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Thu, 23 May 2024 14:38:42 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGifk9d+MfD2AFHnMnI801S7v/LhgxyOOXqYOMCa4unB24dBRc47U2Lkk9AateT6dg+Xjo3Eg== X-Received: by 2002:a6b:7e43:0:b0:7da:4135:89be with SMTP id ca18e2360f4ac-7e8c6c183aamr76817639f.17.1716500322062; Thu, 23 May 2024 14:38:42 -0700 (PDT) Received: from redhat.com ([38.15.36.11]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4b03e8281b1sm66737173.13.2024.05.23.14.38.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 May 2024 14:38:41 -0700 (PDT) Date: Thu, 23 May 2024 15:38:39 -0600 From: Alex Williamson To: Dan Williams Cc: Dave Jiang , , , , , , , , , Subject: Re: [PATCH v6 2/5] PCI: Add locking of upstream bridge for pci_reset_function() Message-ID: <20240523153839.16102e26.alex.williamson@redhat.com> In-Reply-To: <664fb286639ed_195e29416@dwillia2-mobl3.amr.corp.intel.com.notmuch> References: <20240502165851.1948523-1-dave.jiang@intel.com> <20240502165851.1948523-3-dave.jiang@intel.com> <20240523131005.5578e3de.alex.williamson@redhat.com> <664fb286639ed_195e29416@dwillia2-mobl3.amr.corp.intel.com.notmuch> X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 23 May 2024 14:17:58 -0700 Dan Williams wrote: > Alex Williamson wrote: > > On Thu, 2 May 2024 09:57:31 -0700 > > Dave Jiang wrote: > > > > > Fix a long standing locking gap for missing pci_cfg_access_lock() while > > > manipulating bridge reset registers and configuration during > > > pci_reset_bus_function(). Add calling of pci_dev_lock() against the > > > bridge device before locking the device. The locking is conditional > > > depending on whether the trigger device has an upstream bridge. If > > > the device is a root port then there would be no upstream bridge and > > > thus the locking of the bridge is unnecessary. As part of calling > > > pci_dev_lock(), pci_cfg_access_lock() happens and blocks the writing > > > of PCI config space by user space. > > > > > > Add lockdep assertion via pci_dev->cfg_access_lock in order to verify > > > pci_dev->block_cfg_access is set. > > > > > > Co-developed-by: Dan Williams > > > Signed-off-by: Dan Williams > > > Signed-off-by: Dave Jiang > > > --- > [..] > > > diff --git a/drivers/pci/access.c b/drivers/pci/access.c > > > index 6449056b57dd..36f10c7f9ef5 100644 > > > --- a/drivers/pci/access.c > > > +++ b/drivers/pci/access.c > > > @@ -275,6 +275,8 @@ void pci_cfg_access_lock(struct pci_dev *dev) > > > { > > > might_sleep(); > > > > > > + lock_map_acquire(&dev->cfg_access_lock); > > > + > > > raw_spin_lock_irq(&pci_lock); > > > if (dev->block_cfg_access) > > > pci_wait_cfg(dev); > > > @@ -329,6 +331,8 @@ void pci_cfg_access_unlock(struct pci_dev *dev) > > > raw_spin_unlock_irqrestore(&pci_lock, flags); > > > > > > wake_up_all(&pci_cfg_wait); > > > + > > > + lock_map_release(&dev->cfg_access_lock); > > > > > > This doesn't account for config access locks acquired via > > pci_cfg_access_trylock(), such as the pci_dev_trylock() through > > pci_try_reset_function() resulting in a new lockdep warning for > > vfio-pci when we try to release a lock that was never acquired. > > Thanks, > > Hey Alex, sorry about that, does this fix it up for you? Note I move the > lock_map_acquire() relative to the global pci_lock just for symmetry > purposes. Thanks, Dan! Yes, this fixes it. Please feel free to add Reported/Tested-by tags when you post it. Thanks! Alex > -- >8 -- > diff --git a/drivers/pci/access.c b/drivers/pci/access.c > index 30f031de9cfe..3595130ff719 100644 > --- a/drivers/pci/access.c > +++ b/drivers/pci/access.c > @@ -289,11 +289,10 @@ void pci_cfg_access_lock(struct pci_dev *dev) > { > might_sleep(); > > - lock_map_acquire(&dev->cfg_access_lock); > - > raw_spin_lock_irq(&pci_lock); > if (dev->block_cfg_access) > pci_wait_cfg(dev); > + lock_map_acquire(&dev->cfg_access_lock); > dev->block_cfg_access = 1; > raw_spin_unlock_irq(&pci_lock); > } > @@ -315,8 +314,10 @@ bool pci_cfg_access_trylock(struct pci_dev *dev) > raw_spin_lock_irqsave(&pci_lock, flags); > if (dev->block_cfg_access) > locked = false; > - else > + else { > + lock_map_acquire(&dev->cfg_access_lock); > dev->block_cfg_access = 1; > + } > raw_spin_unlock_irqrestore(&pci_lock, flags); > > return locked; > @@ -342,11 +343,10 @@ void pci_cfg_access_unlock(struct pci_dev *dev) > WARN_ON(!dev->block_cfg_access); > > dev->block_cfg_access = 0; > + lock_map_release(&dev->cfg_access_lock); > raw_spin_unlock_irqrestore(&pci_lock, flags); > > wake_up_all(&pci_cfg_wait); > - > - lock_map_release(&dev->cfg_access_lock); > } > EXPORT_SYMBOL_GPL(pci_cfg_access_unlock); > >