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From: mark.rutland@arm.com (Mark Rutland)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3] arm64: mm: move zero page from .bss to right before swapper_pg_dir
Date: Tue, 13 Sep 2016 18:35:08 +0100	[thread overview]
Message-ID: <20160913173507.GA29678@leverpostej> (raw)
In-Reply-To: <1473696925-26156-1-git-send-email-ard.biesheuvel@linaro.org>

Hi,

On Mon, Sep 12, 2016 at 05:15:25PM +0100, Ard Biesheuvel wrote:
> Move the statically allocated zero page from the .bss section to right
> before swapper_pg_dir. This allows us to refer to its physical address
> by simply reading TTBR1_EL1 (which always points to swapper_pg_dir and
> always has its ASID field cleared), and subtracting PAGE_SIZE.

It might be worth worth mentioning that we want to do this to make
cpu_set_reserved_ttbr0() as cheap as possible for the TTBR0_SW_PAN
stuff, as that'll mean we're calling it far more frequently.

> To protect the zero page from inadvertent modification, carve out a
> segment that covers it as well as idmap_pg_dir[], and mark it read-only
> in both the primary and the linear mappings of the kernel.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Otherwise, this looks good to me, builds without warnings, and works on
Juno and Seattle without issue even when I throw the usual set of
problematic config options at it. Which is to say:

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

  reply	other threads:[~2016-09-13 17:35 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-12 16:15 [PATCH v3] arm64: mm: move zero page from .bss to right before swapper_pg_dir Ard Biesheuvel
2016-09-13 17:35 ` Mark Rutland [this message]
2016-09-13 19:18   ` Ard Biesheuvel
2016-09-13 20:24     ` Mark Rutland
2016-09-13 20:29       ` Ard Biesheuvel
2016-09-14 10:19         ` Mark Rutland
2016-10-07  9:31 ` Ard Biesheuvel
2016-10-09 23:10   ` Mark Rutland
2016-10-10  9:14     ` Ard Biesheuvel

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