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    Subject[PATCH 28/34] x86/amd-iommu: Add device bind reference counting
    Date
    This patch adds a reference count to each device to count
    how often the device was bound to that domain. This is
    important for single devices that act as an alias for a
    number of others. These devices must stay bound to their
    domains until all devices that alias to it are unbound from
    the same domain.

    Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    ---
    arch/x86/include/asm/amd_iommu_types.h | 1 +
    arch/x86/kernel/amd_iommu.c | 37 +++++++++++++++++++++++++-------
    2 files changed, 30 insertions(+), 8 deletions(-)

    diff --git a/arch/x86/include/asm/amd_iommu_types.h b/arch/x86/include/asm/amd_iommu_types.h
    index 9eaa27b..434e90e 100644
    --- a/arch/x86/include/asm/amd_iommu_types.h
    +++ b/arch/x86/include/asm/amd_iommu_types.h
    @@ -253,6 +253,7 @@ struct protection_domain {
    struct iommu_dev_data {
    struct device *alias; /* The Alias Device */
    struct protection_domain *domain; /* Domain the device is bound to */
    + atomic_t bind; /* Domain attach reverent count */
    };

    /*
    diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
    index 3214e88..f5db7d5 100644
    --- a/arch/x86/kernel/amd_iommu.c
    +++ b/arch/x86/kernel/amd_iommu.c
    @@ -152,6 +152,8 @@ static int iommu_init_device(struct device *dev)
    if (pdev)
    dev_data->alias = &pdev->dev;

    + atomic_set(&dev_data->bind, 0);
    +
    dev->archdata.iommu = dev_data;


    @@ -1403,10 +1405,13 @@ static int __attach_device(struct device *dev,
    return -EBUSY;

    /* Do real assignment */
    - if (alias != devid &&
    - alias_data->domain == NULL) {
    - alias_data->domain = domain;
    - set_dte_entry(alias, domain);
    + if (alias != devid) {
    + if (alias_data->domain == NULL) {
    + alias_data->domain = domain;
    + set_dte_entry(alias, domain);
    + }
    +
    + atomic_inc(&alias_data->bind);
    }

    if (dev_data->domain == NULL) {
    @@ -1414,6 +1419,8 @@ static int __attach_device(struct device *dev,
    set_dte_entry(devid, domain);
    }

    + atomic_inc(&dev_data->bind);
    +
    /* ready */
    spin_unlock(&domain->lock);

    @@ -1449,20 +1456,34 @@ static int attach_device(struct device *dev,
    */
    static void __detach_device(struct device *dev)
    {
    - u16 devid = get_device_id(dev);
    + u16 devid = get_device_id(dev), alias;
    struct amd_iommu *iommu = amd_iommu_rlookup_table[devid];
    struct iommu_dev_data *dev_data = get_dev_data(dev);
    + struct iommu_dev_data *alias_data;

    BUG_ON(!iommu);

    - clear_dte_entry(devid);
    - dev_data->domain = NULL;
    + devid = get_device_id(dev);
    + alias = get_device_id(dev_data->alias);
    +
    + if (devid != alias) {
    + alias_data = get_dev_data(dev_data->alias);
    + if (atomic_dec_and_test(&alias_data->bind)) {
    + clear_dte_entry(alias);
    + alias_data->domain = NULL;
    + }
    + }
    +
    + if (atomic_dec_and_test(&dev_data->bind)) {
    + clear_dte_entry(devid);
    + dev_data->domain = NULL;
    + }

    /*
    * If we run in passthrough mode the device must be assigned to the
    * passthrough domain if it is detached from any other domain
    */
    - if (iommu_pass_through)
    + if (iommu_pass_through && dev_data->domain == NULL)
    __attach_device(dev, pt_domain);
    }

    --
    1.6.5.3



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