Re: [Xen-devel] Failed to access register with invalid access size alignment

["Zytaruk, Kelly" <Kelly.Zytaruk@xxxxxxx>]

> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Friday, April 04, 2014 10:00 AM
> To: Zytaruk, Kelly
> Cc: Xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Failed to access register with invalid access size
> alignment
> 
> On Wed, Apr 02, 2014 at 07:28:44PM +0000, Zytaruk, Kelly wrote:
> > I have seen the subject-line error message in a few posts but I haven't yet 
> > seen
> a resolution for it yet.  Has anyone resolved this problem?
> >
> > The full error line from the log file is; [00:05.0]
> > xen_pt_pci_config_access_check: Error: Failed to access register with
> > invalid access size alignment. (addr: 0x0e, len: 4)
> >
> 
> You could instrument QEMU to pause the guest immediately when this happens.

Do you mean simply keeping QEMU in a while loop and not processing any more 
events when this happens like doing

    /* check offset alignment */
    if (address & (len-1))
    {
        PT_LOG_DEV(d, "Error: Failed to read register with invalid access size "
            "alignment. [Offset:%02xh][Length:%d]\n", address, len);
        stay_in_loop = true;
-->     while (stay_in_loop)  usleep (1000);   <--
        goto exit;
    }

or is there a more "elegant" way to pause the guest.

> Then you can use xen_hvmtrace to figure the EIP and get an idea of where
> things are.
> 

I googled "hvmtrace" and found a few code submissions but didn't find any 
information on how to use it.  Is there any documentation?


> > Address 0x0e in PCIe config space is 2 byte aligned and can't be accessed 
> > as a
> 4 byte read.
> >
> > I am passing an AMD graphics adapter into a guest as a secondary adapter.  I
> can connect with VNC and the PCI passthrough is successful as I can see the
> [00:05.0] device in Win7 device Manager but the device is "banged out" with 
> the
> error "Windows has stopped this device because it has reported problems. (Code
> 43)".
> >
> > The error occurs with both QEMU-upstream and QEMU-traditional.
> > My configuration is Xen 4.5-unstable on Linux 3.13.4.
> >
> > Thanks,
> > Kelly
> >
> >
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel


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