linux-kernel - Re: [PATCH 2/2] selftests: KVM: Add page splitting test

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Date:   Fri, 20 Jan 2023 12:04:04 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     Ricardo Koller <ricarkol@...gle.com>
Cc:     David Matlack <dmatlack@...gle.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vipin Sharma <vipinsh@...gle.com>
Subject: Re: [PATCH 2/2] selftests: KVM: Add page splitting test

On Fri, Jan 20, 2023 at 6:34 AM Ricardo Koller <ricarkol@...gle.com> wrote:
>
...
> > > > > +
> > > > > +     run_test(&p);
> > > >
> > > > Use for_each_guest_mode() to run against all supported guest modes.
> > >
> > > I'm not sure that would actually improve coverage. None of the page
> > > splitting behavior depends on the mode AFAICT.
> >
> > You need to use for_each_guest_mode() for the ARM case. The issue is
> > that whatever mode (guest page size and VA size) you pick might not be
> > supported by the host. So, you first to explore what's available (via
> > for_each_guest_mode()).
>
> Actually, that's fixed by using the default mode, which picks the
> first available
> mode. I would prefer to use for_each_guest_mode() though, who knows and
> something fails with some specific guest page size for some reason.

Okay, will do. I wasn't sure if we did eager page splitting on ARM, so
I was only planning on making this test for x86_64 initially, hence it
being in that directory. If ARM rolls with the same behavior, then
I'll add the for_each_mode bit and move the test up a directory.

>
> >
> > Thanks,
> > Ricardo
> >
> > >
> > > >
> > > > > +
> > > > > +     return 0;
> > > > > +}
> > > > > --
> > > > > 2.39.1.405.gd4c25cc71f-goog
> > > > >