Re: [PATCH v3 05/10] x86/MSI: track host and guest masking separately

["Li, Liang Z" <liang.z.li@intel.com>]

> >>> On 01.04.16 at 09:40, <liang.z.li@intel.com> wrote:
> > A couple of weeks ago, Jianzhong reported an issue, the SRIOV NICs
> > (Intel 82599, 82571 ) can't work correctly in Windows guest.
> > By debugging, we found your this patch, the commit ID
> > ad28e42bd1d28d746988ed71654e8aa670629753,  caused the regression.
> 
> That was obvious.
> 
> > Could you help to take a look which part of your change lead to the
> > regression?
> > The SRIOV NICs works well in Linux guest.
> 
> As you may have seen, I've already found and fixed one aspect.
> I'm in the process of fixing another because, no, SRIOV NICs do not work well
> in Linux guests, at least not in recent ones (first noticed in 4.4, but last time I
> had tried before was with 4.0 I think) with CONFIG_XEN off.
> 
> Beyond that I guess I could use some help in at least diagnosing the issue, e.g.
> by logging the actions done by Xen, so we can understand why
> guest_mask_msi_irq() doesn't get called to unmask the MSI-X vector(s). I've
> found the reason why this isn't happening on Linux, and I am testing a
> possible fix. However, from the logs I've seen so far for Windows (with older

Glad to hear that you are working on this. Thanks!

> Xen, and with the above mentioned fix
> backported) it is already clear that this change won't help there (unless of
> course the issue you see is Windows version dependent).

> And just to be clear - the change previously proposed by Jianzhong is still not
> going to be an option: We need to understand and address the root cause of
> the issue, not paper over it by guessing when to unmask interrupts.
> 

Totally agree.

Liang
> Jan


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