linux-kernel - Re: [PATCH v13 1/3] ioremap: Update pgtable free interfaces with addr

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Date:   Wed, 6 Jun 2018 16:44:38 +0100
From:   Will Deacon <will.deacon@....com>
To:     Chintan Pandya <cpandya@...eaurora.org>
Cc:     catalin.marinas@....com, mark.rutland@....com,
        akpm@...ux-foundation.org, toshi.kani@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH v13 1/3] ioremap: Update pgtable free interfaces with addr

On Wed, Jun 06, 2018 at 12:31:19PM +0530, Chintan Pandya wrote:
> From: Chintan Pandya <cpandya@...eaurora.org>
> 
> The following kernel panic was observed on ARM64 platform due to a stale
> TLB entry.
> 
>  1. ioremap with 4K size, a valid pte page table is set.
>  2. iounmap it, its pte entry is set to 0.
>  3. ioremap the same address with 2M size, update its pmd entry with
>     a new value.
>  4. CPU may hit an exception because the old pmd entry is still in TLB,
>     which leads to a kernel panic.
> 
> Commit b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page
> table") has addressed this panic by falling to pte mappings in the above
> case on ARM64.
> 
> To support pmd mappings in all cases, TLB purge needs to be performed
> in this case on ARM64.
> 
> Add a new arg, 'addr', to pud_free_pmd_page() and pmd_free_pte_page()
> so that TLB purge can be added later in seprate patches.
> 
> [toshi@....com: merge changes, rewrite patch description]
> Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
> Signed-off-by: Chintan Pandya <cpandya@...eaurora.org>
> Signed-off-by: Toshi Kani <toshi.kani@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: <stable@...r.kernel.org>
> 
> ---
>  arch/arm64/mm/mmu.c           | 4 ++--
>  arch/x86/mm/pgtable.c         | 8 +++++---
>  include/asm-generic/pgtable.h | 8 ++++----
>  lib/ioremap.c                 | 4 ++--
>  4 files changed, 13 insertions(+), 11 deletions(-)

Reviewed-by: Will Deacon <will.deacon@....com>

Thanks,

Will