| Message ID | 20200608062739.378902-1-aneesh.kumar@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/debug_vm_pgtable: Fix kernel crash with page table validate | expand |
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
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
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.
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))));
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(+)