Re: [Xen-devel] [PATCH v1 for-4.6 2/2] xen: prevent access to HPET from Dom0

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/12/14 09:11, Jan Beulich wrote:
>>>> On 18.12.14 at 19:51, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 18/12/14 18:27, Roger Pau Monne wrote:
>>> Prevent Dom0 from accessing HPET MMIO region by adding it to the list of
>>> denied memory regions.
>>>
>>> Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
>>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Apologies that this reply is split between patch 0 and 2 - I replied to
>> your cover letter before reading this patch.
>>
>> Denying access is only valid if acpi_table_hpet.flags & 
>> ACPI_HPET_PAGE_PROTECT4 is true.
> Having just checked (as an example) the most modern Intel box I
> have direct access to, I wonder how many systems actually supply
> other than 0 here. Perhaps we ought to at once add a command
> line option to trigger the denial?

I also can't find a server which sets this flag.  I wonder how many
systems actually have other things sitting in the remainder of the page.

~Andrew


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