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Tue, 16 Sep 2025 17:36:45 +0000 (GMT) Date: Tue, 16 Sep 2025 19:36:44 +0200 From: Heiko Carstens To: Christian Borntraeger Cc: Claudio Imbrenda , kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, nsg@linux.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, schlameuss@linux.ibm.com, svens@linux.ibm.com, agordeev@linux.ibm.com, david@redhat.com, gerald.schaefer@linux.ibm.com Subject: Re: [PATCH v2 08/20] KVM: s390: KVM page table management functions: allocation Message-ID: <20250916173644.27229Kcc-hca@linux.ibm.com> References: <20250910180746.125776-1-imbrenda@linux.ibm.com> <20250910180746.125776-9-imbrenda@linux.ibm.com> <20250916162653.27229G04-hca@linux.ibm.com> <20250916184737.47224f56@p-imbrenda> <63e8c905-28b1-4e1f-be77-e0789bd75692@de.ibm.com> <20250916190514.1a3082bd@p-imbrenda> <15f451d9-ecb3-4a82-9b9a-2de64b93944d@de.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <15f451d9-ecb3-4a82-9b9a-2de64b93944d@de.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 6Gu3lOm8AHS-3R8C-G1m7UJPuKzXB--7 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTE1MDAyOCBTYWx0ZWRfX6V/RQNCp2U6K ryv1ye8MSJ/mCs4FvCxFEwFzwqvwt37VY5wq6HXOv/NUDe18X3mzdLThc2V3vxb0RIn3qPLiWOs 2URJZ4izd5vxEgHxlEPg4blLnzDV1WfxnrJ9BVe+p1FPWrVHBIv3fvgveGVpEUqwIsUv69E9atv WoRlTbHA6UJgWEVjVtC/leqq0U6zpI/aovmy0uvzVWXbTTIoPXM11UKNno1xWEvUJV9IDBMAd7H ujgsF12bpyxILb5o7WxOqs8PyZUBRXJreLN3Mnk1xq8qNHwj/loV7XYH1VJcjcjDtGE03nFTU7b 4yBuo5/NMC8sdej9wWNJAzEJiGoE1RN2gS2O1NW5Y7SeIx0VLJ+byY5Q8Xgj3MCYl+bGig16gFM pGzwfl1Q X-Authority-Analysis: v=2.4 cv=HecUTjE8 c=1 sm=1 tr=0 ts=68c9a033 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=kj9zAlcOel0A:10 a=yJojWOMRYYMA:10 a=07d9gI8wAAAA:8 a=pldl6WKZccRfTaVWpKkA:9 a=CjuIK1q_8ugA:10 a=e2CUPOnPG4QKp8I52DXD:22 X-Proofpoint-GUID: 6Gu3lOm8AHS-3R8C-G1m7UJPuKzXB--7 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-16_02,2025-09-12_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 spamscore=0 priorityscore=1501 suspectscore=0 malwarescore=0 bulkscore=0 impostorscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509150028 On Tue, Sep 16, 2025 at 07:06:06PM +0200, Christian Borntraeger wrote: > > Am 16.09.25 um 19:05 schrieb Claudio Imbrenda: > > > > > I think GFP_ATOMIC actually gives more guarantees? > > > > > > In real life GFP_ATOMIC can fail, GFP_KERNEL does not.All gfp allocation failures > > > are usually the atomic ones. > > > > interesting... then I guess I need GFP_KERNEL | GFP_ATOMIC ? > > No. ATOMIC always means: can fail. So GFP_KERNEL alone is what is needed here. It is undocumented that small GFP_KERNEL allocations will never fail (retried for ever): https://lwn.net/Articles/627419/ https://lwn.net/Articles/723317/ While GFP_ATOMIC will fail e.g. if I/O is required to free up some memory.