Re: WARNING trace at kvm_nx_huge_page_recovery_worker on 6.3.4

[Sean Christopherson <seanjc@google.com>]

On Tue, May 30, 2023, Fabio Coatti wrote:
> Il giorno dom 28 mag 2023 alle ore 14:44 Bagas Sanjaya
> <bagasdotme@gmail.com> ha scritto:
> > #regzbot ^introduced: v6.3.1..v6.3.2
> > #regzbot title: WARNING trace at kvm_nx_huge_page_recovery_worker when opening a new tab in Chrome
> 
> Out of curiosity, I recompiled 6.3.4 after reverting the following
> commit mentioned in 6.3.2 changelog:
> 
> commit 2ec1fe292d6edb3bd112f900692d9ef292b1fa8b
> Author: Sean Christopherson <seanjc@google.com>
> Date:   Wed Apr 26 15:03:23 2023 -0700
> KVM: x86: Preserve TDP MMU roots until they are explicitly invalidated
> commit edbdb43fc96b11b3bfa531be306a1993d9fe89ec upstream.
> 
> And the WARN message no longer appears on my host kernel logs, at
> least so far :)

Hmm, more than likely an NX shadow page is outliving a memslot update.  I'll take
another look at those flows to see if I can spot a race or leak.

> > Fabio, can you also check the mainline (on guest)?
> 
> Not sure to understand, you mean 6.4-rcX? I can do that, sure, but why
> on guest?

Misunderstanding probably?  Please do test with 6.4-rcX on the host.  I expect
the WARN to reproduce there as well, but if it doesn't then we'll have a very
useful datapoint.