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

Will Deacon
2018-06-06T15:44:08Z

On Wed, Jun 06, 2018 at 12:31:19PM +0530, Chintan Pandya wrote:
> From: Chintan Pandya <cpandya@codeaurora.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@hpe.com: merge changes, rewrite patch description]
> Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
> Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
> Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: <stable@vger.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@arm.com>

Thanks,

Will