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    SubjectRe: [GIT PULL] AMD IOMMU updates for 2.6.28-rc5
    On Thu, Nov 20, 2008 at 01:25:15PM +0900, FUJITA Tomonori wrote:
    > On Wed, 19 Nov 2008 10:25:44 +0100
    > Joerg Roedel <> wrote:
    > > I found issues in network drivers only for now. The two drivers where I
    > > found issues are the in-kernel ixgbe driver (I see IO_PAGE_FAULTS
    > > there), the ixgbe version from the Intel website has a double-free bug
    > > when unloading the driver or changing the device mtu. The same problem
    > > was found with the Broadcom NetXtreme II driver.
    > I see, thanks. You already reported the bugs to netdev?

    Not yet, but I will do so when I can prove the bug is not in my driver
    ;) (== when my debug code is ready)

    > > We can't test all drivers for those bugs until 2.6.28 will be released.
    > > And these bugs can corrupt data, for example when a driver frees dma
    > > addresses allocated by another driver and these addresses are then
    > > reallocated.
    > > The only way to protect the drivers from each other is to isolate them
    > > in different protection domains. The AMD IOMMU driver prints a WARN_ON()
    > > if a driver frees dma addresses not yet mapped. This triggered with the
    > > bnx2 and the ixgbe driver.
    > It would be better to add such WARN_ON to VT-d. VT-d is everywhere
    > nowadays. I think that there are some developers who can test these
    > drivers with VT-d.

    Yes, I agree.

    > > And the data corruption is real, it eat the root-fs of my testbox one
    > > time.
    > > I agree that we need to fix the drivers. I plan to implement some debug
    > > code which allows driver developers to detect those bugs even if they
    > > have no IOMMU in the system.
    > It's not so hard to add such debug feature to swiotlb, I guess.

    Yes, but I prefer to have it outside of any dma_ops implementation. This
    way it can also be used to find out if a bug originated from the device
    driver or the dma_ops implementation.


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