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[34.127.9.76]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b9cae4a127sm5909845ad.67.2026.04.30.13.36.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2026 13:36:40 -0700 (PDT) Date: Thu, 30 Apr 2026 20:36:36 +0000 From: David Matlack To: Vipin Sharma Cc: iommu@lists.linux.dev, kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Joerg Roedel , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Robin Murphy , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Will Deacon , William Tu , Yi Liu Subject: Re: [PATCH v4 02/11] PCI: liveupdate: Track outgoing preserved PCI devices Message-ID: References: <20260423212316.3431746-1-dmatlack@google.com> <20260423212316.3431746-3-dmatlack@google.com> <20260428201231.GA3885809.vipinsh@google.com> <20260430175916.GA13902.vipinsh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260430175916.GA13902.vipinsh@google.com> X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2C3751C0009 X-Stat-Signature: 1663iupsxsb48cbti94ry8e6tqn1rqfh X-HE-Tag: 1777581402-344855 X-HE-Meta: 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 lecbVXIU E5wqmXcXN+8d+kV/ow1BcxWPjbS0hIJ/9f2P3LKH+zZSsKP2VwcREisBFj55Z0fFtEjjhuzB6VKuwe3CeDs3U62P4+hI453rzIGpOeFv6EILUsdhVywtmXy7FO61ZA8aUq+o2x99fFpp2AtPsRWEwNj79wSQxeKnUcX0T7DAX74nM1JN7woI/rQB28clDsO1ivKt2JwNIkBNI5h9NbTsRSYgjzWavCbvji/yDx5OqX8x84DZsROSS4UquHAAHydb3CpihSmfewn1DtdmsSQYkyQqkA8LQT6/1Ma5gSJcRiP8z9Xkpw7cDdu+gg17FWI18daqLIyWt3elY32J0PvtwfR/bk+XD3sGwfRkmSniKdq0N5B5Gxgb2ONs11A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-04-30 11:25 AM, Vipin Sharma wrote: > On Tue, Apr 28, 2026 at 02:12:13PM -0700, David Matlack wrote: > > On Tue, Apr 28, 2026 at 1:20 PM Vipin Sharma wrote: > > > > > > On Thu, Apr 23, 2026 at 09:23:06PM +0000, David Matlack wrote: > > > > +int pci_liveupdate_preserve(struct pci_dev *dev) > > > > +{ > > > > + if (ser->nr_devices == ser->max_nr_devices) > > > > + return -ENOSPC; > > > > + > > > > + for (i = 0; i < ser->max_nr_devices; i++) { > > > > + /* > > > > + * Start searching at index ser->nr_devices. This should result > > > > + * in a constant time search under expected conditions (devices > > > > + * are not getting unpreserved). > > > > + */ > > > > + int index = (ser->nr_devices + i) % ser->max_nr_devices; > > > > + struct pci_dev_ser *dev_ser = &ser->devices[index]; > > > > + > > > > + if (dev_ser->refcount) > > > > + continue; > > > > + > > > > + pci_info(dev, "Device will be preserved across next Live Update\n"); > > > > + ser->nr_devices++; > > > > + > > > > + dev_ser->domain = pci_domain_nr(dev->bus); > > > > + dev_ser->bdf = pci_dev_id(dev); > > > > + dev_ser->refcount = 1; > > > > + > > > > + dev->liveupdate_outgoing = dev_ser; > > > > + return 0; > > > > + } > > > > + > > > > + return -ENOSPC; > > > > > > Since it is executing under a mutex, and we already failed > > > 'if (ser->nr_devices == ser->max_nr_devices) check above, will we ever reach > > > here and return -ENOSPC? > > > > Yeah I wouldn't expect to ever reach here. > > Will you be removing it or want to keep it just in case scenario? I'm not sure how I would remove it. The code doesn't not compile without a return.