Currently pci_enable_msi_block() and pci_enable_msix() interfaces return a error code in case of failure, 0 in case of success and a positive value which indicates the number of MSI-X/MSI interrupts that could have been allocated. The latter value should be passed to a repeated call to the interfaces until a failure or success. This technique proved to be confusing and error-prone. Vast share of device drivers simply fail to follow the described guidelines. This update converts pci_enable_msix() and pci_enable_msi_block() interfaces to canonical kernel functions and makes them return a error code in case of failure or 0 in case of success. As result, device drivers will cease to use the overcomplicated repeated fallbacks technique and resort to a straightforward pattern - determine the number of MSI/MSI-X interrupts required before calling pci_enable_msix() and pci_enable_msi_block() interfaces. Device drivers will use their knowledge of underlying hardware to determine the number of MSI/MSI-X interrupts required. The simplest case would be requesting all available interrupts - to obtain that value device drivers will use pci_get_msi_cap() interface for MSI and pci_msix_table_size() for MSI-X. More complex cases would entail matching device capabilities with the system environment, i.e. limiting number of hardware queues (and hence associated MSI/MSI-X interrupts) to the number of online CPUs. Suggested-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx> --- Documentation/PCI/MSI-HOWTO.txt | 71 ++++++++++++++++++--------------- arch/mips/pci/msi-octeon.c | 2 +- arch/powerpc/kernel/msi.c | 2 +- arch/powerpc/platforms/pseries/msi.c | 2 +- arch/s390/pci/pci.c | 2 +- arch/x86/kernel/apic/io_apic.c | 2 +- drivers/pci/msi.c | 52 +++++++------------------ 7 files changed, 58 insertions(+), 75 deletions(-) diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index 1f37ce2..40abcfb 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -111,21 +111,27 @@ the device are in the range dev->irq to dev->irq + count - 1. If this function returns a negative number, it indicates an error and the driver should not attempt to request any more MSI interrupts for -this device. If this function returns a positive number, it is -less than 'count' and indicates the number of interrupts that could have -been allocated. In neither case is the irq value updated or the device -switched into MSI mode. - -The device driver must decide what action to take if -pci_enable_msi_block() returns a value less than the number requested. -For instance, the driver could still make use of fewer interrupts; -in this case the driver should call pci_enable_msi_block() -again. Note that it is not guaranteed to succeed, even when the -'count' has been reduced to the value returned from a previous call to -pci_enable_msi_block(). This is because there are multiple constraints -on the number of vectors that can be allocated; pci_enable_msi_block() -returns as soon as it finds any constraint that doesn't allow the -call to succeed. +this device. + +Device drivers should normally call pci_get_msi_cap() function before +calling this function to determine maximum number of MSI interrupts +a device can send. + +A sequence to achieve that might look like: + +static int foo_driver_enable_msi(struct foo_adapter *adapter, int nvec) +{ + rc = pci_get_msi_cap(adapter->pdev); + if (rc < 0) + return rc; + + nvec = min(nvec, rc); + if (nvec < FOO_DRIVER_MINIMUM_NVEC) { + return -ENOSPC; + + rc = pci_enable_msi_block(adapter->pdev, nvec); + return rc; +} 4.2.3 pci_enable_msi_block_auto @@ -218,9 +224,7 @@ interrupts assigned to the MSI-X vectors so it can free them again later. If this function returns a negative number, it indicates an error and the driver should not attempt to allocate any more MSI-X interrupts for -this device. If it returns a positive number, it indicates the maximum -number of interrupt vectors that could have been allocated. See example -below. +this device. This function, in contrast with pci_enable_msi(), does not adjust dev->irq. The device will not generate interrupts for this interrupt @@ -229,24 +233,27 @@ number once MSI-X is enabled. Device drivers should normally call this function once per device during the initialization phase. -It is ideal if drivers can cope with a variable number of MSI-X interrupts; -there are many reasons why the platform may not be able to provide the -exact number that a driver asks for. +Device drivers should normally call pci_msix_table_size() function before +calling this function to determine maximum number of MSI-X interrupts +a device can send. -A request loop to achieve that might look like: +A sequence to achieve that might look like: static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec) { - while (nvec >= FOO_DRIVER_MINIMUM_NVEC) { - rc = pci_enable_msix(adapter->pdev, - adapter->msix_entries, nvec); - if (rc > 0) - nvec = rc; - else - return rc; - } - - return -ENOSPC; + rc = pci_msix_table_size(adapter->pdev); + if (rc < 0) + return rc; + + nvec = min(nvec, rc); + if (nvec < FOO_DRIVER_MINIMUM_NVEC) { + return -ENOSPC; + + for (i = 0; i < nvec; i++) + adapter->msix_entries[i].entry = i; + + rc = pci_enable_msix(adapter->pdev, adapter->msix_entries, nvec); + return rc; } 4.3.2 pci_disable_msix diff --git a/arch/mips/pci/msi-octeon.c b/arch/mips/pci/msi-octeon.c index d37be36..0ee5f4d 100644 --- a/arch/mips/pci/msi-octeon.c +++ b/arch/mips/pci/msi-octeon.c @@ -193,7 +193,7 @@ int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) * override arch_setup_msi_irqs() */ if (type == PCI_CAP_ID_MSI && nvec > 1) - return 1; + return -EINVAL; list_for_each_entry(entry, &dev->msi_list, list) { ret = arch_setup_msi_irq(dev, entry); diff --git a/arch/powerpc/kernel/msi.c b/arch/powerpc/kernel/msi.c index 8bbc12d..36d70b9 100644 --- a/arch/powerpc/kernel/msi.c +++ b/arch/powerpc/kernel/msi.c @@ -22,7 +22,7 @@ int arch_msi_check_device(struct pci_dev* dev, int nvec, int type) /* PowerPC doesn't support multiple MSI yet */ if (type == PCI_CAP_ID_MSI && nvec > 1) - return 1; + return -EINVAL; if (ppc_md.msi_check_device) { pr_debug("msi: Using platform check routine.