From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Wed, 6 Feb 2013 12:33:07 +0000 Subject: [PATCH v4] ARM: LPAE: Fix mapping in alloc_init_pte for unaligned addresses In-Reply-To: <20130206122213.GF17833@n2100.arm.linux.org.uk> References: <1359472036-7613-1-git-send-email-r.sricharan@ti.com> <20130201162631.GG5151@arm.com> <20130201163722.GH5151@arm.com> <20130201174246.GJ5151@arm.com> <510F3BA8.8070700@ti.com> <510F3CA3.7080604@ti.com> <20130206121523.GD26454@arm.com> <20130206122213.GF17833@n2100.arm.linux.org.uk> Message-ID: <20130206123307.GE26454@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Feb 06, 2013 at 12:22:13PM +0000, Russell King - ARM Linux wrote: > On Wed, Feb 06, 2013 at 12:15:23PM +0000, Catalin Marinas wrote: > > The problem with the classic MMU is that if we have a 1MB range we can > > end up with just page mappings. The code is currently buggy since if we > > have create_mapping() for a 1MB range and later create_mapping() for a > > 4KB in the next MB, the first 1MB is removed. > > And that is where we rely on people calling create_mapping() - who > will be the SoC porters - not to be idiotic and do that kind of thing. > That's worked fine for the last 10+ years so there's no need to make > the code any more complex by trying to fix something that really isn't > a problem. > > I wouldn't be surprised if we have some mappings which are created by > 4K page tables, and then one half of the page table is overwritten by > a section mapping - so trying to fix this _may_ be risky. If the 4K is called first, it should be fine. But some WARN_ON() calls wouldn't hurt, just to be sure. It's not a fast path anyway. -- Catalin