From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f193.google.com ([209.85.160.193]:39161 "EHLO mail-qt1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726090AbgCFUoq (ORCPT ); Fri, 6 Mar 2020 15:44:46 -0500 Received: by mail-qt1-f193.google.com with SMTP id e13so2746404qts.6 for ; Fri, 06 Mar 2020 12:44:45 -0800 (PST) Message-ID: <1583527481.7365.165.camel@lca.pw> Subject: Re: [PATCH V15] mm/debug: Add tests validating architecture page table helpers From: Qian Cai Date: Fri, 06 Mar 2020 15:44:41 -0500 In-Reply-To: <1583452659-11801-1-git-send-email-anshuman.khandual@arm.com> References: <1583452659-11801-1-git-send-email-anshuman.khandual@arm.com> Content-Type: text/plain; charset="utf-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , Mike Rapoport , Vineet Gupta , Catalin Marinas , Will Deacon , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "Kirill A . Shutemov" , Paul Walmsley , Palmer Dabbelt , linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Christophe Leroy On Fri, 2020-03-06 at 05:27 +0530, 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 > inside kernel_init() right after async_synchronize_full(). > > This test gets built and run when CONFIG_DEBUG_VM_PGTABLE is selected. Any > architecture, which is willing to subscribe this test will need to select > ARCH_HAS_DEBUG_VM_PGTABLE. For now this is limited to arc, arm64, x86, s390 > and ppc32 platforms where the test is known to build and run successfully. > Going forward, other architectures too can subscribe the test after fixing > any build or runtime problems with their page table helpers. Meanwhile for > better platform coverage, the test can also be enabled with CONFIG_EXPERT > even without ARCH_HAS_DEBUG_VM_PGTABLE. > > 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. OK, I get this working on powerpc hash MMU as well, so this? diff --git a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt index 64d0f9b15c49..c527d05c0459 100644 --- a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt +++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt @@ -22,8 +22,7 @@      |       nios2: | TODO |      |    openrisc: | TODO |      |      parisc: | TODO | -    |  powerpc/32: |  ok  | -    |  powerpc/64: | TODO | +    |     powerpc: |  ok  |      |       riscv: | TODO |      |        s390: |  ok  |      |          sh: | TODO | diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 2e7eee523ba1..176930f40e07 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -116,7 +116,7 @@ config PPC   #   select ARCH_32BIT_OFF_T if PPC32   select ARCH_HAS_DEBUG_VIRTUAL - select ARCH_HAS_DEBUG_VM_PGTABLE if PPC32 + select ARCH_HAS_DEBUG_VM_PGTABLE   select ARCH_HAS_DEVMEM_IS_ALLOWED   select ARCH_HAS_ELF_RANDOMIZE   select ARCH_HAS_FORTIFY_SOURCE diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index 96a91bda3a85..98990a515268 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -256,7 +256,8 @@ static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,   pte_t pte = READ_ONCE(*ptep);     pte = __pte(pte_val(pte) | RANDOM_ORVALUE); - WRITE_ONCE(*ptep, pte); + set_pte_at(mm, vaddr, ptep, pte); + barrier();   pte_clear(mm, vaddr, ptep);   pte = READ_ONCE(*ptep);   WARN_ON(!pte_none(pte));