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

From: Xiao Guangrong
Date: Thu Sep 05 2013 - 09:24:11 EST


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@xxxxxxxxxxxxxxxxxx>

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