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* Re: [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements
       [not found]   ` <d96fa0d8-98d8-c924-99f7-bb9673fc2a13@redhat.com>
@ 2021-08-13 19:43     ` Vineet Gupta
  2021-08-14  2:57       ` Gavin Shan
  0 siblings, 1 reply; 2+ messages in thread
From: Vineet Gupta @ 2021-08-13 19:43 UTC (permalink / raw)
  To: Gavin Shan, Anshuman Khandual, linux-mm
  Cc: linux-kernel, gerald.schaefer, aneesh.kumar, christophe.leroy,
	cai, catalin.marinas, will, akpm, chuhu, shan.gavin, arcml

On 8/13/21 2:25 AM, Gavin Shan wrote:
> Hi Anshuman and Vineet,
>
> On 8/12/21 9:11 PM, Anshuman Khandual wrote:
>> On 8/9/21 2:56 PM, Gavin Shan wrote:
>>> There are couple of issues with current implementations and this series
>>> tries to resolve the issues:
>>>
>>>    (a) All needed information are scattered in variables, passed to 
>>> various
>>>        test functions. The code is organized in pretty much relaxed 
>>> fashion.
>>>
>>>    (b) The page isn't allocated from buddy during page table entry 
>>> modifying
>>>        tests. The page can be invalid, conflicting to the 
>>> implementations
>>>        of set_xxx_at() on ARM64. The target page is accessed so that 
>>> the
>>>        iCache can be flushed when execution permission is given on 
>>> ARM64.
>>>        Besides, the target page can be unmapped and accessing to it 
>>> causes
>>>        kernel crash.
>>>
>>> "struct pgtable_debug_args" is introduced to address issue (a). For 
>>> issue
>>> (b), the used page is allocated from buddy in page table entry 
>>> modifying
>>> tests. The corresponding tets will be skipped if we fail to allocate 
>>> the
>>> (huge) page. For other test cases, the original page around to kernel
>>> symbol (@start_kernel) is still used.
>>>
>>> The patches are organized as below. PATCH[2-10] could be combined to 
>>> one
>>> patch, but it will make the review harder:
>>>
>>>    PATCH[1] introduces "struct pgtable_debug_args" as place holder 
>>> of all
>>>             needed information. With it, the old and new implementation
>>>             can coexist.
>>>    PATCH[2-10] uses "struct pgtable_debug_args" in various test 
>>> functions.
>>>    PATCH[11] removes the unused code for old implementation.
>>>    PATCH[12] fixes the issue of corrupted page flag for ARM64
>>>
>>> Changelog
>>> =========
>>> v6:
>>>     * Populate saved page table entry pointers after
>>>       they're allocated in init_args() (Anshuman)
>>>     * Fix imbalanced preemption count issue by replacing
>>>       pte_alloc_mmap() with pte_alloc() in init_args() (syzbot)
>>
>> + vgupta@kernel.org

Please also keep linux-snps-arc CC'ed for ARC changes.

>>
>> Hello Gavin/Vineet,
>>
>> This series still need to be tested on ARC ?
>>
>
> Yes, I'm unable to test ARC as it's not supported by QEMU yet.
> It would great if Vineet can give it a try on ARC :)

We do have a working QEMU (in the process of being upstreamed) you could try
https://github.com/foss-for-synopsys-dwc-arc-processors/qemu #master

Is this code in some shared git repo we can pull - instead of apply 8 files.

