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Message-ID: <038397a6-57e2-b6fc-6e1c-7c03b7be9d96@huawei.com>
Date: Mon, 28 Jun 2021 21:20:41 +0800
From: Xingang Wang <wangxingang5@...wei.com>
To: Bjorn Helgaas <helgaas@...nel.org>
CC: <robh@...nel.org>, <will@...nel.org>, <joro@...tes.org>,
<robh+dt@...nel.org>, <gregkh@...uxfoundation.org>,
<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
<linux-pci@...r.kernel.org>, <xieyingtai@...wei.com>,
John Garry <john.garry@...wei.com>,
Auger Eric <eric.auger@...hat.com>,
"jean-philippe@...aro.org" <jean-philippe@...aro.org>
Subject: Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating PCI
devices
Hi Bjorn,
I would like to add more explanation about what problem this patch
fixed.
I am testing the SVA/vSVA series patches written by @Jean and @Brucker.
I test with the following qemu command line, with a hisilicon SEC device
attached on a pcie-root-port.
$QEMU/qemu-system-aarch64 \
-enable-kvm \
-kernel $LINUX/arch/arm64/boot/Image \
-m 16G \
-smp cores=8,threads=1,sockets=2 \
-machine virt,kernel_irqchip=on,gic-version=3,iommu=smmuv3 \
-device
pcie-root-port,port=0x8,chassis=1,id=pci.1,bus=pcie.0,addr=0x1 \
-device vfio-pci,host=75:00.0,bus=pci.1,addr=0x0,id=acc2 \
-net none \
-initrd ./mfs.cpio.gz \
-cpu host \
-nographic \
-append "rdinit=init console=ttyAMA0 earlycon=pl011,0x9000000" \
And I got the guest PCI configuration:
00:00.0 Class 0600: Device 1b36:0008 # root bus
00:01.0 Class 0604: Device 1b36:000c # root port
Capabilities: [148 v1] Access Control Services
ACSCap: SrcValid+ TransBlk+ ReqRedir+ CmpltRedir+ UpstreamFwd+
EgressCtrl- DirectTrans+
ACSCtl: SrcValid- TransBlk- ReqRedir- CmpltRedir- UpstreamFwd-
EgressCtrl- DirectTrans-
Kernel driver in use: pcieport
01:00.0 Class 1000: Device 19e5:a255 (rev 21) # SEC
The PCI configuration shows that the ACS of the pcie root port is
not enabled, while it should have.
Then when I insmod device driver and init the SVA feature, I got
[ 24.342450] hisi_sec2 0000:01:00.0: cannot attach to incompatible
domain (0 SSID bits != 10)
[ 24.343731] hisi_sec2 0000:01:00.0: Failed to add to iommu group 0: -22
[ 24.345243] hisi_sec2 0000:01:00.0: enabling device (0000 -> 0002)
qemu-system-aarch64: vfio_enable_vectors failed to register S1 MSI
binding for vector 0(-2)
qemu-system-aarch64: vfio: Error: Failed to setup MSI fds: Interrupted
system call
qemu-system-aarch64: vfio: Error: Failed to enable MSI
I figured out that this error occurs in the arm_smmu_attach_dev
when checking ssid_bits for SVA feature,
the master->ssid_bits != smmu_domain->s1_cfg.s1cdmax caused this
problem. This is becuase the ACS of pcie-root-port is not enabled, the
pcie-root-port and SEC device share the same domain.
And SEC's ssid_bits is 10, while pcie-root-port's s1cdmax is zero, this
cause the problem.
And about why the ACS is not enabled in kernel, I have explained as the
following:
On 2021/6/7 20:58, Xingang Wang wrote:
> On 2021/6/5 3:04, Bjorn Helgaas wrote:
>> [+cc John, who tested 6bf6c24720d3]
>>
>> On Fri, May 21, 2021 at 03:03:24AM +0000, Wang Xingang wrote:
>>> From: Xingang Wang <wangxingang5@...wei.com>
>>>
>>> When booting with devicetree, the pci_request_acs() is called after the
>>> enumeration and initialization of PCI devices, thus the ACS is not
>>> enabled. And ACS should be enabled when IOMMU is detected for the
>>> PCI host bridge, so add check for IOMMU before probe of PCI host and
>>> call
>>> pci_request_acs() to make sure ACS will be enabled when enumerating PCI
>>> devices.
