Baolu:

Thanks for your comments and your patch. Please find below our responses to

each of your comments:

> What does "I/O operation won't work" exactly mean here? Do you see any

> IOMMU fault message? Or, something doesn't work as expected?

Yes, DMAR fault messages as following came out:

[ 354.939896] DMAR: DMAR:[DMA Read] Request device [03:00.1]fault addr 1fdfe80000

[ 354.939896] DMAR:[fault reason 02] Present bit in context entry is clear

> Do you mind checking this?

> index 6ecdcf8fc8c0..f62f30bc1339 100644

> --- a/drivers/iommu/intel-iommu.c

> +++ b/drivers/iommu/intel-iommu.c

> @@ -2632,6 +2632,9 @@ static struct dmar_domain

> *find_or_alloc_domain(struct device *dev, int gaw)

> goto out;

> }

> + if (!iommu_should_identity_map(dev, 0))

> + return si_domain;

> +

> /* Allocate and initialize new domain for the device */

> domain = alloc_domain(0);

> if (!domain)

Tried this patch, and the same DMAR fault message came out.

Guess it is because of the iommu code path for hotplug devices. If a hotplug

device is rescanned after removal, iommu_bus_notifier will be called as part

of the notifier chains to handle BUS_NOTIFY_ADD_DEVICE event. Along the code

path, intel_iommu_ops->add_device() created an iommu group for this hotplug

device, but failed to create an iommu domain because of the default domain

type IOMMU_DOMAIN_IDENTITY imposed by current IOMMU command line option got

declined by intel_iommu_ops->domain_alloc().

In your patch, function find_or_alloc_domain() is not even in the code path

of BUS_NOTIFY_ADD_DEVICE event notifier chain.

Please let us know if your have more concerns and suggestions.

Best Regards,

James

On Thu, Feb 21, 2019 at 9:35 PM Lu Baolu <baolu.lu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> wrote:

Hi

On 2/22/19 1:06 PM, Lu Baolu wrote:

> Do you mind checking this?
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 6ecdcf8fc8c0..f62f30bc1339 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -2632,6 +2632,9 @@ static struct dmar_domain
> *find_or_alloc_domain(struct device *dev, int gaw)
>                         goto out;
>         }
>
> +       if (!iommu_should_identity_map(dev, 0))
> +               return si_domain;
> +
>         /* Allocate and initialize new domain for the device */
>         domain = alloc_domain(0);
>         if (!domain)

Oops! This can't be compiled. Please try below instead if you'd like to.
Sorry about it.

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 6ecdcf8fc8c0..b89f5ba6a3c8 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -174,6 +174,8 @@ static inline unsigned long virt_to_dma_pfn(void *p)
return page_to_dma_pfn(virt_to_page(p));
}

+static int iommu_should_identity_map(struct device *dev, int startup);
+
/* global iommu list, set NULL for ignored DMAR units */
static struct intel_iommu **g_iommus;

@@ -2632,6 +2634,9 @@ static struct dmar_domain
*find_or_alloc_domain(struct device *dev, int gaw)
goto out;
}

+ if (iommu_should_identity_map(dev, 0))
+ return si_domain;
+
/* Allocate and initialize new domain for the device */
domain = alloc_domain(0);
if (!domain)

Best regards,
Lu Baolu