm, linuxppc-dev, mpe
On 6/8/20 4:31 PM, Anshuman Khandual wrote:
> Hi Aneesh,
>
> On 06/08/2020 11:57 AM, Aneesh Kumar K.V wrote:
>> Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but
>> no THP support enabled based on platforms. For ex: with 4K
>> PAGE_SIZE ppc64 supports THP only with radix translation.
>
> Good catch, never hit this before.
>
>>
>> This results in below crash when running with hash translation and
>> 4K PAGE_SIZE.
>>
>> kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140!
>> cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860]
>> pc: c0000000018810f8: debug_vm_pgtable+0x480/0x8b0
>> lr: c0000000018810ec: debug_vm_pgtable+0x474/0x8b0
>> ...
>> [c000000ff948faf0] c000000001880fec debug_vm_pgtable+0x374/0x8b0 (unreliable)
>> [c000000ff948fbf0] c000000000011648 do_one_initcall+0x98/0x4f0
>> [c000000ff948fcd0] c000000001843928 kernel_init_freeable+0x330/0x3fc
>> [c000000ff948fdb0] c0000000000122ac kernel_init+0x24/0x148
>> [c000000ff948fe20] c00000000000cc44 ret_from_kernel_thread+0x5c/0x78
>>
>> Check for THP support correctly
>
> Makes sense, is this the only configuration which hit the problem ?
4K hash ppc64 is the only config i guess.
>
>>
>> Cc: anshuman.khandual@arm.com
>> Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers")
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>> ---
>> mm/debug_vm_pgtable.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 188c18908964..e60151c5e997 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -61,6 +61,9 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
>> {
>> pmd_t pmd = pfn_pmd(pfn, prot);
>>
>> + if (!has_transparent_hugepage())
>> + return;
>> +
>
> We should also add this check to pud_basic_tests() as well.
Do we have a function that check for runtime support for pud level THP?
ppc64 don't do pud level THP yet. So we have
CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD=n
are you suggesting we do the same check for pud level THP too?
>
>> WARN_ON(!pmd_same(pmd, pmd));
>> WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
>> WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
>>
>
> The subject line here should mention about correct THP support
> detection which fixes the problem. Probably something like this
> or similar ("Fix kernel crash with correct THP support check").
Not sure about that. This fix a kernel crash with page table validate code.
-aneesh
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate
2020-06-08 11:16 ` Aneesh Kumar K.V
@ 2020-06-08 12:15 ` Anshuman Khandual
0 siblings, 0 replies; 4+ messages in thread
From: Anshuman Khandual @ 2020-06-08 12:15 UTC (permalink / raw)
To: Aneesh Kumar K.V, linux-mm; +Cc: akpm, linuxppc-dev, mpe
On 06/08/2020 04:46 PM, Aneesh Kumar K.V wrote:
> On 6/8/20 4:31 PM, Anshuman Khandual wrote:
>> Hi Aneesh,
>>
>> On 06/08/2020 11:57 AM, Aneesh Kumar K.V wrote:
>>> Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but
>>> no THP support enabled based on platforms. For ex: with 4K
>>> PAGE_SIZE ppc64 supports THP only with radix translation.
>>
>> Good catch, never hit this before.
>>
>>>
>>> This results in below crash when running with hash translation and
>>> 4K PAGE_SIZE.
>>>
>>> kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140!
>>> cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860]
>>> pc: c0000000018810f8: debug_vm_pgtable+0x480/0x8b0
>>> lr: c0000000018810ec: debug_vm_pgtable+0x474/0x8b0
>>> ...
>>> [c000000ff948faf0] c000000001880fec debug_vm_pgtable+0x374/0x8b0 (unreliable)
>>> [c000000ff948fbf0] c000000000011648 do_one_initcall+0x98/0x4f0
>>> [c000000ff948fcd0] c000000001843928 kernel_init_freeable+0x330/0x3fc
>>> [c000000ff948fdb0] c0000000000122ac kernel_init+0x24/0x148
>>> [c000000ff948fe20] c00000000000cc44 ret_from_kernel_thread+0x5c/0x78
>>>
>>> Check for THP support correctly
>>
>> Makes sense, is this the only configuration which hit the problem ?
>
> 4K hash ppc64 is the only config i guess.
Okay.
>
>>
>>>
>>> Cc: anshuman.khandual@arm.com
>>> Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers")
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>>> ---
>>> mm/debug_vm_pgtable.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>>> index 188c18908964..e60151c5e997 100644
>>> --- a/mm/debug_vm_pgtable.c
>>> +++ b/mm/debug_vm_pgtable.c
>>> @@ -61,6 +61,9 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
>>> {
>>> pmd_t pmd = pfn_pmd(pfn, prot);
>>> + if (!has_transparent_hugepage())
>>> + return;
>>> +
>>
>> We should also add this check to pud_basic_tests() as well.
>
>
> Do we have a function that check for runtime support for pud level THP? ppc64 don't do pud level THP yet. So we have
> CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD=n
I believe, we dont have such a generic function. Please correct me, if I am
missing something here.
>
> are you suggesting we do the same check for pud level THP too?
Yes. Because regardless CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD, could there
be any THP at PUD level when has_transparent_hugepage() returns negative ? The
current dependency between THP and PUD THP configs seems some what confusing
but having this check at PUD level should protect against similar problems. A
quick test (after adding this check to PUD level) on x86 does not indicate any
problem on the normal path.
>
>
>>
>>> WARN_ON(!pmd_same(pmd, pmd));
>>> WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
>>> WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
>>>
>>
>> The subject line here should mention about correct THP support
>> detection which fixes the problem. Probably something like this
>> or similar ("Fix kernel crash with correct THP support check").
>
>
> Not sure about that. This fix a kernel crash with page table validate code.
What this fixes is very clear from the prefix itself - "mm/debug_vm_pgtable:",
making "page table validate" some what bit redundant. Instead, it could just
accommodate method of the fix i.e "via correct THP support check". Nonetheless,
it is just a small nit.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-06-08 12:15 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-08 6:27 [PATCH] mm/debug_vm_pgtable: Fix kernel crash with page table validate Aneesh Kumar K.V
2020-06-08 11:01 ` Anshuman Khandual
2020-06-08 11:16 ` Aneesh Kumar K.V
2020-06-08 12:15 ` Anshuman Khandual
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).