linux-kernel - Re: [PATCH v2] KVM: mmu: allow page tables to be in read-only slots

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Message-ID: <522885DB.2090204@linux.vnet.ibm.com>
Date:	Thu, 05 Sep 2013 21:23:39 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kvm@...r.kernel.org, Gleb Natapov <gleb@...hat.com>
Subject: Re: [PATCH v2] KVM: mmu: allow page tables to be in read-only slots

On 09/05/2013 08:21 PM, Paolo Bonzini wrote:
> Page tables in a read-only memory slot will currently cause a triple
> fault when running with shadow paging, because the page walker uses
> gfn_to_hva and it fails on such a slot.
> 
> TianoCore uses such a page table.  The idea is that, on real hardware,
> the firmware can already run in 64-bit flat mode when setting up the
> memory controller.  Real hardware seems to be fine with that as long as
> the accessed/dirty bits are set.  Thus, this patch saves whether the
> slot is readonly, and later checks it when updating the accessed and
> dirty bits.
> 
> Note that this scenario is not supported by NPT at all, as explained by
> comments in the code.

Reviewed-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>

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