Re: [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements

From: Anshuman Khandual
Date: Thu Aug 12 2021 - 07:11:18 EST

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@xxxxxxxxxx

Hello Gavin/Vineet,

This series still need to be tested on ARC ?

- Anshuman