linux-kernel - Re: [PATCH] [ARM] force dcache flush if dcache

lists.openwall.net		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 linux-hardening linux-cve-announce 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]

Message-ID: <4AD36376.60007@vflare.org>
Date:	Mon, 12 Oct 2009 22:42:22 +0530
From:	Nitin Gupta <ngupta@...are.org>
To:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	David Miller <davem@...emloft.net>,
	Nick Piggin <npiggin@...e.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH] [ARM] force dcache flush if dcache_dirty bit set

On 10/12/2009 10:33 PM, Russell King wrote:
> On Mon, Oct 12, 2009 at 05:09:53PM +0100, Hugh Dickins wrote:
>> Sorry to muddy the waters on this, if you and Dave are sure that
>> you have the right fix, down in your architectures, and that fix
>> isn't going to hurt your performance significantly.
> 
> If I look at the issue from this point of view:
> 
> - we are using PG_arch_1 to delay cache handling for the page
> 
> - if PG_arch_1 is set on a page, we set it explicitly because we
>   didn't do some flushing between the allocation of the page and
>   mapping it into userspace
> 
> - if a page with PG_arch_1 set ever gets to userspace, this can
>   only be because we did the lazy flushing thing
>

 
> I don't see that there should have been any bearing on whether a page
> has a mapping or not when we get to update_mmu_cache.  The issue here
> is that > if PG_arch_1 is set on a page, then we didn't flush it at
> the time when we believed it was appropriate to do so. <
> 


Presented so clearly by Russell and this is exactly what I meant, though
the example just focused on some particular swap case which I happen to
stumble upon while working on something similar.

Thanks,
Nitin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/