lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 22 Jul 2014 16:51:04 -0700
From:	Laura Abbott <>
To:	Catalin Marinas <>,
	Arnd Bergmann <>
CC:	"" 
	Will Deacon <>,
	David Riley <>,
	"" <>,
	"" <>,
	Ritesh Harjain <>
Subject: Re: [PATCHv4 5/5] arm64: Add atomic pool for non-coherent and CMA

On 7/22/2014 2:03 PM, Catalin Marinas wrote:
> On Tue, Jul 22, 2014 at 07:06:44PM +0100, Arnd Bergmann wrote:
>>> +               if (!addr)
>>> +                       goto destroy_genpool;
>>> +
>>> +               memset(addr, 0, atomic_pool_size);
>>> +               __dma_flush_range(addr, addr + atomic_pool_size);
>> It also seems weird to flush the cache on a virtual address of
>> an uncacheable mapping. Is that well-defined?
> Yes. According to D5.8.1 (Data and unified caches), "if cache
> maintenance is performed on a memory location, the effect of that cache
> maintenance is visible to all aliases of that physical memory location.
> These properties are consistent with implementing all caches that can
> handle data accesses as Physically-indexed, physically-tagged (PIPT)
> caches".

This was actually unintentional on my part. I'm going to clean this up
to flush via the existing cached mapping to make it clearer what's going

>> In the CMA case, the
>> original mapping should already be uncached here, so you don't need
>> to flush it.
> I don't think it is non-cacheable already, at least not for arm64 (CMA
> can be used on coherent architectures as well).

Memory allocated via dma_alloc_from_contiguous is not guaranteed to be
uncached. On arm, we allocate the page of memory and the remap it as

>> In the alloc_pages() case, I think you need to unmap
>> the pages from the linear mapping instead.
> Even if unmapped, it would not remove dirty cache lines (which are
> associated with physical addresses anyway). But we don't need to worry
> about unmapping anyway, see above (that's unless we find some
> architecture implementation where having such cacheable/non-cacheable
> aliases is not efficient enough, the efficiency is not guaranteed by the
> ARM ARM, just the correct behaviour).

Let's hope that never happens.


Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists