Subject: [PATCH mlx5-next 1/4] PCI: Configure number of MSI-X vectors for SR-IOV VFs

From: Leon Romanovsky <[email-masked]>
Date: Sun, 3 Jan 2021 10:24:37 +0200

From: Leon Romanovsky <[email-masked]>

This function is applicable for SR-IOV VFs because such devices allocate
their MSI-X table before they will run on the targeted hardware and they
can't guess the right amount of vectors.

Signed-off-by: Leon Romanovsky <[email-masked]>
---
 Documentation/ABI/testing/sysfs-bus-pci | 16 +++++++
 drivers/pci/iov.c                       | 57 +++++++++++++++++++++++++
 drivers/pci/msi.c                       | 30 +++++++++++++
 drivers/pci/pci-sysfs.c                 |  1 +
 drivers/pci/pci.h                       |  1 +
 include/linux/pci.h                     |  8 ++++
 6 files changed, 113 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 25c9c39770c6..30720a9e1386 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -375,3 +375,19 @@ Description:
 		The value comes from the PCI kernel device state and can be one
 		of: "unknown", "error", "D0", D1", "D2", "D3hot", "D3cold".
 		The file is read only.
+
+What:		/sys/bus/pci/devices/.../vf_msix_vec
+Date:		December 2020
+Contact:	Leon Romanovsky <[email-masked]>
+Description:
+		This file is associated with the SR-IOV VFs. It allows overwrite
+		the amount of MSI-X vectors for that VF. This is needed to optimize
+		performance of newly bounded devices by allocating the number of
+		vectors based on the internal knowledge of targeted VM.
+
+		The values accepted are:
+		 * > 0 - this will be number reported by the PCI VF's PCIe MSI-X capability.
+		 * < 0 - not valid
+		 * = 0 - will reset to the device default value
+
+		The file is writable if no driver is bounded.
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 4afd4ee4f7f0..0f8c570361fc 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -31,6 +31,7 @@ int pci_iov_virtfn_devfn(struct pci_dev *dev, int vf_id)
 	return (dev->devfn + dev->sriov->offset +
 		dev->sriov->stride * vf_id) & 0xff;
 }
+EXPORT_SYMBOL(pci_iov_virtfn_devfn);

 /*
  * Per SR-IOV spec sec 3.3.10 and 3.3.11, First VF Offset and VF Stride may
@@ -426,6 +427,62 @@ const struct attribute_group sriov_dev_attr_group = {
 	.is_visible = sriov_attrs_are_visible,
 };

+#ifdef CONFIG_PCI_MSI
+static ssize_t vf_msix_vec_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int numb = pci_msix_vec_count(pdev);
+
+	if (numb < 0)
+		return numb;
+
+	return sprintf(buf, "%d\n", numb);
+}
+
+static ssize_t vf_msix_vec_store(struct device *dev,
+				 struct device_attribute *attr, const char *buf,
+				 size_t count)
+{
+	struct pci_dev *vf_dev = to_pci_dev(dev);
+	int val, ret;
+
+	ret = kstrtoint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	ret = pci_set_msix_vec_count(vf_dev, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_RW(vf_msix_vec);
+#endif
+
+static struct attribute *sriov_vf_dev_attrs[] = {
+#ifdef CONFIG_PCI_MSI
+	&dev_attr_vf_msix_vec.attr,
+#endif
+	NULL,
+};
+
+static umode_t sriov_vf_attrs_are_visible(struct kobject *kobj,
+					  struct attribute *a, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+
+	if (dev_is_pf(dev))
+		return 0;
+
+	return a->mode;
+}
+
+const struct attribute_group sriov_vf_dev_attr_group = {
+	.attrs = sriov_vf_dev_attrs,
+	.is_visible = sriov_vf_attrs_are_visible,
+};
+
 int __weak pcibios_sriov_enable(struct pci_dev *pdev, u16 num_vfs)
 {
 	return 0;
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 3162f88fe940..0bcd705487d9 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -991,6 +991,36 @@ int pci_msix_vec_count(struct pci_dev *dev)
 }
 EXPORT_SYMBOL(pci_msix_vec_count);

