From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoffer Dall <christoffer.dall@linaro.org>
Subject: Re: [PATCH 4/4] arm/arm64: KVM: use kernel mapping to perform
 invalidation on page fault
Date: Fri, 9 Jan 2015 13:51:13 +0100
Message-ID: <20150109125113.GT21092@cbox>
References: <1420718349-24152-1-git-send-email-marc.zyngier@arm.com>
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	Steve Capper <steve.capper@linaro.org>
To: Marc Zyngier <marc.zyngier@arm.com>
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On Thu, Jan 08, 2015 at 11:59:09AM +0000, Marc Zyngier wrote:
> When handling a fault in stage-2, we need to resync I$ and D$, just
> to be sure we don't leave any old cache line behind.
> 
> That's very good, except that we do so using the *user* address.
> Under heavy load (swapping like crazy), we may end up in a situation
> where the page gets mapped in stage-2 while being unmapped from
> userspace by another CPU.
> 
> At that point, the DC/IC instructions can generate a fault, which
> we handle with kvm->mmu_lock held. The box quickly deadlocks, user
> is unhappy.
> 
> Instead, perform this invalidation through the kernel mapping,
> which is guaranteed to be present. The box is much happier, and so
> am I.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

This looks good to me!

Thanks,
-Christoffer