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    SubjectRe: BUG in drivers/dma/ioat/dma_v2.c:314
    [ adding Matthew as one of last people to touch mm/dmapool.c ]

    On Tue, 2010-07-06 at 16:40 -0700, Chris Li wrote:
    > On Mon, Jul 5, 2010 at 3:16 AM, David Woodhouse <> wrote:
    > > On Fri, 2010-07-02 at 20:00 +0100, Chris Li wrote:
    > >> But I don't see the line that print out BIOS is lying.
    > >
    > > Hrm. Want to augment the dmar_find_matched_drhd_unit() function to
    > > _always_ print the DRHD returned for the offending PCI device? And if
    > > that still doesn't show, make it print pdev->vendor, pdev->device and
    > > the returned DRHD pointer for _every_ call?
    > I just did some experiment, my PCI device ID is PCI_DEVICE_ID_INTEL_ESB2_0
    > (0x2670) instead of PCI_DEVICE_ID_INTEL_IOAT_SNB.

    No, it should be PCI_DEVICE_ID_INTEL_IOAT_SNB (0x402f) for the dma
    engine at 00:0f.0 . PCI_DEVICE_ID_INTEL_ESB2_0 is the LPC controller at

    > That seems to be the reason preventing the warning to be print out. I am not
    > sure the warning should be always print out. Just curious why it did
    > not trigger.

    It should always trigger, and I have verified as much with the attached
    replacement patch (by forcing the error on a working system), but we run
    into a new problem. dma_pool_alloc() assumes that any dma_mapping error
    is transient. Do we need a new type of dma_mapping_error() that
    indicates permanent failure versus ENOMEM? The driver can handle the
    allocation failure, but it never gets the chance.

    ------------[ cut here ]------------
    WARNING: at drivers/pci/dmar.c:574 dmar_find_matched_drhd_unit+0xe4/0xfa()
    Hardware name: [redacted to protect the innocent]
    BIOS wrongly assigned I/OAT IOMMU 5: reg_base_addr fe71a000 cap 4900800c2f0462 ecap e01
    Modules linked in: ioatdma(+) dca ipv6 snd_pcsp snd_pcm snd_timer snd soundcore i2c_i801 snd_page_alloc serio_raw i2c_core joydev
    Pid: 1166, comm: modprobe Not tainted 2.6.35-rc3+ #2
    Call Trace:
    [<ffffffff8104bfd0>] warn_slowpath_common+0x85/0x9d
    [<ffffffff8104c043>] warn_slowpath_fmt_taint+0x3f/0x41
    [<ffffffff8125dd4b>] dmar_find_matched_drhd_unit+0xe4/0xfa
    [<ffffffff8126179d>] get_domain_for_dev.clone.3+0x111/0x471
    [<ffffffff81261cbb>] get_valid_domain_for_dev+0x26/0x9a
    [<ffffffff81261f51>] __intel_map_single+0x4c/0x175
    [<ffffffff81262184>] intel_alloc_coherent+0xc7/0xef
    [<ffffffff810edcd2>] dma_pool_alloc+0x179/0x2ab
    [<ffffffffa00ed606>] ? kzalloc+0x14/0x16 [ioatdma]
    [<ffffffffa00efe58>] ioat2_alloc_chan_resources+0x4f/0x219 [ioatdma]
    [<ffffffffa00f33b9>] ioat_dma_self_test+0x94/0x2af [ioatdma]
    [<ffffffff8109bff2>] ? devm_request_threaded_irq+0x98/0xaa
    [<ffffffffa00f31cd>] ioat_probe+0x338/0x3aa [ioatdma]
    [<ffffffffa00f3657>] ioat2_dma_probe+0x83/0x106 [ioatdma]
    [<ffffffffa00f2ded>] ioat_pci_probe+0x133/0x195 [ioatdma]
    [<ffffffff8124b539>] local_pci_probe+0x17/0x1b
    [<ffffffff8124c2f5>] pci_device_probe+0xcd/0xfd
    [<ffffffff812ee5f5>] ? driver_sysfs_add+0x4c/0x71
    [<ffffffff812ee81a>] driver_probe_device+0x12f/0x240
    [<ffffffff812ee97a>] __driver_attach+0x4f/0x6b
    [<ffffffff812ee92b>] ? __driver_attach+0x0/0x6b
    [<ffffffff812edc66>] bus_for_each_dev+0x53/0x88
    [<ffffffff812ee554>] driver_attach+0x1e/0x20
    [<ffffffff812ee19a>] bus_add_driver+0xd5/0x23b
    [<ffffffff812eec54>] driver_register+0x9d/0x10e
    [<ffffffff8124c521>] __pci_register_driver+0x58/0xc8
    [<ffffffffa00fc000>] ? ioat_init_module+0x0/0x85 [ioatdma]
    [<ffffffffa00fc000>] ? ioat_init_module+0x0/0x85 [ioatdma]
    [<ffffffffa00fc06d>] ioat_init_module+0x6d/0x85 [ioatdma]
    [<ffffffff81002069>] do_one_initcall+0x5e/0x159
    [<ffffffff8107bd01>] sys_init_module+0xa1/0x1e0
    [<ffffffff81009c32>] system_call_fastpath+0x16/0x1b
    ---[ end trace 02c1ac1f56dc9544 ]---
    Disabling lock debugging due to kernel taint
    IOMMU: can't find DMAR for device 0000:00:0f.0
    Allocating domain for 0000:00:0f.0 failed
    IOMMU: can't find DMAR for device 0000:00:0f.0
    Allocating domain for 0000:00:0f.0 failed
    [ infinitum...]


    diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
    index 0a19708..f183ac9 100644
    --- a/drivers/pci/dmar.c
    +++ b/drivers/pci/dmar.c
    @@ -532,7 +532,7 @@ static int dmar_pci_device_match(struct pci_dev *devices[], int cnt,
    struct dmar_drhd_unit *
    dmar_find_matched_drhd_unit(struct pci_dev *dev)
    - struct dmar_drhd_unit *dmaru = NULL;
    + struct dmar_drhd_unit *dmaru, *found = NULL;
    struct acpi_dmar_hardware_unit *drhd;

    dev = pci_physfn(dev);
    @@ -544,14 +544,38 @@ dmar_find_matched_drhd_unit(struct pci_dev *dev)

    if (dmaru->include_all &&
    drhd->segment == pci_domain_nr(dev->bus))
    - return dmaru;
    - if (dmar_pci_device_match(dmaru->devices,
    + found = dmaru;
    + else if (dmar_pci_device_match(dmaru->devices,
    dmaru->devices_cnt, dev))
    - return dmaru;
    + found = dmaru;
    + if (found)
    + break;
    + }
    + /* We know that this device only exists on this chipset, has its
    + * own IOMMU, and is uniquely identified by bit 54 being set in
    + * its capability mask. Catch BIOSes that specify the incorrect
    + * IOMMU unit.
    + */
    + if (found &&
    + dev->vendor == PCI_VENDOR_ID_INTEL &&
    + dev->device == PCI_DEVICE_ID_INTEL_IOAT_SNB &&
    + !test_bit(54, (unsigned long *) &found->iommu->cap)) {
    + struct intel_iommu *iommu = found->iommu;
    + "BIOS wrongly assigned I/OAT IOMMU "
    + "%d: reg_base_addr %llx cap %llx ecap %llx\n",
    + iommu->seq_id,
    + (unsigned long long)found->reg_base_addr,
    + (unsigned long long)iommu->cap,
    + (unsigned long long)iommu->ecap);
    + found = NULL;

    - return NULL;
    + return found;

    int __init dmar_dev_scope_init(void)
     \ /
      Last update: 2010-07-07 02:43    [W:0.025 / U:6.380 seconds]
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