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Wed, 28 Oct 2026 08:41:01 -0700 (PDT) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 References: <20261027025616.1632690-1-kevinloughlin@google.com> <20261027025616.1632690-11-kevinloughlin@google.com> <2976bc2d-2642-4448-9c1f-ec13e67e45d5@kernel.org> In-Reply-To: <2976bc2d-2642-4448-9c1f-ec13e67e45d5@kernel.org> From: Kevin Loughlin Date: Wed, 28 Oct 2026 08:40:47 -0700 X-Gm-Features: AclHuK9oWsApJE-SwbWIqUTDRpRi_a-FG1r_BRCTB7JJ3QabTlKp_kjVIFg_bKo Message-ID: Subject: Re: [PATCH 10/13] virtio_balloon: add higher-order page inflation To: "David Hildenbrand (Arm)" Cc: "Michael S. Tsirkin" , Jason Wang , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Xuan Zhuo , Ard Biesheuvel , Kiryl Shutsemau , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Tom Lendacky , Ashish Kalra , Michael Roth , Rick Edgecombe , Andrew Morton , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Alexander Duyck , virtualization@lists.linux.dev, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sidharth Telang , Punit Salian , Peter Gonda , Ackerley Tng , Jacky Li , Steve Rutherford , David Skidmore Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Oct 28, 2026 at 1:59=E2=80=AFAM David Hildenbrand (Arm) wrote: > > On 10/27/26 03:56, Kevin Loughlin wrote: > > In confidential computing guests requiring page state transitions, > > unaccepted memory tracking operates at the EFI unaccepted memory unit > > granularity (typically 2MB / order 9 on x86). Inflating the balloon > > with 4KB pages would prevent unaccepting the backing 2MB unit. > > > > Inflate balloon pages at unaccepted_memory_order() when > > virtballoon_cc_needs_state_transition() is true, while retaining > > order-0 allocations for non-CoCo guests and CoCo guests that do not > > use unaccepted memory transitions. When a higher-order balloon page > > spans more 4KB balloon PFNs than VIRTIO_BALLOON_ARRAY_PFNS_MAX (256), > > transmit its PFNs to the host in VIRTIO_BALLOON_ARRAY_PFNS_MAX chunks. > > > > Signed-off-by: Kevin Loughlin > > Sorry, not happening. There is no migration support for these (large) thi= ngs, > and there likely won't be any time soon. > > NAK Yeah, you're right. Another great reason to abandon the inflate/deflate aspect of this series beyond what Michael pointed out. I will follow up on the cover letter RE: how doing so might provide a path forward for the CoCo free page reporting by simplifying things.