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[34.105.13.176]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b9cae55612sm4897165ad.73.2026.04.30.13.42.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2026 13:42:35 -0700 (PDT) Date: Thu, 30 Apr 2026 13:42:31 -0700 From: Vipin Sharma To: David Matlack 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: <20260430204009.GB22297.vipinsh@google.com> References: <20260423212316.3431746-1-dmatlack@google.com> <20260423212316.3431746-3-dmatlack@google.com> <20260428201231.GA3885809.vipinsh@google.com> <20260430175916.GA13902.vipinsh@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Apr 30, 2026 at 08:36:36PM +0000, David Matlack wrote: > 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. Oh, I meant, inside loop a break and outside just return 0, that way it won't be a dead code.