From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V4 2/2] arm: mm: Switch back to L_PTE_WRITE
Date: Fri, 20 Jun 2014 10:21:35 +0100 [thread overview]
Message-ID: <20140620092135.GK25104@arm.com> (raw)
In-Reply-To: <1402929159-11028-3-git-send-email-steve.capper@linaro.org>
On Mon, Jun 16, 2014 at 03:32:39PM +0100, Steve Capper wrote:
> For LPAE, we have the following means for encoding writable or dirty
> ptes:
> L_PTE_DIRTY L_PTE_RDONLY
> !pte_dirty && !pte_write 0 1
> !pte_dirty && pte_write 0 1
> pte_dirty && !pte_write 1 1
> pte_dirty && pte_write 1 0
>
> So we can't distinguish between writable clean ptes and read only
> ptes. This can cause problems with ptes being incorrectly flagged as
> read only when they are writable but not dirty.
>
> This patch re-introduces the L_PTE_WRITE bit for both short descriptors
> and long descriptors, by reverting
> 36bb94b ARM: pgtable: provide RDONLY page table bit rather than WRITE bit
>
> For short descriptors the L_PTE_RDONLY bit is renamed to L_PTE_WRITE
> and the pertinent logic changed. For long descriptors, L_PTE_WRITE is
> implemented as a new software bit.
>
> HugeTLB pages will use the L_PTE_WRITE semantics automatically.
>
> We need to add some logic to Transparent HugePages to ensure that they
> correctly interpret the revised pgprot permissions.
I think this look alright, but it certainly needs some stress testing. Have
you given it a good hammering? If so, this could use some exposure in -next.
Reviewed-by: Will Deacon <will.deacon@arm•com>
Will
next prev parent reply other threads:[~2014-06-20 9:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-16 14:32 [PATCH V4 0/2] PTE fixes for ARM LPAE Steve Capper
2014-06-16 14:32 ` [PATCH V4 1/2] arm: mm: Introduce {pte, pmd}_isset and {pte, pmd}_isclear Steve Capper
2014-06-20 9:12 ` [PATCH V4 1/2] arm: mm: Introduce {pte,pmd}_isset and {pte,pmd}_isclear Will Deacon
2014-06-20 10:04 ` Russell King - ARM Linux
2014-06-16 14:32 ` [PATCH V4 2/2] arm: mm: Switch back to L_PTE_WRITE Steve Capper
2014-06-20 9:21 ` Will Deacon [this message]
2014-06-20 13:23 ` Steve Capper
2014-06-20 18:17 ` Russell King - ARM Linux
2014-06-23 11:17 ` Catalin Marinas
2014-06-23 15:07 ` Steve Capper
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