Re: [Xen-devel] Issues with PCI-Passtrough (VT-d) in HVM with Xen 4.6

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.06.16 at 21:59, <syso@xxxxxxxxxxxxx> wrote:
> Temporary Fix
> -------------
> 
> After checking the source[1] of the PCI configuration space
> handling in xen-pciback, I found out that changing line 258
> to read
> 
>     if (handled && !err) {
> 
> instead of:
> 
>     if (!handled && !err) {
> 
> solves the issue and I can successfully write to the interface.

This can't possibly a solution (see also the comment right there). But
without you telling us what register gets written with what value,
and what's being read back, I don't think there's much we can do or
suggest. In the end, by changing the conditional you force writes
that _did_ get emulated to _nevertheless_ also get carried out to
raw hardware. If that helps for your specific case, then it's quite
possible that something in the emulation paths invoked from the
code above that conditional is wrong.

Jan




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