Received-SPF: pass (google.com: domain of linux-kernel+bounces-54231-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Date: Mon, 5 Feb 2024 19:02:42 -0800
In-Reply-To: <CAD=HUj62vdy9CmqHWsAQi4S6i1ZH8uUE81p8Wu67pQd5vNRr+w@mail.gmail.com>
Precedence: bulk
Mime-Version: 1.0
References: <20230911021637.1941096-1-stevensd@google.com> <20230911021637.1941096-7-stevensd@google.com>
 <14db8c0b-77de-34ec-c847-d7360025a571@collabora.com> <CAD=HUj62vdy9CmqHWsAQi4S6i1ZH8uUE81p8Wu67pQd5vNRr+w@mail.gmail.com>
Message-ID: <ZcGhUvUuiK090tcq@google.com>
Subject: Re: [PATCH v9 6/6] KVM: x86/mmu: Handle non-refcounted pages
From: Sean Christopherson <seanjc@google.com>
To: David Stevens <stevensd@chromium.org>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>, Yu Zhang <yu.c.zhang@linux.intel.com>, 
	Isaku Yamahata <isaku.yamahata@gmail.com>, Zhi Wang <zhi.wang.linux@gmail.com>, 
	kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable

On Tue, Sep 19, 2023, David Stevens wrote:
> On Mon, Sep 18, 2023 at 6:58=E2=80=AFPM Dmitry Osipenko
> <dmitry.osipenko@collabora.com> wrote:
> >
> > On 9/11/23 05:16, David Stevens wrote:
> > > From: David Stevens <stevensd@chromium.org>
> > >
> > > Handle non-refcounted pages in __kvm_faultin_pfn. This allows the hos=
t
> > > to map memory into the guest that is backed by non-refcounted struct
> > > pages - for example, the tail pages of higher order non-compound page=
s
> > > allocated by the amdgpu driver via ttm_pool_alloc_page.
> > >
> > > The bulk of this change is tracking the is_refcounted_page flag so th=
at
> > > non-refcounted pages don't trigger page_count() =3D=3D 0 warnings. Th=
is is
> > > done by storing the flag in an unused bit in the sptes. There are no
> > > bits available in PAE SPTEs, so non-refcounted pages can only be hand=
led
> > > on TDP and x86-64.
> > >
> > > Signed-off-by: David Stevens <stevensd@chromium.org>
> > > ---
> > >  arch/x86/kvm/mmu/mmu.c          | 52 +++++++++++++++++++++++--------=
--
> > >  arch/x86/kvm/mmu/mmu_internal.h |  1 +
> > >  arch/x86/kvm/mmu/paging_tmpl.h  |  8 +++--
> > >  arch/x86/kvm/mmu/spte.c         |  4 ++-
> > >  arch/x86/kvm/mmu/spte.h         | 12 +++++++-
> > >  arch/x86/kvm/mmu/tdp_mmu.c      | 22 ++++++++------
> > >  include/linux/kvm_host.h        |  3 ++
> > >  virt/kvm/kvm_main.c             |  6 ++--
> > >  8 files changed, 76 insertions(+), 32 deletions(-)
> >
> > Could you please tell which kernel tree you used for the base of this
> > series? This patch #6 doesn't apply cleanly to stable/mainline/next/kvm
> >
> > error: sha1 information is lacking or useless (arch/x86/kvm/mmu/mmu.c).
> > error: could not build fake ancestor
>=20
> This series is based on the kvm next branch (i.e.
> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=3Dnext). The
> specific hash is d011151616e73de20c139580b73fa4c7042bd861.

Drat, found this too late.  Please use --base so that git appends the exact=
 base
commit.   From Documentation/process/maintainer-kvm-x86.rst:

Git Base
~~~~~~~~
If you are using git version 2.9.0 or later (Googlers, this is all of you!)=
,
use ``git format-patch`` with the ``--base`` flag to automatically include =
the
base tree information in the generated patches.

Note, ``--base=3Dauto`` works as expected if and only if a branch's upstrea=
m is
set to the base topic branch, e.g. it will do the wrong thing if your upstr=
eam
is set to your personal repository for backup purposes.  An alternative "au=
to"
solution is to derive the names of your development branches based on their
KVM x86 topic, and feed that into ``--base``.  E.g. ``x86/pmu/my_branch_nam=
e``,
and then write a small wrapper to extract ``pmu`` from the current branch n=
ame
to yield ``--base=3Dx/pmu``, where ``x`` is whatever name your repository u=
ses to
track the KVM x86 remote.