linux-kernel - Re: [PATCH] kvm: Fix page ageing bugs

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Date:	Mon, 22 Sep 2014 16:18:42 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andres Lagar-Cavilla <andreslc@...gle.com>,
	Gleb Natapov <gleb@...nel.org>,
	Radim Krcmar <rkrcmar@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Peter Feiner <pfeiner@...gle.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
CC:	Andres Lagar-Cavilla <andreslc@...ogle.com>
Subject: Re: [PATCH] kvm: Fix page ageing bugs

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On 09/22/2014 03:57 PM, Andres Lagar-Cavilla wrote:
> 1. We were calling clear_flush_young_notify in unmap_one, but we
> are within an mmu notifier invalidate range scope. The spte exists
> no more (due to range_start) and the accessed bit info has already
> been propagated (due to kvm_pfn_set_accessed). Simply call 
> clear_flush_young.
> 
> 2. We clear_flush_young on a primary MMU PMD, but this may be
> mapped as a collection of PTEs by the secondary MMU (e.g. during
> log-dirty). This required expanding the interface of the
> clear_flush_young mmu notifier, so a lot of code has been trivially
> touched.
> 
> 3. In the absence of shadow_accessed_mask (e.g. EPT A bit), we
> emulate the access bit by blowing the spte. This requires proper
> synchronizing with MMU notifier consumers, like every other removal
> of spte's does.

Acked-by: Rik van Riel <riel@...hat.com>


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