Re: iommu/vt-d: Cure VF irqdomain hickup

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi Thomas,

On 2020/11/13 3:15, Thomas Gleixner wrote:
> The recent changes to store the MSI irqdomain pointer in struct device
> missed that Intel DMAR does not register virtual function devices.  Due to
> that a VF device gets the plain PCI-MSI domain assigned and then issues
> compat MSI messages which get caught by the interrupt remapping unit.
> 
> Cure that by inheriting the irq domain from the physical function
> device.
> 
> That's a temporary workaround. The correct fix is to inherit the irq domain
> from the bus, but that's a larger effort which needs quite some other
> changes to the way how x86 manages PCI and MSI domains.
> 
> Fixes: 85a8dfc57a0b ("iommm/vt-d: Store irq domain in struct device")
> Reported-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>   drivers/iommu/intel/dmar.c |   19 ++++++++++++++++++-
>   1 file changed, 18 insertions(+), 1 deletion(-)
> 
> --- a/drivers/iommu/intel/dmar.c
> +++ b/drivers/iommu/intel/dmar.c
> @@ -333,6 +333,11 @@ static void  dmar_pci_bus_del_dev(struct
>   	dmar_iommu_notify_scope_dev(info);
>   }
>   
> +static inline void vf_inherit_msi_domain(struct pci_dev *pdev)
> +{
> +	dev_set_msi_domain(&pdev->dev, dev_get_msi_domain(&pdev->physfn->dev));
> +}
> +
>   static int dmar_pci_bus_notifier(struct notifier_block *nb,
>   				 unsigned long action, void *data)
>   {
> @@ -342,8 +347,20 @@ static int dmar_pci_bus_notifier(struct
>   	/* Only care about add/remove events for physical functions.
>   	 * For VFs we actually do the lookup based on the corresponding
>   	 * PF in device_to_iommu() anyway. */
> -	if (pdev->is_virtfn)
> +	if (pdev->is_virtfn) {
> +		/*
> +		 * Note: This is a horrible hack and needs to be cleaned
> +		 * up by assigning the domain to the bus, but that's too
> +		 * big of a change for post rc3.
> +		 *
> +		 * Ensure that the VF device inherits the irq domain of the
> +		 * PF device:
> +		 */
> +		if (action == BUS_NOTIFY_ADD_DEVICE)
> +			vf_inherit_msi_domain(pdev);
>   		return NOTIFY_DONE;
> +	}
> +
>   	if (action != BUS_NOTIFY_ADD_DEVICE &&
>   	    action != BUS_NOTIFY_REMOVED_DEVICE)
>   		return NOTIFY_DONE;

We also encountered this problem in internal testing. This patch can
solve the problem.

Acked-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu
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