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SubjectRe: [RFC v5 7/7] vfio-pci: Allow to mmap MSI-X table if interrupt remapping is supported
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On 2016/4/6 22:45, Alex Williamson wrote:
> On Tue, 5 Apr 2016 21:46:44 +0800
> Yongji Xie <xyjxie@linux.vnet.ibm.com> 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@linux.vnet.ibm.com>
>> ---
>> 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:

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

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