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[210.128.90.14]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-219dca01965sm1376775ad.240.2024.12.18.16.53.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Dec 2024 16:53:42 -0800 (PST) From: Ryo Takakura To: lgoncalv@redhat.com, bigeasy@linutronix.de, kbusch@kernel.org Cc: bhelgaas@google.com, jonathan.derrick@linux.dev, kw@linux.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-rt-devel@lists.linux.dev, lpieralisi@kernel.org, manivannan.sadhasivam@linaro.org, nirmal.patel@linux.intel.com, robh@kernel.org, rostedt@goodmis.org Subject: Re: [PATCH v2] PCI: vmd: Fix spinlock usage on config access for RT kernel Date: Thu, 19 Dec 2024 09:53:36 +0900 Message-Id: <20241219005336.8603-1-ryotkkr98@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi all! on Wed, 18 Dec 2024 13:35:07 -0300, Luis Claudio R. Goncalves wrote: >On Wed, Dec 18, 2024 at 08:57:53AM -0700, Keith Busch wrote: >> On Wed, Dec 18, 2024 at 04:48:38PM +0100, Sebastian Andrzej Siewior wrote: >> > On 2024-12-18 08:36:54 [-0700], Keith Busch wrote: >> > > On Wed, Dec 18, 2024 at 08:59:51PM +0900, Ryo Takakura wrote: >> > > > PCI config access is locked with pci_lock which serializes >> > > > pci_user/bus_write_config*() and pci_user/bus_read_config*(). >> > > > The subsequently invoked vmd_pci_write() and vmd_pci_read() are also >> > > > serialized as they are only invoked by them respectively. >> > > > >> > > > Remove cfg_lock which is taken by vmd_pci_write() and vmd_pci_read() >> > > > for their serialization as its already serialized by pci_lock. >> > > >> > > That's only true if CONFIG_PCI_LOCKLESS_CONFIG isn't set, so pci_lock >> > > won't help with concurrent kernel config access in such a setup. I think >> > > the previous change to raw lock proposal was the correct approach. >> > >> > I overlooked that. Wouldn't it make sense to let the vmd driver select >> > that option rather than adding/ having a lock for the same purpose? >> >> The arch/x86/Kconfig always selects PCI_LOCKESS_CONFIG, so I don't think >> the vmd driver can require it be turned off. Besides, no need to punish >> all PCI access if only this device requires it be serialized. > >Sorry, I also missed that and induced Ryo Takakura to rewrite the patch. My apologies I missed that as well. I'll send the first version of the patch once again! >Luis Sincerely, Ryo Takakura