Re: [RFC v5 7/7] vfio-pci: Allow to mmap MSI-X table if interrupt remapping is supported

[Eric Auger]

Hi Yongji,
On 04/07/2016 01:38 PM, Yongji Xie wrote:
> On 2016/4/6 22:45, Alex Williamson wrote:
>> On Tue,  5 Apr 2016 21:46:44 +0800
>> Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx> wrote:
>>
>>> This patch enables mmapping MSI-X tables if
>>> hardware supports interrupt remapping which
>>> can ensure that a given pci device can only
>>> shoot the MSIs assigned for it.
>>>
>>> Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
>>> ---
>>>   drivers/vfio/pci/vfio_pci.c         |    9 +++++++--
>>>   drivers/vfio/pci/vfio_pci_private.h |    1 +
>>>   drivers/vfio/pci/vfio_pci_rdwr.c    |    2 +-
>>>   3 files changed, 9 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>>> index c60d790..ef02896 100644
>>> --- a/drivers/vfio/pci/vfio_pci.c
>>> +++ b/drivers/vfio/pci/vfio_pci.c
>>> @@ -201,6 +201,10 @@ static int vfio_pci_enable(struct
>>> vfio_pci_device *vdev)
>>>       } else
>>>           vdev->msix_bar = 0xFF;
>>>   +    if (iommu_capable(pdev->dev.bus, IOMMU_CAP_INTR_REMAP) ||
>> This doesn't address the issue I raised earlier where ARM SMMU sets
>> this capability, but doesn't really provide per vector isolation.  ARM
>> either needs to be fixed or we need to consider the whole capability
>> tainted for this application and standardize around the bus flags.
>> It's not very desirable to have two different ways to test this anyway.
> 
> I saw Eric posted a patchset [1] which introduce a flag
> MSI_FLAG_IRQ_REMAPPING to indicate the capability
> for ARM SMMU. With this patchset applied, it would
> be  workable to use bus_flags to test the capability
> of ARM SMMU:

My purpose was to remove the advertising of IOMMU_CAP_INTR_REMAP from
arm-smmu.c, "fix" mentionned by Alex (by the way I also need to do the
same in v3 code) and to advertise the functionality on MSI controller
instead (since the IRQ REMAPPING functionality is abstracted in GICv3
ITS MSI controller)

On top of that, on ARM we have platform (non PCI) MSI controllers so my
understanding is the capability advertising should be possible beyond
the PCI bus?

Best Regards

Eric
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index a080f44..b2d1756 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1134,6 +1134,21 @@ void *msi_desc_to_pci_sysdata(struct msi_desc *desc)
>  }
>  EXPORT_SYMBOL_GPL(msi_desc_to_pci_sysdata);
> 
> +void pci_check_msi_remapping(struct pci_bus *bus)
> +{
> +#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
> +        struct irq_domain *domain;
> +        struct msi_domain_info *info;
> +
> +        domain = dev_get_msi_domain(&bus->dev);
> +        if (domain) {
> +                info = msi_get_domain_info(domain);
> +                if (info->flags & MSI_FLAG_IRQ_REMAPPING)
> +                        pdev->bus->bus_flags |= PCI_BUS_FLAGS_MSI_REMAP;
> +        }
> +#endif
> +}
> +
>  #ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
>  /**
>   * pci_msi_domain_write_msg - Helper to write MSI message to PCI config
> space
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 6d7ab9b..24e9606 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2115,6 +2115,7 @@ struct pci_bus *pci_create_root_bus(struct device
> *parent, int bus,
>         device_enable_async_suspend(b->bridge);
>         pci_set_bus_of_node(b);
>         pci_set_bus_msi_domain(b);
> +       pci_check_msi_remapping(b);
> 
>         if (!parent)
>                 set_dev_node(b->bridge, pcibus_to_node(b));
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index a2a0068..fe8ce7b 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -15,6 +15,7 @@ extern int pci_msi_ignore_mask;
>  struct irq_data;
>  struct msi_desc;
>  struct pci_dev;
> +struct pci_bus;
>  struct platform_msi_priv_data;
>  void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
>  void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
> @@ -155,6 +156,8 @@ void arch_restore_msi_irqs(struct pci_dev *dev);
>  void default_teardown_msi_irqs(struct pci_dev *dev);
>  void default_restore_msi_irqs(struct pci_dev *dev);
> 
> +void pci_check_msi_remapping(struct pci_bus *bus);
> +
>  struct msi_controller {
>         struct module *owner;
>         struct device *dev;
> 
> Next we just need to find a proper way to make
> bus_flags compatible with IOMMU_CAP_INTR_REMAP, right?
> 
> I think a good place to do that is add_iommu_group().
> But I'm not sure whether iommu drivers must be
> initialized after PCI enumeration.  Do you have any comment?
> 
> [1] http://www.spinics.net/lists/kvm/msg130256.html
> 
>>> +        pdev->bus->bus_flags | PCI_BUS_FLAGS_MSI_REMAP)
>> Perhaps some sort of wrapper for testing these flags would help avoid
>> this kind of coding error (| vs &)
> 
> Thank you.  I'll try not to make the same mistake again.
> 
> Regards,
> Yongji
>