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[129.46.96.20]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-67a1d603f31sm938666eaf.5.2026.03.03.01.33.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2026 01:33:43 -0800 (PST) From: Yuvraj Sakshith To: mst@redhat.com, david@kernel.org Cc: 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, akpm@linux-foundation.org, 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, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org Subject: [PATCH v3 0/5] Allow order zero pages in page reporting Date: Tue, 3 Mar 2026 01:33:36 -0800 Message-Id: <20260303093341.2927482-1-yuvraj.sakshith@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzAzMDA3MSBTYWx0ZWRfX67jYeIfQHqH4 ocA7Z03BnzbEl6UKBuAuuqMzSRu+5iZ0Gps9wb9M764ssEfMGXi8VvvQUM7eMZ6rKB+V9RW4+PQ JRxYb8cpU3/2AaE7UPCiSDHhTJ90dMChwVlwYJndOmY2lwTi4Q8Qt+k7onKy/trK42vUsQPCvjo Qyf76YjzZ0trDgY+XSR8H8tGgPF7sSv4CEOX81CYF0x+w3T2ftfLxGr3NkrcbBTC/PzDdCldZci S1pYfDNIO8hS+XE6/1oTC3vyEHQ5d689VHyqKKvlZtUvPRKXA+GJB0hpDgr6chfbsyc5BVINNtt gBAxfbDfbAvFlY9VNtNGMWm/A0yff3WuGa92lXSkN4WBYMUh31yL87USoAaZDmQHl8U/vBo1TC8 AOFCqwjBVBFecha5v0+qtarSn6GVjzNSzNpBj3SUVd+ebgqhHIfNEe/7b2rofY8UdVcDuhEOvDH 0ZN4oQT5352i9I69phA== X-Authority-Analysis: v=2.4 cv=MuhfKmae c=1 sm=1 tr=0 ts=69a6aaf9 cx=c_pps a=7uPEO8VhqeOX8vTJ3z8K6Q==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_K5XuSEh1TEqbUxoQ0s3:22 a=HYTG7BDJ-qdBC1FqdxkA:9 a=EXS-LbY8YePsIyqnH6vw:22 X-Proofpoint-ORIG-GUID: NENRQZolKdQy8zV-g6FS5rkj1xfJqvGN X-Proofpoint-GUID: NENRQZolKdQy8zV-g6FS5rkj1xfJqvGN 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=2026-03-02_05,2026-03-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 impostorscore=0 suspectscore=0 malwarescore=0 clxscore=1015 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603030071 X-Rspam-User: X-Rspamd-Queue-Id: 897D61C0004 X-Rspamd-Server: rspam08 X-Stat-Signature: zsdg14wktprgt6c4paspp9ftme4b5y1s X-HE-Tag: 1772530426-369575 X-HE-Meta: U2FsdGVkX18IQeXxk0CuqkdOMU+spvqNM2m7yD8aNJrRIAt8RJtNIplo8gEOn4x/SsvyotUn1zuscIoDLAQULjJ5tj7QOYLwHezjwnEDotW80798k6+gi+mpz91PSgGRQYBk6YwTWSTD6kW4YeUvOaFFEAAMG+d3FeDqAjpW4YVmSeMeN0BD4w0G/ct7A0yea81u6RlT9KU9qIkPmZPCIwEnpFiVO1HDY2E+lniqQVHxMF2aebO7pSh1Oo2jFyPJFzZULYjcGhxsPkP1vK1edNCv7GevkgP75Dma9Ton8mq77Dh0yhhNJAZqtt0irZa5ncg38PCXmcZ/ke0MSn/4gvxRjgxqnIsy/fX5nX8gEI/SqKmNipWwWVTBJwbOagE9ukcvU18wZFqdB2ESH8hMwY3jOf/OEYPcIrCS4fGWm3SHTSAQSbTiK6fUVeu3CcEUDKEJgZh6xAsjyHKOyfKLYz1pQniiF8bl7ZGbNAgbcaMwwwkGXkdQawLkq+T1dKKJo21WXBFK0g4URLmYag3CRL6ry7gDVfF0jlDcRregQVXJ9k5XFWa2RczVLvif8/FPRAbyofaqqrVzpC5tugaYQiNBacNvHeyNJXkJ9dlqfg+NVfd/tS9Cjkq9EToILFel+6iKpLpgI2LeNIbu1wf0imA4HQEQuEWSJ1x/dshQzsHjdBiIGpIvVfpCsxqgqxexQLRFevyOUEupH707+DVqebQIKh6KqCQIDixR8DHIktiVf7RZ3VH/NXXv2/AkVCPOh3AUuG4+zSerPfL9j67E18ipONKViR0bB34dYINP0f2tqAnCeRe/cu9FmDq6mfUc5FPMHcQG4ptF6tHLLrjqtrX+kkbPeJMfYmzYu5GimbHNZTfnUM+jKBRknT1GURUtCEDpuOLZsjVZAG0xn3PQGrdgKClPMnPLrVLe1z+izI1vFO354RCBvh7KK5AVrgXRM758Ikd65i7kiAEfbyb 5M/bNtjf Gh/C/1ISbW/uwD/0JiF1jZF5Pd0PzsLDeTrJvCPIbWZtyILhpgjFhdY1FAtrmiUXvYUjsUxjDw/h9avq8LW8fKUkJwwP9Nlm+QUvN+UqwRwY62tZrMjz5ZXKqEMGY/GbONytVRUMv2guIuUuEZEw+sTtQYxjEPSDRug2sDO7c0ZkP5g4qAD1oXl92GrAfPHULg/nt Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Changes in v2: - Better naming. Replace PAGE_REPORTING_DEFAULT_ORDER with PAGE_REPORTING_ORDER_UNSPECIFIED. This takes care of the situation where page reporting order is not specified in the commandline. - Minor commit message changes. Changes in v3: - Setting page_reporting_order's initial value to PAGE_REPORTING_ORDER_UNSPECIFIED moved to PATCH #5. Yuvraj Sakshith (5): mm/page_reporting: add PAGE_REPORTING_ORDER_UNSPECIFIED virtio_balloon: set unspecified page reporting order hv_balloon: set unspecified page reporting order mm/page_reporting: change PAGE_REPORTING_ORDER_UNSPECIFIED to -1 mm/page_reporting: change page_reporting_order to PAGE_REPORTING_ORDER_UNSPECIFIED drivers/hv/hv_balloon.c | 2 +- drivers/virtio/virtio_balloon.c | 2 ++ include/linux/page_reporting.h | 1 + mm/page_reporting.c | 7 ++++--- 4 files changed, 8 insertions(+), 4 deletions(-) -- 2.34.1