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Date: Thu, 15 Jan 2009 19:15:04 +0900
From: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
CC: "Rafael J. Wysocki" <rjw@...k.pl>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI PCIe portdrv: Fix allocation of interrupts (rev.
3)
Hidetoshi Seto wrote:
> 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.
>
Maybe I should have said:
The patch will not work if any of PME/HP or AER requires entry
other than first two.
> 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).
>
Yes. My opinion is MSI-X should work even if PME/HP or AER requires
entry other than first two.
> 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.
>
This is exactly my worry, and it's why I want to eliminate the
assumptions above.
Thanks,
Kenji Kaneshige
> Thanks,
> H.Seto
>
>>> Thanks,
>>> Rafael
>>>
>>> ---
>>> Subject: PCI PCIe portdrv: Fix allocation of interrupts (rev. 3)
>>> From: Rafael J. Wysocki <rjw@...k.pl>
>>>
>>> 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@...k.pl>
>>> ---
>>> 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, ®16);
>>> + 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, ®32);
>>> + 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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