Re: [Xen-devel] [PATCH RFC] xen/pvh: use a custom IO bitmap for PVH hardware domains

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

El 08/04/15 a les 14.57, Roger Pau Monne ha escrit:
> Since a PVH hardware domain has access to the physical hardware create a
> custom more permissive IO bitmap. The permissions set on the bitmap are
> populated based on the contents of the ioports rangeset.
> 
> Also add the IO ports of the serial console used by Xen to the list of not
> accessible IO ports.

I have one question about the current IO port handling for PVH guests
(DomU and Dom0). There's some code right now in vmx_vmexit_handler
(EXIT_REASON_IO_INSTRUCTION) that's kind PVH specific:

if ( exit_qualification & 0x10 )
{
    /* INS, OUTS */
    if ( unlikely(is_pvh_vcpu(v)) /* PVH fixme */ ||
         !handle_mmio() )
        hvm_inject_hw_exception(TRAP_gp_fault, 0);
}
else
{
    /* IN, OUT */
    uint16_t port = (exit_qualification >> 16) & 0xFFFF;
    int bytes = (exit_qualification & 0x07) + 1;
    int dir = (exit_qualification & 0x08) ? IOREQ_READ : IOREQ_WRITE;

    if ( handle_pio(port, bytes, dir) )
        update_guest_eip(); /* Safe: IN, OUT */
}

Is there any need for DomUs to access the IO ports? I know that FreeBSD
will poke at some of them during boot to scan for devices, but I'm not
sure if we could just make them noops in the PVH case and simply return
garbage.

Also, once this is set the PVH Specification document should be updated
to reflect what can guests expect when poking at IO ports.

Roger.

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