+/**
+ * pci_set_msix_vec_count - change the reported number of MSI-X vectors.
+ * This function is applicable for SR-IOV VFs because such devices allocate
+ * their MSI-X table before they will run on the targeted hardware and they
+ * can't guess the right amount of vectors.
+ * @dev: VF device that is going to be changed.
+ * @numb: amount of MSI-X vectors.
+ **/
+int pci_set_msix_vec_count(struct pci_dev *dev, int numb)
+{
+	struct pci_dev *pdev = pci_physfn(dev);
+
+	if (!dev->msix_cap || !pdev->msix_cap)
+		return -EINVAL;
+
+	if (dev->driver || !pdev->driver ||
+	    !pdev->driver->sriov_set_msix_vec_count)
+		return -EOPNOTSUPP;
+
+	if (numb < 0)
+		/*
+		 * We don't support negative numbers for now,
+		 * but maybe in the future it will make sense.
+		 */
+		return -EINVAL;
+
+	return pdev->driver->sriov_set_msix_vec_count(dev, numb);
+}
+EXPORT_SYMBOL(pci_set_msix_vec_count);
+
 static int __pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
 			     int nvec, struct irq_affinity *affd, int flags)
 {
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index fb072f4b3176..0af2222643c2 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1557,6 +1557,7 @@ static const struct attribute_group *pci_dev_attr_groups[] = {
 	&pci_dev_hp_attr_group,
 #ifdef CONFIG_PCI_IOV
 	&sriov_dev_attr_group,
+	&sriov_vf_dev_attr_group,
 #endif
 	&pci_bridge_attr_group,
 	&pcie_dev_attr_group,
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 5c59365092fa..46396a5da2d9 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -502,6 +502,7 @@ resource_size_t pci_sriov_resource_alignment(struct pci_dev *dev, int resno);
 void pci_restore_iov_state(struct pci_dev *dev);
 int pci_iov_bus_range(struct pci_bus *bus);
 extern const struct attribute_group sriov_dev_attr_group;
+extern const struct attribute_group sriov_vf_dev_attr_group;
 #else
 static inline int pci_iov_init(struct pci_dev *dev)
 {
diff --git a/include/linux/pci.h b/include/linux/pci.h
index b32126d26997..1acba40a1b1b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -856,6 +856,8 @@ struct module;
  *		e.g. drivers/net/e100.c.
  * @sriov_configure: Optional driver callback to allow configuration of
  *		number of VFs to enable via sysfs "sriov_numvfs" file.
+ * @sriov_set_msix_vec_count: Driver callback to change number of MSI-X vectors
+ *              exposed by the sysfs "vf_msix_vec" entry.
  * @err_handler: See Documentation/PCI/pci-error-recovery.rst
  * @groups:	Sysfs attribute groups.
  * @driver:	Driver model structure.
@@ -871,6 +873,7 @@ struct pci_driver {
 	int  (*resume)(struct pci_dev *dev);	/* Device woken up */
 	void (*shutdown)(struct pci_dev *dev);
 	int  (*sriov_configure)(struct pci_dev *dev, int num_vfs); /* On PF */
+	int  (*sriov_set_msix_vec_count)(struct pci_dev *vf, int msix_vec_count); /* On PF */
 	const struct pci_error_handlers *err_handler;
 	const struct attribute_group **groups;
 	struct device_driver	driver;
@@ -1464,6 +1467,7 @@ struct msix_entry {
 int pci_msi_vec_count(struct pci_dev *dev);
 void pci_disable_msi(struct pci_dev *dev);
 int pci_msix_vec_count(struct pci_dev *dev);
+int pci_set_msix_vec_count(struct pci_dev *dev, int numb);
 void pci_disable_msix(struct pci_dev *dev);
 void pci_restore_msi_state(struct pci_dev *dev);
 int pci_msi_enabled(void);
@@ -2402,6 +2406,10 @@ static inline bool pci_is_thunderbolt_attached(struct pci_dev *pdev)
 void pci_uevent_ers(struct pci_dev *pdev, enum  pci_ers_result err_type);
 #endif

+#ifdef CONFIG_PCI_IOV
+int pci_iov_virtfn_devfn(struct pci_dev *dev, int vf_id);
+#endif
+
 /* Provide the legacy pci_dma_* API */
 #include <linux/pci-dma-compat.h>

--
2.29.2