Re: [PATCH] irqchip/gic-{v2m, v3-its}: check iommu capable before doing iommu map

[Shawn Lin]

Hi Marc

On 2017/8/17 16:52, Marc Zyngier wrote:
> On 17/08/17 09:28, Shawn Lin wrote:
> > If a PCIe RC use gic-v2m or gic-v3-its as a msi domain but doesn't
> > have iommu support, we don't need to do iommu_dma_map_msi_msg to
> > get mapped iommu address as all we need is the physical address.
> > Otherwise we see the oops shown below as we can't get a iommu_group
> > for a device without iommu capable.
> >
> > Unable to handle kernel NULL pointer dereference at virtual address
> > 000000d0
> > [00000000000000d0] user address but active_mm is swapper
> > Internal error: Oops: 96000004 [#1] PREEMPT SMP
> > Modules linked in:
> > CPU: 3 PID: 1 Comm: swapper/0 Not tainted
> > 4.13.0-rc5-next-20170815-00001-g0744890-dirty #53
> > Hardware name: Firefly-RK3399 Board (DT)
> > task: ffff80007bc70000 task.stack: ffff80007bc6c000
> > PC is at iommu_get_domain_for_dev+0x38/0x50
> > LR is at iommu_dma_map_msi_msg+0x3c/0x1b8
> > pc : [<ffff000008569210>] lr : [<ffff00000856c1e4>] pstate:
> > a0000045
> >
> > ...
> >
> > [<ffff000008569210>] iommu_get_domain_for_dev+0x38/0x50
> > [<ffff00000856c1e4>] iommu_dma_map_msi_msg+0x3c/0x1b8
> > [<ffff0000083d4d8c>] its_irq_compose_msi_msg+0x44/0x50
> > [<ffff00000811be50>] irq_chip_compose_msi_msg+0x40/0x58
> > [<ffff000008120e34>] msi_domain_activate+0x1c/0x48
> > [<ffff00000811d9f8>] __irq_domain_activate_irq+0x40/0x58
> > [<ffff00000811f724>] irq_domain_activate_irq+0x24/0x40
> > [<ffff00000812139c>] msi_domain_alloc_irqs+0x104/0x190
> > [<ffff000008445abc>] pci_msi_setup_msi_irqs+0x3c/0x48
> > [<ffff00000844658c>] __pci_enable_msi_range+0x21c/0x408
> > [<ffff0000084468a4>] pci_alloc_irq_vectors_affinity+0x104/0x168
> > [<ffff00000843cd98>] pcie_port_device_register+0x200/0x488
> > [<ffff00000843d2ac>] pcie_portdrv_probe+0x34/0xd0
> > [<ffff00000842e2cc>] local_pci_probe+0x3c/0xb8
> > [<ffff00000842f5f8>] pci_device_probe+0x138/0x170
> > [<ffff00000857d964>] driver_probe_device+0x21c/0x2d8
> > [<ffff00000857db6c>] __device_attach_driver+0x9c/0xf8
> > [<ffff00000857bbfc>] bus_for_each_drv+0x5c/0x98
> > [<ffff00000857d61c>] __device_attach+0xc4/0x138
> > [<ffff00000857d6a0>] device_attach+0x10/0x18
> > [<ffff00000842395c>] pci_bus_add_device+0x4c/0xa8
> > [<ffff0000084239fc>] pci_bus_add_devices+0x44/0x90
> > [<ffff000008451e88>] rockchip_pcie_probe+0xc70/0xcc8
> > [<ffff00000857f738>] platform_drv_probe+0x58/0xc0
> > [<ffff00000857d964>] driver_probe_device+0x21c/0x2d8
> > [<ffff00000857dacc>] __driver_attach+0xac/0xb0
> > [<ffff00000857bb3c>] bus_for_each_dev+0x64/0xa0
> > [<ffff00000857d258>] driver_attach+0x20/0x28
> > [<ffff00000857cd08>] bus_add_driver+0x110/0x230
> > [<ffff00000857e468>] driver_register+0x60/0xf8
> > [<ffff00000857f690>] __platform_driver_register+0x40/0x48
> > [<ffff000008dd6dc0>] rockchip_pcie_driver_init+0x18/0x20
> > [<ffff000008083970>] do_one_initcall+0xb0/0x120
> > [<ffff000008db0cfc>] kernel_init_freeable+0x184/0x224
> > [<ffff00000896fce8>] kernel_init+0x10/0x100
> > [<ffff000008084ad0>] ret_from_fork+0x10/0x18
> >
> > This patch is to fix the problem exposed by the commit mentioned below.
> > Before this commit, iommu has a work around method to fix this but now
> > it doesn't. So we could fix this in gic code but maybe still need a fixes
> > tag here.
> >
> > Fixes: 05f80300dc8b ("iommu: Finish making iommu_group support mandatory")
> > Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
>
> That looks pretty horrible. Please see the patch I posted in response to
> your initial report:
>
> http://marc.info/?l=linux-pci&m=150295809430903&w=2

Aha, I saw it but I didn't get your point of "I'm not convinced  that
playing with the group refcount in an irqchip is the right approach..."

So, I'm not sure whether you prefer your patch?

> Thanks,
>
> 	M.