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

[Vineet Gupta]

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@xxxxxxxxxx

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