linux-kernel - Re: [mm/debug] f8bf55f05f: BUG:non-zero_pgtables_bytes_on_freeing

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Date:   Sun, 29 Mar 2020 20:07:38 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     kernel test robot <lkp@...el.com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Qian Cai <cai@....pw>,
        Catalin Marinas <catalin.marinas@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Will Deacon <will@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [mm/debug] f8bf55f05f: BUG:non-zero_pgtables_bytes_on_freeing_mm


On 03/28/2020 06:37 PM, kernel test robot wrote:
> [    9.304270] debug_vm_pgtable: debug_vm_pgtable: Validating architecture page table helpers
> [    9.306147] random: get_random_u32 called from debug_vm_pgtable+0x2c/0x6a5 with crng_init=1
> [    9.306206] BUG: non-zero pgtables_bytes on freeing mm: -4096

This problem is on i386 platform via CONFIG_EXPERT with CONFIG_X86_PAE
still enabled. This particular configuration is not supported (even if
it could be tested via CONFIG_EXPERT) with ARCH_HAS_DEBUG_VM_PGTABLE.

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index beea77046f9b..df8a19e52e82 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -61,6 +61,7 @@  config X86
 	select ARCH_CLOCKSOURCE_INIT
 	select ARCH_HAS_ACPI_TABLE_UPGRADE	if ACPI
 	select ARCH_HAS_DEBUG_VIRTUAL
+	select ARCH_HAS_DEBUG_VM_PGTABLE	if !X86_PAE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FAST_MULTIPLIER