From: Sean Christopherson <seanjc@google.com>
To: Jann Horn <jannh@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
David Woodhouse <dwmw@amazon.co.uk>,
kernel list <linux-kernel@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>,
Michal Hocko <mhocko@suse.com>
Subject: Re: KVM nonblocking MMU notifier with KVM_GUEST_USES_PFN looks racy [but is currently unused]
Date: Mon, 18 Sep 2023 11:07:44 -0700 [thread overview]
Message-ID: <ZQiR8IpqOZrOpzHC@google.com> (raw)
In-Reply-To: <CAG48ez0YBOUGnj+N_MBp2WCvp0BLk1o7n6uSH2nrj1z-qgf+0A@mail.gmail.com>
On Mon, Sep 18, 2023, Jann Horn wrote:
> Hi!
>
> I haven't tested this and might be missing something, but I think that
> the MMU notifier for KVM_GUEST_USES_PFN pfncache is currently a bit
> broken. Except that nothing seems to actually use KVM_GUEST_USES_PFN,
> so currently it's not actually a problem?
Yeah, the implementation is busted, and IMO the entire concept is a dead-end[1].
David Steven's series[2] doesn't actually rip out KVM_GUEST_USES_PFN, I'll add
that to the todo list. There are no users, and I don't expect any to come along,
precisely because it's busted :-)
[1] https://lore.kernel.org/all/ZBEEQtmtNPaEqU1i@google.com
[2] https://lkml.kernel.org/r/20230911021637.1941096-1-stevensd%40google.com
prev parent reply other threads:[~2023-09-18 18:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-18 17:12 KVM nonblocking MMU notifier with KVM_GUEST_USES_PFN looks racy [but is currently unused] Jann Horn
2023-09-18 18:07 ` Sean Christopherson [this message]
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