Re: [Xen-devel] [PATCH v2] VMX: don't allow PVH to reach handle_mmio()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.12.14 at 18:49, <roger.pau@xxxxxxxxxx> wrote:
> El 09/12/14 a les 18.19, Jan Beulich ha escrit:
>>>>> On 09.12.14 at 18:01, <roger.pau@xxxxxxxxxx> wrote:
>>> For 4.6 I think we need to start using a different hvm_io_bitmap for PVH
>>> Dom0 that allows direct access to the IO ports, bypassing the vmexit and
>>> simplifying the code in Xen (this would also fix INS/OUTS). Still not
>>> sure what should be done for PVH DomUs, specially when PVH gains support
>>> for pci-passthrough.
>> 
>> With the difficulty being that for PV the hypervisor intentionally
>> intercepts accesses to some of the ports, so we can't blindly
>> allow PVH access to all the ports its allowed access to.
> 
> I assume this is mainly for DomUs but not for Dom0? Or should PVH Dom0
> access to the IO space also be filtered and emulated for some ports?

It should indeed - just look at guest_io_read() and guest_io_write().
I.e. an eventual PVH specific bitmap would need to be populated
based on what admin_io_okay() returns (instead of
ioports_access_permitted()), carefully taking into consideration the
possible access widths.

Jan


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