Re: [Xen-devel] [PATCH v13 3/3] IOMMU: fix vt-d Device-TLB flush timeout issue

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Xu, Quan
> Sent: Wednesday, June 29, 2016 2:00 PM
> 
> From: Quan Xu <quan.xu@xxxxxxxxx>
> 
> If Device-TLB flush timed out, we hide the target ATS device
> immediately. By hiding the device, we make sure it can't be
> assigned to any domain any longer (see device_assigned).
> 
> Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
> 
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
> CC: Feng Wu <feng.wu@xxxxxxxxx>
> 
> ---
> v13:
>    1. drop domain crash logic, which is added to the vendor
>       independent layer in patch #2.
>    2. rename dev_invalidate_iotlb_timeout() to iommu_dev_iotlb_flush_timeout()
>       and move it to the vendor independent layer.
> ---
>  xen/drivers/passthrough/iommu.c       | 21 +++++++++++++
>  xen/drivers/passthrough/pci.c         |  6 ++--
>  xen/drivers/passthrough/vtd/extern.h  |  5 ++--
>  xen/drivers/passthrough/vtd/qinval.c  | 56
> +++++++++++++++++++++++++++--------
>  xen/drivers/passthrough/vtd/x86/ats.c | 11 ++-----
>  xen/include/xen/iommu.h               |  3 ++
>  xen/include/xen/pci.h                 |  1 +
>  7 files changed, 76 insertions(+), 27 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
> index d793f5d..5db8ae6 100644
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -361,6 +361,27 @@ int iommu_iotlb_flush_all(struct domain *d)
>      return rc;
>  }
> 
> +void iommu_dev_iotlb_flush_timeout(struct domain *d,
> +                                   struct pci_dev *pdev)
> +{
> +    pcidevs_lock();
> +
> +    ASSERT(pdev->domain);
> +    if ( d != pdev->domain )
> +        return;

return w/o releasing the lock!

and is above scenario actually possible (a flush timeout is captured when
the device doesn't belong to previous domain)? If not, better to move
the condition into ASSERT.

> +
> +    list_del(&pdev->domain_list);
> +    pdev->domain = NULL;
> +    pci_hide_existing_device(pdev);
> +    if ( !d->is_shutting_down && printk_ratelimit() )
> +        printk(XENLOG_ERR
> +               "dom%d: ATS device %04x:%02x:%02x.%u flush failed\n",
> +               d->domain_id, pdev->seg, pdev->bus, PCI_SLOT(pdev->devfn),
> +               PCI_FUNC(pdev->devfn));
> +
> +    pcidevs_unlock();

please move above warning out of the lock.

Thanks
Kevin

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