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SubjectRe: [PATCH] iommu/vt-d: fix RCU-list bugs in intel_iommu_init
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Hi,

On 2020/3/6 4:00, Qian Cai wrote:
> There are several places traverse RCU-list without holding any lock in
> intel_iommu_init(). Fix them by acquiring dmar_global_lock.
>
> WARNING: suspicious RCU usage
> -----------------------------
> drivers/iommu/intel-iommu.c:5216 RCU-list traversed in non-reader section!!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> no locks held by swapper/0/1.
>
> Call Trace:
> dump_stack+0xa0/0xea
> lockdep_rcu_suspicious+0x102/0x10b
> intel_iommu_init+0x947/0xb13
> pci_iommu_init+0x26/0x62
> do_one_initcall+0xfe/0x500
> kernel_init_freeable+0x45a/0x4f8
> kernel_init+0x11/0x139
> ret_from_fork+0x3a/0x50
> DMAR: Intel(R) Virtualization Technology for Directed I/O
>
> Fixes: d8190dc63886 ("iommu/vt-d: Enable DMA remapping after rmrr mapped")
> Signed-off-by: Qian Cai <cai@lca.pw>

Thanks for the fix.

Acked-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu

> ---
> drivers/iommu/intel-iommu.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 6fa6de2b6ad5..bc138ceb07bc 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5193,6 +5193,7 @@ int __init intel_iommu_init(void)
>
> init_iommu_pm_ops();
>
> + down_read(&dmar_global_lock);
> for_each_active_iommu(iommu, drhd) {
> iommu_device_sysfs_add(&iommu->iommu, NULL,
> intel_iommu_groups,
> @@ -5200,6 +5201,7 @@ int __init intel_iommu_init(void)
> iommu_device_set_ops(&iommu->iommu, &intel_iommu_ops);
> iommu_device_register(&iommu->iommu);
> }
> + up_read(&dmar_global_lock);
>
> bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
> if (si_domain && !hw_pass_through)
> @@ -5210,7 +5212,6 @@ int __init intel_iommu_init(void)
> down_read(&dmar_global_lock);
> if (probe_acpi_namespace_devices())
> pr_warn("ACPI name space devices didn't probe correctly\n");
> - up_read(&dmar_global_lock);
>
> /* Finally, we enable the DMA remapping hardware. */
> for_each_iommu(iommu, drhd) {
> @@ -5219,6 +5220,8 @@ int __init intel_iommu_init(void)
>
> iommu_disable_protect_mem_regions(iommu);
> }
> + up_read(&dmar_global_lock);
> +
> pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
>
> intel_iommu_enabled = 1;
>

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