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    Subject[PATCH] msi: skip calling pci_find_capability from msi_set_mask_bits
    Jesse Barnes wrote:
    > Since we know MSI is a problem, let's just go with fixing that for now. If we
    > find that other caps are also causing problems we can revisit caching all of
    > them; the patch is simple enough.

    Humm...
    I suppose it can be more simple. How about this patch?


    > everytime handle_edge_irq is called it needs to mask and unmask MSI, and
    > that leads to a series of very expensive calls to pci_find_capability

    The position of MSI capability is already cached in the msi_desc when
    we enter the msi_set_mask_bits(). Use it instead.

    Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    ---
    drivers/pci/msi.c | 12 ++++++++----
    1 files changed, 8 insertions(+), 4 deletions(-)

    diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
    index 8c61304..ccb1974 100644
    --- a/drivers/pci/msi.c
    +++ b/drivers/pci/msi.c
    @@ -70,12 +70,10 @@ arch_teardown_msi_irqs(struct pci_dev *dev)
    }
    }

    -static void msi_set_enable(struct pci_dev *dev, int enable)
    +static void __msi_set_enable(struct pci_dev *dev, int pos, int enable)
    {
    - int pos;
    u16 control;

    - pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
    if (pos) {
    pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
    control &= ~PCI_MSI_FLAGS_ENABLE;
    @@ -85,6 +83,11 @@ static void msi_set_enable(struct pci_dev *dev, int enable)
    }
    }

    +static void msi_set_enable(struct pci_dev *dev, int enable)
    +{
    + __msi_set_enable(dev, pci_find_capability(dev, PCI_CAP_ID_MSI), enable);
    +}
    +
    static void msix_set_enable(struct pci_dev *dev, int enable)
    {
    int pos;
    @@ -141,7 +144,8 @@ static void msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
    mask_bits |= flag & mask;
    pci_write_config_dword(entry->dev, pos, mask_bits);
    } else {
    - msi_set_enable(entry->dev, !flag);
    + __msi_set_enable(entry->dev, entry->msi_attrib.pos,
    + !flag);
    }
    break;
    case PCI_CAP_ID_MSIX:
    --
    1.5.4.3


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