linux-kernel - [PATCH 2/2] PCI: Cache offset of Resizable BAR capability

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20250208050329.1092214-3-helgaas@kernel.org>
Date: Fri,  7 Feb 2025 23:03:29 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Alex Williamson <alex.williamson@...hat.com>,
	Christian König <ckoenig.leichtzumerken@...il.com>
Cc: linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH 2/2] PCI: Cache offset of Resizable BAR capability

From: Bjorn Helgaas <bhelgaas@...gle.com>

Previously most resizable BAR interfaces (pci_rebar_get_possible_sizes(),
pci_rebar_set_size(), etc) as well as pci_restore_state() searched config
space for a Resizable BAR capability.  Most devices don't have such a
capability, so this is wasted effort, especially for pci_restore_state().

Search for a Resizable BAR capability once at enumeration-time and cache
the offset so we don't have to search every time we need it.  No functional
change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/pci.c   | 9 +++++++--
 drivers/pci/pci.h   | 1 +
 drivers/pci/probe.c | 1 +
 include/linux/pci.h | 1 +
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 503376bf7e75..cf2632080a94 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1872,7 +1872,7 @@ static void pci_restore_rebar_state(struct pci_dev *pdev)
 	unsigned int pos, nbars, i;
 	u32 ctrl;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
+	pos = pdev->rebar_cap;
 	if (!pos)
 		return;
 
@@ -3719,6 +3719,11 @@ void pci_acs_init(struct pci_dev *dev)
 	pci_enable_acs(dev);
 }
 
+void pci_rebar_init(struct pci_dev *pdev)
+{
+	pdev->rebar_cap = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
+}
+
 /**
  * pci_rebar_find_pos - find position of resize ctrl reg for BAR
  * @pdev: PCI device
@@ -3733,7 +3738,7 @@ static int pci_rebar_find_pos(struct pci_dev *pdev, int bar)
 	unsigned int pos, nbars, i;
 	u32 ctrl;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
+	pos = pdev->rebar_cap;
 	if (!pos)
 		return -ENOTSUPP;
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 01e51db8d285..d7b46ddfd6d2 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -799,6 +799,7 @@ static inline int acpi_get_rc_resources(struct device *dev, const char *hid,
 }
 #endif
 
+void pci_rebar_init(struct pci_dev *pdev);
 int pci_rebar_get_current_size(struct pci_dev *pdev, int bar);
 int pci_rebar_set_size(struct pci_dev *pdev, int bar, int size);
 static inline u64 pci_rebar_size_to_bytes(int size)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b6536ed599c3..24dd3dcfd223 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2564,6 +2564,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	pci_rcec_init(dev);		/* Root Complex Event Collector */
 	pci_doe_init(dev);		/* Data Object Exchange */
 	pci_tph_init(dev);		/* TLP Processing Hints */
+	pci_rebar_init(dev);		/* Resizable BAR */
 
 	pcie_report_downtraining(dev);
 	pci_init_reset_methods(dev);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 47b31ad724fa..9e5bbd996c83 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -353,6 +353,7 @@ struct pci_dev {
 	struct pci_dev  *rcec;          /* Associated RCEC device */
 #endif
 	u32		devcap;		/* PCIe Device Capabilities */
+	u16		rebar_cap;	/* Resizable BAR capability offset */
 	u8		pcie_cap;	/* PCIe capability offset */
 	u8		msi_cap;	/* MSI capability offset */
 	u8		msix_cap;	/* MSI-X capability offset */
-- 
2.34.1