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    Subject[017/129] PCI: MSI: Remove unsafe and unnecessary hardware access
    2.6.35-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Ben Hutchings <bhutchings@solarflare.com>

    commit fcd097f31a6ee207cc0c3da9cccd2a86d4334785 upstream.

    During suspend on an SMP system, {read,write}_msi_msg_desc() may be
    called to mask and unmask interrupts on a device that is already in a
    reduced power state. At this point memory-mapped registers including
    MSI-X tables are not accessible, and config space may not be fully
    functional either.

    While a device is in a reduced power state its interrupts are
    effectively masked and its MSI(-X) state will be restored when it is
    brought back to D0. Therefore these functions can simply read and
    write msi_desc::msg for devices not in D0.

    Further, read_msi_msg_desc() should only ever be used to update a
    previously written message, so it can always read msi_desc::msg
    and never needs to touch the hardware.

    Tested-by: "Michael Chan" <mchan@broadcom.com>
    Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
    Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/pci/msi.c | 36 ++++++++++++------------------------
    1 file changed, 12 insertions(+), 24 deletions(-)

    --- a/drivers/pci/msi.c
    +++ b/drivers/pci/msi.c
    @@ -196,30 +196,15 @@ void unmask_msi_irq(unsigned int irq)
    void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
    {
    struct msi_desc *entry = get_irq_desc_msi(desc);
    - if (entry->msi_attrib.is_msix) {
    - void __iomem *base = entry->mask_base +
    - entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;

    - msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
    - msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
    - msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
    - } else {
    - struct pci_dev *dev = entry->dev;
    - int pos = entry->msi_attrib.pos;
    - u16 data;
    -
    - pci_read_config_dword(dev, msi_lower_address_reg(pos),
    - &msg->address_lo);
    - if (entry->msi_attrib.is_64) {
    - pci_read_config_dword(dev, msi_upper_address_reg(pos),
    - &msg->address_hi);
    - pci_read_config_word(dev, msi_data_reg(pos, 1), &data);
    - } else {
    - msg->address_hi = 0;
    - pci_read_config_word(dev, msi_data_reg(pos, 0), &data);
    - }
    - msg->data = data;
    - }
    + /* We do not touch the hardware (which may not even be
    + * accessible at the moment) but return the last message
    + * written. Assert that this is valid, assuming that
    + * valid messages are not all-zeroes. */
    + BUG_ON(!(entry->msg.address_hi | entry->msg.address_lo |
    + entry->msg.data));
    +
    + *msg = entry->msg;
    }

    void read_msi_msg(unsigned int irq, struct msi_msg *msg)
    @@ -232,7 +217,10 @@ void read_msi_msg(unsigned int irq, stru
    void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
    {
    struct msi_desc *entry = get_irq_desc_msi(desc);
    - if (entry->msi_attrib.is_msix) {
    +
    + if (entry->dev->current_state != PCI_D0) {
    + /* Don't touch the hardware now */
    + } else if (entry->msi_attrib.is_msix) {
    void __iomem *base;
    base = entry->mask_base +
    entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;



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