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Tue, 6 Oct 2026 03:01:22 +0000 (GMT) Received: from [9.124.213.110] (unknown [9.124.213.110]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 6 Oct 2026 03:01:22 +0000 (GMT) Message-ID: Date: Tue, 6 Oct 2026 08:31:21 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] KVM: PPC: Book3S HV: Add preempt_disable() around virtual-mode HPTE bit-lock users To: Madhavan Srinivasan , linuxppc-dev@lists.ozlabs.org, Nicholas Piggin , Michael Ellerman , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Gautam Menghani , Harsh Prateek Bora , R Nageswara Sastry , Alexander Graf , linux-hardening@vger.kernel.org, stable@vger.kernel.org, Avi Kivity References: <20260930173750.56759-1-amachhiw@linux.ibm.com> <20260930173750.56759-3-amachhiw@linux.ibm.com> <20261005234024.20213ac7-78-amachhiw@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20261005234024.20213ac7-78-amachhiw@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDA2MDAxMCBTYWx0ZWRfXzIrFcDKLio3b BtZ3WnKhtuvm4VaRvPi6Wie5XaRznTT0C4ZrSYmlw1BjODD35oz20abNC73QeQWl1IBs/CWJMnk 5b0YZPPYStB/RzoQ8VwlZWtQOSb0RWA= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDA2MDAxMCBTYWx0ZWRfX7p5qNES/zKzv auvGdkZCWOjqQCSx34p89Er0CvI62GP34su8OZu2VPgudAljoZq9sqeiVYPIZxJ3AbYM8MrReAJ yJJp16O9X7Rzf7lcoIHbPU2Q9da3TbDu0qfEINzCm3TdMFB6Tsj4pP3DK/xTpdeufvBdxBIdTen 8HponTRZ7OMfaNH5MW8at3yjVNt4rkmrhJql4KllBziT9vgQjL7cnKhte7heobTQ7BucybLMUtU JcPwTyDxnCmstPqd41G3M70OFyR/3ngHSzlKRmAzu0+ke9G/COTEflkymfaPmQ7ND2sqlBmbtLy 8DmytLwXu8US63695zTOLUB0JraY2LrKjWvBVtRR7MynX5AIS/65CxDvL3lG4/3lTSSxkVz3r54 OFEwlLK942v/3mkF5WOCU6xGzVo1kZz67bA/TqaBdGFqOB2ywtCQYImF4QxCk/72+DoASp7c8G+ BBmtKXBnlYZwXCld5PA== X-Proofpoint-GUID: 3OSaq9WWDPw38Y2gOSJIk5gwPyhZqYCz X-Proofpoint-ORIG-GUID: qeSoUgWU6eepVwJoT9V5pStS7Vlo_yhX X-Authority-Analysis: v=2.4 cv=B7osQ+tM c=1 sm=1 tr=0 ts=6ac4648b cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=anADAJyGIn8O9P3fJOYA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-05_05,2026-10-05_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 malwarescore=0 impostorscore=0 phishscore=0 clxscore=1015 spamscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610060010 On 10/5/26 11:57 PM, Amit Machhiwal wrote: > Hi Shrikanth, > > Thanks for the review. Please find my responses inline below. > >> I don't like this sprinkling of preempt disable/enable. >> Is there not a way to embedd this in try_lock_hpte/unlock_hpte? > > I understand the scattering of preempt_disable()/preempt_enable() looks ugly. > But there are two blockers for that approach: > > 1. The real-mode hcall dispatch table (hcall_real_table in > book3s_hv_rmhandlers.S) calls kvmppc_h_enter(), kvmppc_h_remove(), > kvmppc_h_bulk_remove() and others in book3s_hv_rm_mmu.c, which all call > try_lock_hpte() from real mode. Adding preempt_disable() inside > try_lock_hpte() would affect those real-mode callers, which brings us to your > second point. > Fair enough. Reviewed-by: Shrikanth Hegde