>>
>> I'm happy to apply this, but I'm a little puzzled about 6bf6c24720d3
>> ("iommu/of: Request ACS from the PCI core when configuring IOMMU
>> linkage"). It was tested and fixed a problem, but I don't understand
>> how.
>>
>> 6bf6c24720d3 added the call to pci_request_acs() in
>> of_iommu_configure() so it currently looks like this:
>>
>> of_iommu_configure(dev, ...)
>> {
>> if (dev_is_pci(dev))
>> pci_request_acs();
>>
>> pci_request_acs() sets pci_acs_enable, which tells us to enable ACS
>> when enumerating PCI devices in the future. But we only call
>> pci_request_acs() if we already *have* a PCI device.
>>
>> So maybe 6bf6c24720d3 fixed a problem for *some* PCI devices, but not
>> all? E.g., did we call of_iommu_configure() for one PCI device before
>> enumerating the rest?
>>
> I test the kernel on an arm platform with qemu:
>
> qemu-system-aarch64 \
> -cpu host \
> -kernel arch/arm64/boot/Image \
> -enable-kvm \
> -m 8G \
> -smp 2,sockets=2,cores=1,threads=1 \
> -machine virt,kernel_irqchip=on,gic-version=3,iommu=smmuv3\
> -initrd rootfs.cpio.gz \
> -nographic \
> -append "rdinit=init console=ttyAMA0 earlycon=pl011,0x9000000 nokaslr" \
> -device pcie-root-port,port=0x1,chassis=1,id=pci.1,addr=0x8 \
> -netdev user,id=hostnet0 \
> -device
> virtio-net-pci,netdev=hostnet0,id=net0,mac=08:13:3a:5a:22:5b,bus=pci.1,addr=0x0
> \
>
> And find that the of_iommu_configure is called after the enumeration
> of the pcie-root-port. And this might only infect the first device, when
> enumerating
> the rest devices, the pci_acs_enable has already be enabled.
>
> But to make sure that the pci_acs_enable will always be set before all
> PCI devices,
> it would be better to set it in initialization of PCI bridges.
>
> Thanks
>
> Xingang
>
>>> Fixes: 6bf6c24720d33 ("iommu/of: Request ACS from the PCI core when
>>> configuring IOMMU linkage")
>>> Signed-off-by: Xingang Wang <wangxingang5@...wei.com>
>>> ---
>>> drivers/iommu/of_iommu.c | 1 -
>>> drivers/pci/of.c | 8 +++++++-
>>> 2 files changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
>>> index a9d2df001149..54a14da242cc 100644
>>> --- a/drivers/iommu/of_iommu.c
>>> +++ b/drivers/iommu/of_iommu.c
>>> @@ -205,7 +205,6 @@ const struct iommu_ops *of_iommu_configure(struct
>>> device *dev,
>>> .np = master_np,
>>> };
>>> - pci_request_acs();
>>> err = pci_for_each_dma_alias(to_pci_dev(dev),
>>> of_pci_iommu_init, &info);
>>> } else {
>>> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
>>> index da5b414d585a..2313c3f848b0 100644
>>> --- a/drivers/pci/of.c
>>> +++ b/drivers/pci/of.c
>>> @@ -581,9 +581,15 @@ static int
>>> pci_parse_request_of_pci_ranges(struct device *dev,
>>> int devm_of_pci_bridge_init(struct device *dev, struct
>>> pci_host_bridge *bridge)
>>> {
>>> - if (!dev->of_node)
>>> + struct device_node *node = dev->of_node;
>>> +
>>> + if (!node)
>>> return 0;
>>> + /* Detect IOMMU and make sure ACS will be enabled */
>>> + if (of_property_read_bool(node, "iommu-map"))
>>> + pci_request_acs();
>>> +
>>> bridge->swizzle_irq = pci_common_swizzle;
>>> bridge->map_irq = of_irq_parse_and_map_pci;
>>> --
>>> 2.19.1
>>>
>> .
>>
>
> .
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