From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
kernel-team@android.com, linux-arm-kernel@lists.infradead.org,
Nicolas Pitre <nico@fluxnic.net>
Subject: Re: [PATCH v2 3/3] ARM: cache-v7: get rid of mini-stack
Date: Mon, 1 Mar 2021 15:53:39 +0000 [thread overview]
Message-ID: <20210301155339.GW1463@shell.armlinux.org.uk> (raw)
In-Reply-To: <20210210185532.8425-4-ardb@kernel.org>
On Wed, Feb 10, 2021 at 07:55:32PM +0100, Ard Biesheuvel wrote:
> Now that we have reduced the number of registers that we need to
> preserve when calling v7_invalidate_l1 from the boot code, we can use
> scratch registers to preserve the remaining ones, and get rid of the
> mini stack entirely. This works around any issues regarding cache
> behavior in relation to the uncached accesses to this memory, which is
> hard to get right in the general case (i.e., both bare metal and under
> virtualization)
>
> While at it, switch v7_invalidate_l1 to using ip as a scratch register
> instead of r4. This makes the function AAPCS compliant, and removes the
> need to stash r4 in ip across the call.
You don't mention that we only do this for MP capable cores, which
is in itself quite a big change - maybe that change should be a
separate commit?
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2021-03-01 15:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 18:55 [PATCH v2 0/3] ARM: v7: get rid of boot time mini stack Ard Biesheuvel
2021-02-10 18:55 ` [PATCH v2 1/3] ARM: cache-v7: add missing ISB after cache level selection Ard Biesheuvel
2021-02-10 18:55 ` [PATCH v2 2/3] ARM: cache-v7: refactor v7_invalidate_l1 to avoid clobbering r5/r6 Ard Biesheuvel
2021-02-10 18:55 ` [PATCH v2 3/3] ARM: cache-v7: get rid of mini-stack Ard Biesheuvel
2021-03-01 15:53 ` Russell King - ARM Linux admin [this message]
2021-03-01 16:10 ` Ard Biesheuvel
2021-03-01 14:38 ` [PATCH v2 0/3] ARM: v7: get rid of boot time mini stack Linus Walleij
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