Re: [PATCH] PCI PCIe portdrv: Fix allocation of interrupts (rev.3)

From: Hidetoshi Seto
Date: Thu Jan 15 2009 - 02:53:23 EST

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In reply to: Kenji Kaneshige: "Re: [PATCH] PCI PCIe portdrv: Fix allocation of interrupts (rev.3)"
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Kenji Kaneshige wrote:
> Rafael J. Wysocki wrote:
>> Hi,
>>
>> The patch below fixes the problem with MSI-X vectors allocation by the PCIe
>> port driver. It applies on top of the series of PCIe port driver cleanups and
>> bug fixes I've just sent.
>>
>> Please review.
>>
>
> The patch seems to still have the following assumptions.
>
> - The number of MSI-X table entries is less than or equal to two.
> - MSI-X table entries are mapped only to PME/HP and/or AER.

It is not true.

If any of PME/HP and AER requires entry other than first two ([0],[1]),
this code will give up MSI-X and fall back to MSI (or INTx).

In other words, the portdrv will use MSI-X only if entries for PME/PM
and AER is in the first two entries of the MSI-X table.

Thanks,
H.Seto

>> Thanks,
>> Rafael
>>
>> ---
>> Subject: PCI PCIe portdrv: Fix allocation of interrupts (rev. 3)
>> From: Rafael J. Wysocki <rjw@xxxxxxx>
>>
>> If MSI-X interrupt mode is used by the PCI Express port driver, too
>> many vectors are allocated and it is not ensured that the right
>> vectors will be used for the right services. Namely, the PCI Express
>> specification states that both PCI Express native PME and PCI Express
>> hotplug will always use the same MSI or MSI-X message for signalling
>> interrupts, which implies that the same vector will be used by both
>> of them. Also, the VC service does not use interrupts at all.
>> Moreover, is not clear which of the vectors allocated by
>> pci_enable_msix() will be used for PME and hotplug and which of them
>> will be used for AER if all of these services are configured.
>>
>> For these reasons, rework the allocation of interrupts for PCI
>> Express ports so that at most two vectors are allocated and ensure
>> that the right vector will be used for the right purpose.
>>
>> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
>> ---
>> drivers/pci/pcie/portdrv.h | 2
>> drivers/pci/pcie/portdrv_core.c | 142 +++++++++++++++++++++++++++++-----------
>> include/linux/pcieport_if.h | 12 ++-
>> 3 files changed, 114 insertions(+), 42 deletions(-)
>>
>> Index: linux-2.6/drivers/pci/pcie/portdrv_core.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/pci/pcie/portdrv_core.c
>> +++ linux-2.6/drivers/pci/pcie/portdrv_core.c
>> @@ -31,6 +31,72 @@ static void release_pcie_device(struct d
>> }
>>
>> /**
>> + * pcie_port_enable_msix - try to set up MSI-X as interrupt mode for given port
>> + * @dev: PCI Express port to handle
>> + * @vectors: Array of interrupt vectors to populate
>> + * @nvec: Number of interrupt vectors to allocate
>> + *
>> + * Return value: 0 on success, error code on failure
>> + */
>> +static int pcie_port_enable_msix(struct pci_dev *dev, int *vectors, int nvec)
>> +{
>> + struct msix_entry msix_entries[PCIE_PORT_DEVICE_MAXINTERRUPTS] = {
>> + { 0, },
>> + };
>> + int status, pos, i;
>> + u16 reg16;
>> + u32 reg32;
>> +
>> + for (i = 0; i < nvec; i++)
>> + msix_entries[i].entry = i;
>> +
>> + status = pci_enable_msix(dev, msix_entries, nvec);
>> + if (status)