Thx,
-Vineet

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^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements
  2021-08-13 19:43     ` [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements Vineet Gupta
@ 2021-08-14  2:57       ` Gavin Shan
  0 siblings, 0 replies; 2+ messages in thread
From: Gavin Shan @ 2021-08-14  2:57 UTC (permalink / raw)
  To: Vineet Gupta, Anshuman Khandual, linux-mm
  Cc: linux-kernel, gerald.schaefer, aneesh.kumar, christophe.leroy,
	cai, catalin.marinas, will, akpm, chuhu, shan.gavin, arcml

Hi Vineet,

On 8/14/21 5:43 AM, Vineet Gupta wrote:
> On 8/13/21 2:25 AM, Gavin Shan wrote:
>> On 8/12/21 9:11 PM, Anshuman Khandual wrote:
>>> On 8/9/21 2:56 PM, Gavin Shan wrote:
>>>> There are couple of issues with current implementations and this series
>>>> tries to resolve the issues:
>>>>
>>>>    (a) All needed information are scattered in variables, passed to various
>>>>        test functions. The code is organized in pretty much relaxed fashion.
>>>>
>>>>    (b) The page isn't allocated from buddy during page table entry modifying
>>>>        tests. The page can be invalid, conflicting to the implementations
>>>>        of set_xxx_at() on ARM64. The target page is accessed so that the
>>>>        iCache can be flushed when execution permission is given on ARM64.
>>>>        Besides, the target page can be unmapped and accessing to it causes
>>>>        kernel crash.
>>>>
>>>> "struct pgtable_debug_args" is introduced to address issue (a). For issue
>>>> (b), the used page is allocated from buddy in page table entry modifying
>>>> tests. The corresponding tets will be skipped if we fail to allocate the
>>>> (huge) page. For other test cases, the original page around to kernel
>>>> symbol (@start_kernel) is still used.
>>>>
>>>> The patches are organized as below. PATCH[2-10] could be combined to one
>>>> patch, but it will make the review harder:
>>>>
>>>>    PATCH[1] introduces "struct pgtable_debug_args" as place holder of all
>>>>             needed information. With it, the old and new implementation
>>>>             can coexist.
>>>>    PATCH[2-10] uses "struct pgtable_debug_args" in various test functions.
>>>>    PATCH[11] removes the unused code for old implementation.
>>>>    PATCH[12] fixes the issue of corrupted page flag for ARM64
>>>>
>>>> Changelog
>>>> =========
>>>> v6:
>>>>     * Populate saved page table entry pointers after
>>>>       they're allocated in init_args() (Anshuman)
>>>>     * Fix imbalanced preemption count issue by replacing
>>>>       pte_alloc_mmap() with pte_alloc() in init_args() (syzbot)
>>>
>>> + vgupta@kernel.org
> 
> Please also keep linux-snps-arc CC'ed for ARC changes.
> 

Sure.

>>>
>>> Hello Gavin/Vineet,
>>>
>>> This series still need to be tested on ARC ?
>>>
>>
>> Yes, I'm unable to test ARC as it's not supported by QEMU yet.
>> It would great if Vineet can give it a try on ARC :)
> 
> We do have a working QEMU (in the process of being upstreamed) you could try
> https://github.com/foss-for-synopsys-dwc-arc-processors/qemu #master
> 
> Is this code in some shared git repo we can pull - instead of apply 8 files.
> 

Here is repo with v6 series included. Please help to have
a try.

    https://github.com/gwshan/linux  # kvm/arm64_debug

I tried to build the cross-compiler with buildroot with following
2 repos. Unfortunately, none of them worked for me. The QEMU
binary can be built successfully with the provided repo though.


[1] git://github.com/foss-for-synopsys-dwc-arc-processors/buildroot.git
     (branch: master)

     There are build errors after choosing little-endian ARM from
     "make menuconfig"

[2] https://github.com/buildroot/buildroot
     (branch: master)

     The build is successful, but the kernel can't be built because
     of the following errors:
    
     # make ARCH=arc CROSS_COMPILE=arc-linux- axs103_smp_defconfig
     # make -j 40
        :
     LD      vmlinux.o
     arc-linux-ld: error: attempting to link /home/gavin/sandbox/buildroot/buildroot.arc/output/host/lib
     /gcc/arc-buildroot-linux-uclibc/10.2.0/libgcc.a(_muldi3.o) with a binary vmlinux.o of different
     architecture

Thanks,
Gavin


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2021-08-13 19:43     ` [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements Vineet Gupta
2021-08-14  2:57       ` Gavin Shan

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