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[129.46.96.20]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d5866269a8sm4324502a34.13.2026.02.27.06.06.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Feb 2026 06:06:57 -0800 (PST) From: Yuvraj Sakshith To: akpm@linux-foundation.org Cc: mst@redhat.com, david@kernel.org, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v1 0/4] Allow order zero pages in page reporting Date: Fri, 27 Feb 2026 06:06:51 -0800 Message-Id: <20260227140655.360696-1-yuvraj.sakshith@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: RwBguJgnWIADgmgr2yQsAdPmCkWutPlA X-Authority-Analysis: v=2.4 cv=Vtouwu2n c=1 sm=1 tr=0 ts=69a1a505 cx=c_pps a=7uPEO8VhqeOX8vTJ3z8K6Q==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_K5XuSEh1TEqbUxoQ0s3:22 a=9ecvtSpfVrh-a2M179QA:9 a=EXS-LbY8YePsIyqnH6vw:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjI3MDEyNSBTYWx0ZWRfX6+uU95D5Vg4u /ynAh/rSYxT6REGrdF7iENQC107D3rspy5PbLMXUjP1tXcSc80nxgv6h6xUpvh6eOln5SZ1faZn wacC8ZoH+nrkcVpLXPtZlkI2kFZrjLOB3HqadNAwbVdJ9xSzJgppHphd5AEMJlnNwJl4ZGE3oaT KyUobJh7lO/LAnB6tmMWdvy43w4QeEiEyfoVEIt9uYRbpmU2xPH6DEZAoqLzeyEpVDHu2U++Gy4 iD89hzOMEbB6DMgdGwIWRdSgiWIfR6xf7CGsaJeCtfoeOYt8kbEbZaLaQzIV4vusE4t+U/xQrmC 4i8yLYmq31Be/NDgulacJqsnEIyozDLHkWWmb7SlKqFY1HZL5Iz2k72QVmUSytwwaJ0pVBpdV5z YQyjMtC3M60amyY2mCkw95tY9+ClxF8AXH7sU/RwD+nmSwT19DxfEIrkjJLw1gDP0mMRhGRD3d0 CWbQVv5gy4d4OIt7d7Q== X-Proofpoint-GUID: RwBguJgnWIADgmgr2yQsAdPmCkWutPlA X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-27_02,2026-02-27_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 clxscore=1015 phishscore=0 bulkscore=0 spamscore=0 impostorscore=0 suspectscore=0 adultscore=0 malwarescore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2602270125 Today, page reporting sets page_reporting_order in two ways: (1) page_reporting.page_reporting_order cmdline parameter (2) Driver can pass order while registering itself. In both cases, order zero is ignored by free page reporting because it is used to set page_reporting_order to a default value, like MAX_PAGE_ORDER. In some cases we might want page_reporting_order to be zero. For instance, when virtio-balloon runs inside a guest with tiny memory (say, 16MB), it might not be able to find a order 1 page (or in the worst case order MAX_PAGE_ORDER page) after some uptime. Page reporting should be able to return order zero pages back for optimal memory relinquishment. This patch changes the default fallback value from '0' to '-1' in all possible clients of free page reporting (hv_balloon and virtio-balloon) together with allowing '0' as a valid order in page_reporting_register(). Changes in v1: - Introduce PAGE_REPORTING_DEFAULT_ORDER macro (initially set to 0). - Make use of new macro in drivers (hv_balloon and virtio-balloon) working with page reporting. - Change PAGE_REPORTING_DEFAULT_ORDER to -1 as zero is a valid page order that can be requested. Yuvraj Sakshith (3): mm/page_reporting: Allow zero page_reporting_order hv_balloon: Change default page reporting order virtio_balloon: Set pr_dev.order to new default drivers/hv/hv_balloon.c | 2 +- drivers/virtio/virtio_balloon.c | 14 ++++++++++++++ mm/page_reporting.c | 2 +- 3 files changed, 16 insertions(+), 2 deletions(-) -- 2.34.1