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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Apr 04, 2014 at 02:33:55PM +0000, Zytaruk, Kelly wrote:
> 
> 
> > -----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.

Invoke the  xc_domain_pause function.

> 
> > 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?

Try /usr/lib64/bin/xen/xenctx [it might be in a different location depending
on how you built Xen]
> 
> 
> > > 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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