VFIO on ARM64

VFIO on ARM64

[valmiki]

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.
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 ?


Regards,
Valmiki

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Re: VFIO on ARM64

[Alex Williamson]

[Cc +Eric Auger]

On Tue, 12 Sep 2017 23:31:00 +0530
valmiki <valmikibow-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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.
> 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 ?
> 
> 
> Regards,
> Valmiki

Re: VFIO on ARM64

[Jean-Philippe Brucker]

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/*"?

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.

Thanks,
Jean

Re: VFIO on ARM64

[valmiki]

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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Re: VFIO on ARM64

[Jean-Philippe Brucker]

On 13/09/17 18:38, valmiki wrote:
> 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 ?

(I'm assuming you're using device-tree since you mentioned it in your
initial post.) Are you using the iommu-map property in your root complex
node? The "iommus" property in device-tree nodes defines one or more
static SIDs of a device, and doesn't work with PCI. iommu-map is a
wildcard for the whole PCI bus. It defines how PCI Requester IDs are
translated to SIDs. See Documentation/devicetree/bindings/pci/pci-iommu.txt

Thanks,
Jean

Invalidation in SMMU v3

[valmiki]

Hi Jean,

In PASID flow arm_smmu_atc_inv_master_all is called where size and iova 
of arm_smmu_atc_inv_to_cmd are zero and  no address is being filled in 
struct arm_smmu_cmdq_ent->atc.addr.
So how will smmu hardware know if there are any ats translations 
requested or not ?
How invalidation are carried out in PASID flow w.r.t address and size?


Regards,
Valmiki

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Re: Invalidation in SMMU v3

[Jean-Philippe Brucker]

Hi Valmiki,

On 03/12/17 13:56, valmiki wrote:
> Hi Jean,
> 
> In PASID flow arm_smmu_atc_inv_master_all is called where size and iova 
> of arm_smmu_atc_inv_to_cmd are zero and  no address is being filled in 
> struct arm_smmu_cmdq_ent->atc.addr.
> So how will smmu hardware know if there are any ats translations 
> requested or not ?
> How invalidation are carried out in PASID flow w.r.t address and size?

arm_smmu_atc_inv_master_all() is used to invalidate the whole address
space, for example when unbinding a process address space from the master.

The encoding is a bit special: when addr and size are 0,
arm_smmu_atc_inv_to_cmd() sets cmd->atc.size to 52, which according to the
SMMUv3 spec corresponds to a 2^64 byte span, meaning invalidate all. The
SMMU then converts this command into a PCIe ATC invalidation (with bits
62:12 all 1b and bit 63 = 0b, according to the ATS spec 2.3.2)

Smaller invalidations will go via arm_smmu_atc_inv_domain(), and
arm_smmu_atc_inv_to_cmd() will compute the appropriate range that covers
the requested address and size.

In more details, when a range is unmapped from a process (with munmap()
for example), the MMU notifier calls our invalidate_range() callback,
which calls arm_smmu_atc_inv_domain() with the right PASID. When a process
exits or unbind() is called, we use arm_smmu_atc_inv_master_all() with its
PASID.

Thanks,
Jean