>> + return status;
>> +
>> + /*
>> + * The code below follows the PCI Express Base Specification 2.0 clearly
>> + * stating in Section 6.1.6 that "PME and Hot-Plug Event interrupts
>> + * (when both are implemented) always share the same MSI or MSI-X
>> + * vector, as indicated by the Interrupt Message Number field in the PCI
>> + * Express Capabilities register", where according to Section 7.8.2 of
>> + * the Specification "For MSI-X, the value in this field indicates which
>> + * MSI-X Table entry is used to generate the interrupt message."
>> + */
>> + pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
>> + pci_read_config_word(dev, pos + PCIE_CAPABILITIES_REG, &reg16);
>> + i = (reg16 >> 9) & PCIE_PORT_MSI_VECTOR_MASK;
>> + if (i >= nvec) {
>> + goto Error;
>> + } else {
>> + vectors[PCIE_PORT_SERVICE_PME_SHIFT] = msix_entries[i].vector;
>> + vectors[PCIE_PORT_SERVICE_HP_SHIFT] = msix_entries[i].vector;
>> + }
>> +
>> + /*
>> + * The code below follows Section 7.10.10 of the PCI Express Base
>> + * Specification 2.0 stating that bits 31-27 of the Root Error Status
>> + * Register contain a value indicating which of the MSI/MSI-X vectors
>> + * assigned to the port is going to be used for AER, where "For MSI-X,
>> + * the value in this register indicates which MSI-X Table entry is used
>> + * to generate the interrupt message."
>> + */
>> + pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
>> + pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &reg32);
>> + i = (reg32 >> 27) & PCIE_PORT_MSI_VECTOR_MASK;
>> + if (i >= nvec)
>> + goto Error;
>> + else
>> + vectors[PCIE_PORT_SERVICE_AER_SHIFT] = msix_entries[i].vector;
>> +
>> + return 0;
>> +
>> + Error:
>> + pci_disable_msix(dev);
>> + return -EIO;
>> +}
>> +
>> +/**
>> * assign_interrupt_mode - choose interrupt mode for PCI Express port services
>> * (INTx, MSI-X, MSI) and set up vectors
>> * @dev: PCI Express port to handle
>> @@ -42,49 +108,49 @@ static void release_pcie_device(struct d
>> static int assign_interrupt_mode(struct pci_dev *dev, int *vectors, int mask)
>> {
>> struct pcie_port_data *port_data = pci_get_drvdata(dev);
>> - int i, pos, nvec, status = -EINVAL;
>> - int interrupt_mode = PCIE_PORT_NO_IRQ;
>> + int nvec, irq, interrupt_mode = PCIE_PORT_NO_IRQ;
>> + int i;
>>
>> - /* Set INTx as default */
>> - for (i = 0, nvec = 0; i < PCIE_PORT_DEVICE_MAXSERVICES; i++) {
>> - if (mask & (1 << i))
>> - nvec++;
>> - vectors[i] = dev->irq;
>> - }
>> - if (dev->pin)
>> - interrupt_mode = PCIE_PORT_INTx_MODE;
>> + /*
>> + * Determine the number of vectors to allocate.
>> + *
>> + * According to the PCI Express specification both PME and PCI Express
>> + * hotplug always use the same interrupt vector, while AER can use
>> + * a different one.
>> + */
>> + nvec = 0;
>> + if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP))
>> + nvec++;
>> + if (mask & PCIE_PORT_SERVICE_AER)
>> + nvec++;
>> + if (!nvec)
>> + return PCIE_PORT_NO_IRQ;
>>
>> /* Check MSI quirk */
>> if (port_data->port_type == PCIE_RC_PORT && pcie_mch_quirk)
>> - return interrupt_mode;
>> + goto Fallback;
>> +
>> + /* For nvec > 1 use MSI-X if supported */
>> + if (nvec > 1 && !pcie_port_enable_msix(dev, vectors, nvec)) {
>> + interrupt_mode = PCIE_PORT_MSIX_MODE;
>> + goto Exit;
>> + }
>> +
>> + /* We're not going to use MSI-X, so try MSI and fall back to INTx */
