RE: [Xen-devel] [PATCH] [VT] add BT instruction support to VMXMMIO decoder

["Li, Xin B" <xin.b.li@xxxxxxxxx>]

>This seems a little questionable:
>
>- in handle_mmio()'s INSTR_BT case value should be signed, not unsigned
>(see definition of BitOffset in IA32 SDM Vol 2a Section 3.1)

Thanks.

>- in the same place, you implicitly assume that va and gpa are
>congruent over a range 2**29/2**61 bytes, which is likely wrong,
>especially for mmio regions (while one could argue that there shouldn't
>be accesses with a base address pointing into one mmio region, but the
>effective address with the shifted bit offset included pointing into a
>different on, I believe the hypervisor should actually verify this and
>either handle it properly or fail the request)
>- the alignment (and thus implicit range) limitations of real hardware
>aren't followed (for e.g. a 32-bit operation, hardware confines the
>access to the aligned 32-bit quantity addressed by 
>EA+4*(BitOffset/32));
>to match that you should either pass 1 instead of mmio_inst.op_size to
>send_mmio_req, or you should calculate the offset from gpa depending on
>the operand size (which is probably the better solution, although I
>don't know which of the two possible mechanisms real hardware uses)

Yes, this is not perfect.
Can you help?

>
>Jan
>
>>>> "Li, Xin B" <xin.b.li@xxxxxxxxx> 15.10.05 08:14:03 >>>
>add BT instruction support to VMX MMIO decoder.
>Also extends TEST and OR instructions support for 16/32 bit
>operations,
>these are needed for windows.
>
>Signed-off-by: Xin Li <xin.b.li@xxxxxxxxx>
>Signed-off-by: Chengyuan Li <chengyuan.li@xxxxxxxxx>
>Signed-off-by: Nakajima Jun <nakajima.jun@xxxxxxxxx>
>

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel