linux-kernel - Re: [PATCH V8] mm/debug: Add tests validating architecture page table helpers

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Message-ID: <e0aa8d49-5511-15e4-f413-62c99eea4fab@arm.com>
Date:   Tue, 5 Nov 2019 05:30:41 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Steven Price <Steven.Price@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kees Cook <keescook@...omium.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Matthew Wilcox <willy@...radead.org>,
        Sri Krishna chowdary <schowdary@...dia.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Vineet Gupta <vgupta@...opsys.com>,
        James Hogan <jhogan@...nel.org>,
        Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Ingo Molnar <mingo@...nel.org>,
        linux-snps-arc@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH V8] mm/debug: Add tests validating architecture page table
 helpers



On 10/28/2019 10:59 AM, Anshuman Khandual wrote:
> This adds tests which will validate architecture page table helpers and
> other accessors in their compliance with expected generic MM semantics.
> This will help various architectures in validating changes to existing
> page table helpers or addition of new ones.
> 
> This test covers basic page table entry transformations including but not
> limited to old, young, dirty, clean, write, write protect etc at various
> level along with populating intermediate entries with next page table page
> and validating them.
> 
> Test page table pages are allocated from system memory with required size
> and alignments. The mapped pfns at page table levels are derived from a
> real pfn representing a valid kernel text symbol. This test gets called
> right after page_alloc_init_late().
> 
> This gets build and run when CONFIG_DEBUG_VM_PGTABLE is selected along with
> CONFIG_VM_DEBUG. Architectures willing to subscribe this test also need to
> select CONFIG_ARCH_HAS_DEBUG_VM_PGTABLE which for now is limited to x86 and
> arm64. Going forward, other architectures too can enable this after fixing
> build or runtime problems (if any) with their page table helpers.
> 
> Folks interested in making sure that a given platform's page table helpers
> conform to expected generic MM semantics should enable the above config
> which will just trigger this test during boot. Any non conformity here will
> be reported as an warning which would need to be fixed. This test will help
> catch any changes to the agreed upon semantics expected from generic MM and
> enable platforms to accommodate it thereafter.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Steven Price <Steven.Price@....com>
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Sri Krishna chowdary <schowdary@...dia.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Russell King - ARM Linux <linux@...linux.org.uk>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: James Hogan <jhogan@...nel.org>
> Cc: Paul Burton <paul.burton@...s.com>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: Kirill A. Shutemov <kirill@...temov.name>
> Cc: Gerald Schaefer <gerald.schaefer@...ibm.com>
> Cc: Christophe Leroy <christophe.leroy@....fr>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: linux-snps-arc@...ts.infradead.org
> Cc: linux-mips@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-ia64@...r.kernel.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-s390@...r.kernel.org
> Cc: linux-sh@...r.kernel.org
> Cc: sparclinux@...r.kernel.org
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> 
> Tested-by: Christophe Leroy <christophe.leroy@....fr>		#PPC32
> Suggested-by: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> 
> This adds a test validation for architecture exported page table helpers.
> Patch adds basic transformation tests at various levels of the page table.
> 
> This test was originally suggested by Catalin during arm64 THP migration
> RFC discussion earlier. Going forward it can include more specific tests
> with respect to various generic MM functions like THP, HugeTLB etc and
> platform specific tests.
> 
> https://lore.kernel.org/linux-mm/20190628102003.GA56463@arrakis.emea.arm.com/
> 
> Needs to be applied on linux-next (next-20191025).
> 
> Changes in V8:
> 
> - Enabled ARCH_HAS_DEBUG_VM_PGTABLE on PPC32 platform per Christophe
> - Updated feature documentation as DEBUG_VM_PGTABLE is now enabled on PPC32 platform
> - Moved ARCH_HAS_DEBUG_VM_PGTABLE earlier to indent it with DEBUG_VM per Christophe
> - Added an information message in debug_vm_pgtable() per Christophe
> - Dropped random_vaddr boundary condition checks per Christophe and Qian
> - Replaced virt_addr_valid() check with pfn_valid() check in debug_vm_pgtable()

Hello Andrew,

Just wondering if this version looks okay or is there anything else which still
needs to be accommodated here first, before this test can be considered for merging ?
Thank you.

- Anshuman