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Message-ID: <e2698dbe-18e2-1a82-8a12-fe45bc9be534@arm.com>
Date:   Fri, 4 Mar 2022 14:10:55 +0000
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Subject: Re: [PATCH v7 01/11] iommu: Add DMA ownership management interfaces
Content-Language: en-GB
To:     eric.auger@redhat.com, Lu Baolu <baolu.lu@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Joerg Roedel <joro@8bytes.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>
Cc:     Chaitanya Kulkarni <kch@nvidia.com>, kvm@vger.kernel.org,
        Stuart Yoder <stuyoder@gmail.com>, rafael@kernel.org,
        David Airlie <airlied@linux.ie>, linux-pci@vger.kernel.org,
        Cornelia Huck <cohuck@redhat.com>,
        linux-kernel@vger.kernel.org,
        Jonathan Hunter <jonathanh@nvidia.com>,
        iommu@lists.linux-foundation.org,
        Thierry Reding <thierry.reding@gmail.com>,
        Jacob jun Pan <jacob.jun.pan@intel.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Diana Craciun <diana.craciun@oss.nxp.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Li Yang <leoyang.li@nxp.com>, Will Deacon <will@kernel.org>,
        Dmitry Osipenko <digetx@gmail.com>
References: <20220228005056.599595-1-baolu.lu@linux.intel.com>
 <20220228005056.599595-2-baolu.lu@linux.intel.com>
 <c75b6e04-bc1b-b9f6-1a44-bf1567a8c19d@redhat.com>
 <7a3dc977-0c5f-6d88-6d3a-8e49bc717690@linux.intel.com>
 <1648bc97-a0d3-4051-58d0-e24fa9e9d183@arm.com>
 <350a8e09-08a9-082b-3ad1-b711c7d98d73@redhat.com>
From:   Robin Murphy <robin.murphy@arm.com>
In-Reply-To: <350a8e09-08a9-082b-3ad1-b711c7d98d73@redhat.com>
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Precedence: bulk

