Re: x86: missing FRED #PF event data?

[Sergey Senozhatsky]

On (26/08/10 11:03), Peter Zijlstra wrote:
> > > > and got the following while running my tests (and well, we don't crash
> > > > anymore):
> > > > 
> > > > [  254.040223] :: fixed up address to ffff9c4d64af4000  [[fred: 0 cr2: ffff9c4d64af4000]]
> > > > ...
> > > > [ 1821.904563] :: fixed up address to ffff9c4e9dd0a000  [[fred: 0 cr2: ffff9c4e9dd0a000]]
> > > > 
> > > > Does any of this make sense to you?
> > > 
> > > I think the explanation is some pKVM shenanigans.  Sorry for the noise.
> > 
> > No, I think we are back at square one.  I thought that maybe pKVM
> > was disabling FRED and that was causing issues.  But I actually see
> > that both cpu_feature_enabled(X86_FEATURE_FRED) and (cr4 & X86_CR4_FRED)
> > claim FRED is enabled, yet fred #PF data is 0 while CR2 holds the correct
> > address.
> 
> Can you reproduce on real hardware? I mean, you were babbling about pKVM
> (whatever that is), so I'm thinking you're on some dodgy virt thing.
> 
> Not that I have any actual FRED hardware to test anything on :/

It's an actual H/W, a laptop (Intel(R) Core(TM) Ultra 7 355 powered),
I was babbling about pKVM because it seems that the best way to
reproduce is to launch a VM, yet the crash is happening on the host
side.