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[Xen-devel] Re: Xen MMU's requirement to pin pages RO and initial_memory

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: [Xen-devel] Re: Xen MMU's requirement to pin pages RO and initial_memory_mapping.
From: "H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx>
Date: Mon, 16 May 2011 14:54:39 -0700
Cc: "jeremy@xxxxxxxx" <jeremy@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, "hpa@xxxxxxxxx" <hpa@xxxxxxxxx>, "yinghai@xxxxxxxxxx" <yinghai@xxxxxxxxxx>
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On 05/16/2011 08:41 AM, Konrad Rzeszutek Wilk wrote:
>> They become pagetable pages when:
>> - they are explicitly pinned by pin_pagetable_pfn
>> - they are hooked into the current pagetable
> Ok, so could we use those two calls to trigger the pagetable walk
> and mark them RO as appropiate? Which call sites are those? The
> xen_set_pgd/xen_set_pud/xen_set_pmd ? Presumarily we don't have
> to do that for the PTE's that are already mapped (as
> xen_setup_kernel_pagetable, and xen_map_identity_early do this
> already).
>> Like you wrote, considering that the x86_64 version of
>> kernel_physical_mapping_init hooks the pagetable pages into the
>> currently used pagetable, it wouldn't be possible to mark the pagetable
>> pages RO after init_memory_mapping.

Doesn't Xen have some kind of compatibility mode which could be used
during setup?


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