On 2022-03-04 13:55, Eric Auger wrote:
> Hi Robin,
> 
> On 3/4/22 1:22 PM, Robin Murphy wrote:
>> On 2022-03-04 10:43, Lu Baolu wrote:
>>> Hi Eric,
>>>
>>> On 2022/3/4 18:34, Eric Auger wrote:
>>>> I hit a WARN_ON() when unbinding an e1000e driver just after boot:
>>>>
>>>> sudo modprobe -v vfio-pci
>>>> echo vfio-pci | sudo tee -a
>>>> /sys/bus/pci/devices/0004:01:00.0/driver_override
>>>> vfio-pci
>>>> echo 0004:01:00.0 | sudo tee -a  /sys/bus/pci/drivers/e1000e/unbind
>>>>
>>>>
>>>> [  390.042811] ------------[ cut here ]------------
>>>> [  390.046468] WARNING: CPU: 42 PID: 5589 at drivers/iommu/iommu.c:3123
>>>> iommu_device_unuse_default_domain+0x68/0x100
>>>> [  390.056710] Modules linked in: vfio_pci vfio_pci_core vfio_virqfd
>>>> vfio_iommu_type1 vfio xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT
>>>> nf_reject_ipv4 nft_compat nft_chain_nat nf_nat nf_conntrack
>>>> nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink bridge stp llc rfkill
>>>> sunrpc vfat fat mlx5_ib ib_uverbs ib_core acpi_ipmi ipmi_ssif
>>>> ipmi_devintf ipmi_msghandler cppc_cpufreq drm xfs libcrc32c
>>>> mlx5_core sg
>>>> mlxfw crct10dif_ce tls ghash_ce sha2_ce sha256_arm64 sha1_ce sbsa_gwdt
>>>> e1000e psample sdhci_acpi ahci_platform sdhci libahci_platform
>>>> qcom_emac
>>>> mmc_core hdma hdma_mgmt dm_mirror dm_region_hash dm_log dm_mod fuse
>>>> [  390.110618] CPU: 42 PID: 5589 Comm: tee Kdump: loaded Not tainted
>>>> 5.17.0-rc4-lu-v7-official+ #24
>>>> [  390.119384] Hardware name: WIWYNN QDF2400 Reference Evaluation
>>>> Platform CV90-LA115-P120/QDF2400 Customer Reference Board, BIOS
>>>> 0ACJA570
>>>> 11/05/2018
>>>> [  390.132492] pstate: a0400005 (NzCv daif +PAN -UAO -TCO -DIT -SSBS
>>>> BTYPE=--)
>>>> [  390.139436] pc : iommu_device_unuse_default_domain+0x68/0x100
>>>> [  390.145165] lr : iommu_device_unuse_default_domain+0x38/0x100
>>>> [  390.150894] sp : ffff80000fbb3bc0
>>>> [  390.154193] x29: ffff80000fbb3bc0 x28: ffff03c0cf6b2400 x27:
>>>> 0000000000000000
>>>> [  390.161311] x26: 0000000000000000 x25: 0000000000000000 x24:
>>>> ffff03c0c7cc5720
>>>> [  390.168429] x23: ffff03c0c2b9d150 x22: ffffb4e61df223f8 x21:
>>>> ffffb4e61df223f8
>>>> [  390.175547] x20: ffff03c7c03c3758 x19: ffff03c7c03c3700 x18:
>>>> 0000000000000000
>>>> [  390.182665] x17: 0000000000000000 x16: 0000000000000000 x15:
>>>> 0000000000000000
>>>> [  390.189783] x14: 0000000000000000 x13: 0000000000000030 x12:
>>>> ffff03c0d519cd80
>>>> [  390.196901] x11: 7f7f7f7f7f7f7f7f x10: 0000000000000dc0 x9 :
>>>> ffffb4e620b54f8c
>>>> [  390.204019] x8 : ffff03c0cf6b3220 x7 : ffff4ef132bba000 x6 :
>>>> 00000000000000ff
>>>> [  390.211137] x5 : ffff03c0c2b9f108 x4 : ffff03c0d51f6438 x3 :
>>>> 0000000000000000
>>>> [  390.218255] x2 : ffff03c0cf6b2400 x1 : 0000000000000000 x0 :
>>>> 0000000000000000
>>>> [  390.225374] Call trace:
>>>> [  390.227804]  iommu_device_unuse_default_domain+0x68/0x100
>>>> [  390.233187]  pci_dma_cleanup+0x38/0x44
>>>> [  390.236919]  __device_release_driver+0x1a8/0x260
>>>> [  390.241519]  device_driver_detach+0x50/0xd0
>>>> [  390.245686]  unbind_store+0xf8/0x120
>>>> [  390.249245]  drv_attr_store+0x30/0x44
>>>> [  390.252891]  sysfs_kf_write+0x50/0x60
>>>> [  390.256537]  kernfs_fop_write_iter+0x134/0x1cc
>>>> [  390.260964]  new_sync_write+0xf0/0x18c
>>>> [  390.264696]  vfs_write+0x230/0x2d0
>>>> [  390.268082]  ksys_write+0x74/0x100
>>>> [  390.271467]  __arm64_sys_write+0x28/0x3c
>>>> [  390.275373]  invoke_syscall.constprop.0+0x58/0xf0
>>>> [  390.280061]  el0_svc_common.constprop.0+0x160/0x164
>>>> [  390.284922]  do_el0_svc+0x34/0xcc
>>>> [  390.288221]  el0_svc+0x30/0x140
>>>> [  390.291346]  el0t_64_sync_handler+0xa4/0x130
>>>> [  390.295599]  el0t_64_sync+0x1a0/0x1a4
>>>> [  390.299245] ---[ end trace 0000000000000000 ]---
>>>>
>>>>
>>>> I put some traces in the code and I can see that
>>>> iommu_device_use_default_domain() effectively is called on
>>>> 0004:01:00.0 e1000e device on pci_dma_configure() but at that time
>>>> the iommu group is NULL:
>>>> [   10.569427] e1000e 0004:01:00.0: ------ ENTRY pci_dma_configure
>>>> driver_managed_area=0
>>>> [   10.569431] e1000e 0004:01:00.0: ****
>>>> iommu_device_use_default_domain ENTRY
>>>> [   10.569433] e1000e 0004:01:00.0: ****
>>>> iommu_device_use_default_domain no group
>>>> [   10.569435] e1000e 0004:01:00.0: pci_dma_configure
>>>> iommu_device_use_default_domain returned 0
>>>> [   10.569492] e1000e 0004:01:00.0: Adding to iommu group 3
>>>>
>>>> ^^^the group is added after the
>>>> iommu_device_use_default_domain() call
>>>> So the group->owner_cnt is not incremented as expected.
>>>
>>> Thank you for reporting this. Do you have any idea why the driver is
>>> loaded before iommu_probe_device()?
>>
>> Urgh, this is the horrible firmware-data-ordering thing again. The
>> stuff I've been saying about having to rework the whole .dma_configure
>> mechanism in the near future is to fix this properly.
>>
>> The summary is that in patch #4, calling
>> iommu_device_use_default_domain() *before* {of,acpi}_dma_configure is
>> currently a problem. As things stand, the IOMMU driver ignored the
>> initial iommu_probe_device() call when the device was added, since at
>> that point it had no fwspec yet. In this situation,
>> {of,acpi}_iommu_configure() are retriggering iommu_probe_device()
>> after the IOMMU driver has seen the firmware data via .of_xlate to
>> learn that it it actually responsible for the given device.
> 
> thank you for providing the info. Hope this is something Lu can work around.

Hopefully it's just a case of flipping the calls around, so that 
iommu_use_default_domain() goes at the end, and calls 
arch_teardown_dma_ops() if it fails. From a quick skim I *think* that 
should still work out to the desired behaviour (or at least close enough 
that we can move forward without a circular dependency between fixes...)

Robin.