>> + if (!pci_enable_msi(dev))
>> + interrupt_mode = PCIE_PORT_MSI_MODE;
>> +
>> + Fallback:
>> + if (interrupt_mode == PCIE_PORT_NO_IRQ && dev->pin)
>> + interrupt_mode = PCIE_PORT_INTx_MODE;
>> +
>> + irq = interrupt_mode != PCIE_PORT_NO_IRQ ? dev->irq : -1;
>> + for (i = 0; i < PCIE_PORT_DEVICE_MAXSERVICES; i++)
>> + vectors[i] = irq;
>> +
>> + Exit:
>> + vectors[PCIE_PORT_SERVICE_VC_SHIFT] = -1;
>>
>> - /* Select MSI-X over MSI if supported */
>> - pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
>> - if (pos) {
>> - struct msix_entry msix_entries[PCIE_PORT_DEVICE_MAXSERVICES] =
>> - {{0, 0}, {0, 1}, {0, 2}, {0, 3}};
>> - status = pci_enable_msix(dev, msix_entries, nvec);
>> - if (!status) {
>> - int j = 0;
>> -
>> - interrupt_mode = PCIE_PORT_MSIX_MODE;
>> - for (i = 0; i < PCIE_PORT_DEVICE_MAXSERVICES; i++) {
>> - if (mask & (1 << i))
>> - vectors[i] = msix_entries[j++].vector;
>> - }
>> - }
>> - }
>> - if (status) {
>> - pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
>> - if (pos) {
>> - status = pci_enable_msi(dev);
>> - if (!status) {
>> - interrupt_mode = PCIE_PORT_MSI_MODE;
>> - for (i = 0;i < PCIE_PORT_DEVICE_MAXSERVICES;i++)
>> - vectors[i] = dev->irq;
>> - }
>> - }
>> - }
>> return interrupt_mode;
>> }
>>
>> Index: linux-2.6/include/linux/pcieport_if.h
>> ===================================================================
>> --- linux-2.6.orig/include/linux/pcieport_if.h
>> +++ linux-2.6/include/linux/pcieport_if.h
>> @@ -16,10 +16,14 @@
>> #define PCIE_ANY_PORT 7
>>
>> /* Service Type */
>> -#define PCIE_PORT_SERVICE_PME 1 /* Power Management Event */
>> -#define PCIE_PORT_SERVICE_AER 2 /* Advanced Error Reporting */
>> -#define PCIE_PORT_SERVICE_HP 4 /* Native Hotplug */
>> -#define PCIE_PORT_SERVICE_VC 8 /* Virtual Channel */
>> +#define PCIE_PORT_SERVICE_PME_SHIFT 0 /* Power Management Event */
>> +#define PCIE_PORT_SERVICE_PME (1 << PCIE_PORT_SERVICE_PME_SHIFT)
>> +#define PCIE_PORT_SERVICE_AER_SHIFT 1 /* Advanced Error Reporting */
>> +#define PCIE_PORT_SERVICE_AER (1 << PCIE_PORT_SERVICE_AER_SHIFT)
>> +#define PCIE_PORT_SERVICE_HP_SHIFT 2 /* Native Hotplug */
>> +#define PCIE_PORT_SERVICE_HP (1 << PCIE_PORT_SERVICE_HP_SHIFT)
>> +#define PCIE_PORT_SERVICE_VC_SHIFT 3 /* Virtual Channel */
>> +#define PCIE_PORT_SERVICE_VC (1 << PCIE_PORT_SERVICE_VC_SHIFT)
>>
>> /* Root/Upstream/Downstream Port's Interrupt Mode */
>> #define PCIE_PORT_NO_IRQ (-1)
>> Index: linux-2.6/drivers/pci/pcie/portdrv.h
>> ===================================================================
>> --- linux-2.6.orig/drivers/pci/pcie/portdrv.h
>> +++ linux-2.6/drivers/pci/pcie/portdrv.h
>> @@ -25,6 +25,8 @@
>> #define PCIE_CAPABILITIES_REG 0x2
>> #define PCIE_SLOT_CAPABILITIES_REG 0x14
>> #define PCIE_PORT_DEVICE_MAXSERVICES 4
>> +#define PCIE_PORT_DEVICE_MAXINTERRUPTS 2
>> +#define PCIE_PORT_MSI_VECTOR_MASK 0x1f
>>
>> #define get_descriptor_id(type, service) (((type - 4) << 4) | service)
>>
>>
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>
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Next message: Jarek Poplawski: "Re: deadlocks if use htb"
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In reply to: Kenji Kaneshige: "Re: [PATCH] PCI PCIe portdrv: Fix allocation of interrupts (rev.3)"
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