\n"); diff --git a/arch/powerpc/platforms/pseries/msi.c b/arch/powerpc/platforms/pseries/msi.c index 009ec73..89648c1 100644 --- a/arch/powerpc/platforms/pseries/msi.c +++ b/arch/powerpc/platforms/pseries/msi.c @@ -348,7 +348,7 @@ static int rtas_msi_check_device(struct pci_dev *pdev, int nvec, int type) quota = msi_quota_for_device(pdev, nvec); if (quota && quota < nvec) - return quota; + return -ENOSPC; return 0; } diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index 61a3c2c..45a1875 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -426,7 +426,7 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type) pr_debug("%s: requesting %d MSI-X interrupts...", __func__, nvec); if (type == PCI_CAP_ID_MSI && nvec > 1) - return 1; + return -EINVAL; msi_vecs = min(nvec, ZPCI_MSI_VEC_MAX); msi_vecs = min_t(unsigned int, msi_vecs, CONFIG_PCI_NR_MSI); diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index e63a5bd..6126eaf 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -3145,7 +3145,7 @@ int native_setup_msi_irqs(struct pci_dev *dev, int nvec, int type) /* Multiple MSI vectors only supported with interrupt remapping */ if (type == PCI_CAP_ID_MSI && nvec > 1) - return 1; + return -EINVAL; node = dev_to_node(&dev->dev); irq_want = nr_irqs_gsi; diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index ca59bfc..583ace1 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -719,7 +719,7 @@ static int msix_capability_init(struct pci_dev *dev, ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX); if (ret) - goto out_avail; + goto error; /* * Some devices require MSI-X to be enabled before we can touch the @@ -733,7 +733,7 @@ static int msix_capability_init(struct pci_dev *dev, ret = populate_msi_sysfs(dev); if (ret) - goto out_free; + goto error; /* Set MSI-X enabled bits and unmask the function */ pci_intx_for_msi(dev, 0); @@ -744,24 +744,7 @@ static int msix_capability_init(struct pci_dev *dev, return 0; -out_avail: - if (ret < 0) { - /* - * If we had some success, report the number of irqs - * we succeeded in setting up. - */ - struct msi_desc *entry; - int avail = 0; - - list_for_each_entry(entry, &dev->msi_list, list) { - if (entry->irq != 0) - avail++; - } - if (avail != 0) - ret = avail; - } - -out_free: +error: free_msi_irqs(dev); return ret; @@ -832,13 +815,11 @@ EXPORT_SYMBOL(pci_get_msi_cap); * @dev: device to configure * @nvec: number of interrupts to configure * - * Allocate IRQs for a device with the MSI capability. - * This function returns a negative errno if an error occurs. If it - * is unable to allocate the number of interrupts requested, it returns - * the number of interrupts it might be able to allocate. If it successfully - * allocates at least the number of interrupts requested, it returns 0 and - * updates the @dev's irq member to the lowest new interrupt number; the - * other interrupt numbers allocated to this device are consecutive. + * Allocate IRQs for a device with the MSI capability. This function returns + * a negative errno if an error occurs. If it successfully allocates at least + * the number of interrupts requested, it returns 0 and updates the @dev's + * irq member to the lowest new interrupt number; the other interrupt numbers + * allocated to this device are consecutive. */ int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec) { @@ -848,7 +829,7 @@ int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec) if (maxvec < 0) return maxvec; if (nvec > maxvec) - return maxvec; + return -EINVAL; status = pci_msi_check_device(dev, nvec, PCI_CAP_ID_MSI); if (status) @@ -879,13 +860,11 @@ int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec) if (maxvec) *maxvec = ret; - do { - nvec = ret; - ret = pci_enable_msi_block(dev, nvec); - } while (ret > 0); - - if (ret < 0) + nvec = ret; + ret = pci_enable_msi_block(dev, nvec); + if (ret) return ret; + return nvec; } EXPORT_SYMBOL(pci_enable_msi_block_auto); @@ -955,9 +934,6 @@ EXPORT_SYMBOL(pci_msix_table_size); * MSI-X mode enabled on its hardware device function. A return of zero * indicates the successful configuration of MSI-X capability structure * with new allocated MSI-X irqs. A return of < 0 indicates a failure. - * Or a return of > 0 indicates that driver request is exceeding the number - * of irqs or MSI-X vectors available. Driver should use the returned value to - * re-send its request. **/ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec) { @@ -975,7 +951,7 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec) if (nr_entries < 0) return nr_entries; if (nvec > nr_entries) - return nr_entries; + return -EINVAL; /* Check for any invalid entries */ for (i = 0; i < nvec; i++) { -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html