On 9/13/2017 6:50 AM, Jean-Philippe Brucker wrote:
Hi Valmiki,
On 12/09/17 19:01, valmiki wrote:
Hi, as per VFIO documentation i see that we need to see
"/sys/bus/pci/devices/0000:06:0d.0/iommu_group" in order to find group
in which PCI bus is attached.
But as per drivers/pci/pci-sysfs.c in static struct attribute
*pci_dev_attrs[], i don't see any such attribute.
This iommu_group attribute is created by
drivers/iommu/iommu.c:iommu_group_add_device. It is a symbolic link to
/sys/kernel/iommu_groups/<group>.
I tried enabling SMMUv2 driver and SMMU for PCIe node on our SOC, but
this file doesn't show up and also in /sys/kernel/iommu_group i do not
see "/sys/kernel/iommu_groups/17/devices/0000:00:1f.00" file, i see only
PCIe root port device tree node in that group and not individual buses.
So on ARM64 for showing these paths i.e show specific to each bus, does
SMMU need any particular confguration (we have SMMUv2) > Do we need any specific kernel configuration ?
I don't think so. If you're able to see the root complex in an IOMMU
group, then the configuration is probably fine. Could you provide a little
more information about your system, for example lspci along with "find
/sys/kernel/iommu_groups/*/devices/*"?
Here is the log:
root@:~# lspci
00:00.0 PCI bridge: Corporation Device a023
01:00.0 Memory controller: Corporation Device a024
root@:~# find /sys/kernel/iommu_groups/*/devices/*
/sys/kernel/iommu_groups/0/devices/ad0c0000.pcie
/sys/kernel/iommu_groups/1/devices/ad0f0000.spi
/sys/kernel/iommu_groups/2/devices/adc70000.sdhci
/sys/kernel/iommu_groups/3/devices/ad9d0000.usb0
root@:~#
Ideally, each PCIe device will be in its own IOMMU group. So you shouldn't
have each bus in a group, but rather one device per group. Linux puts
multiple devices in a group if the IOMMU cannot properly isolate them. In
general it's not something you want in your system, because all devices in
a group will have the same address space and cannot be passed to a guest
separately.
So i don't see separate group per pci device.When you say one pci device
per group, when does smmu creates one group per pci device ?
As per boot log i see that smmu drvier gets probed first and then pcie
root port driver, so how will smmu know number of pci devices present
downstream and create a group for each device ?
Regards,
Valmiki
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