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Re: [Xen-devel] [PATCH v6 11/14] arm/mem_access: Add software guest-page-table walk

Hi Sergej,

On 06/07/17 12:50, Sergej Proskurin wrote:
The function p2m_mem_access_check_and_get_page in mem_access.c
translates a gva to an ipa by means of the hardware functionality of the
ARM architecture. This is implemented in the function gva_to_ipa. If
mem_access is active, hardware-based gva to ipa translation might fail,
as gva_to_ipa uses the guest's translation tables, access to which might
be restricted by the active VTTBR. To address this issue, in this commit
we add a software-based guest-page-table walk, which will be used by the
function p2m_mem_access_check_and_get_page perform the gva to ipa
translation in software in one of the following commits.

Note: The introduced function guest_walk_tables assumes that the domain,
the gva of which is to be translated, is running on the currently active
vCPU. To walk the guest's page tables on a different vCPU, the following
registers would need to be loaded: TCR_EL1, TTBR0_EL1, TTBR1_EL1, and

Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>

Acked-by: Julien Grall <julien.grall@xxxxxxx>


Julien Grall

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