Re: [PATCH/RFC] driver core: Postpone DMA tear-down until after devres release

["Rafael J. Wysocki" <rafael@kernel.org>]

On Thu, Feb 7, 2019 at 8:42 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
>
> When unbinding the (IOMMU-enabled) R-Car SATA device on Salvator-XS
> (R-Car H3 ES2.0), in preparation of rebinding against vfio-platform for
> device pass-through for virtualization:
>
>     echo ee300000.sata > /sys/bus/platform/drivers/sata_rcar/unbind
>
> the kernel crashes with:
>
>     Unable to handle kernel paging request at virtual address ffffffbf029ffffc
>     Mem abort info:
>       ESR = 0x96000006
>       Exception class = DABT (current EL), IL = 32 bits
>       SET = 0, FnV = 0
>       EA = 0, S1PTW = 0
>     Data abort info:
>       ISV = 0, ISS = 0x00000006
>       CM = 0, WnR = 0
>     swapper pgtable: 4k pages, 39-bit VAs, pgdp = 000000007e8c586c
>     [ffffffbf029ffffc] pgd=000000073bfc6003, pud=000000073bfc6003, pmd=0000000000000000
>     Internal error: Oops: 96000006 [#1] SMP
>     Modules linked in:
>     CPU: 0 PID: 1098 Comm: bash Not tainted 5.0.0-rc5-salvator-x-00452-g37596f884f4318ef #287
>     Hardware name: Renesas Salvator-X 2nd version board based on r8a7795 ES2.0+ (DT)
>     pstate: 60400005 (nZCv daif +PAN -UAO)
>     pc : __free_pages+0x8/0x58
>     lr : __dma_direct_free_pages+0x50/0x5c
>     sp : ffffff801268baa0
>     x29: ffffff801268baa0 x28: 0000000000000000
>     x27: ffffffc6f9c60bf0 x26: ffffffc6f9c60bf0
>     x25: ffffffc6f9c60810 x24: 0000000000000000
>     x23: 00000000fffff000 x22: ffffff8012145000
>     x21: 0000000000000800 x20: ffffffbf029fffc8
>     x19: 0000000000000000 x18: ffffffc6f86c42c8
>     x17: 0000000000000000 x16: 0000000000000070
>     x15: 0000000000000003 x14: 0000000000000000
>     x13: ffffff801103d7f8 x12: 0000000000000028
>     x11: ffffff8011117604 x10: 0000000000009ad8
>     x9 : ffffff80110126d0 x8 : ffffffc6f7563000
>     x7 : 6b6b6b6b6b6b6b6b x6 : 0000000000000018
>     x5 : ffffff8011cf3cc8 x4 : 0000000000004000
>     x3 : 0000000000080000 x2 : 0000000000000001
>     x1 : 0000000000000000 x0 : ffffffbf029fffc8
>     Process bash (pid: 1098, stack limit = 0x00000000c38e3e32)
>     Call trace:
>      __free_pages+0x8/0x58
>      __dma_direct_free_pages+0x50/0x5c
>      arch_dma_free+0x1c/0x98
>      dma_direct_free+0x14/0x24
>      dma_free_attrs+0x9c/0xdc
>      dmam_release+0x18/0x20
>      release_nodes+0x25c/0x28c
>      devres_release_all+0x48/0x4c
>      device_release_driver_internal+0x184/0x1f0
>      device_release_driver+0x14/0x1c
>      unbind_store+0x70/0xb8
>      drv_attr_store+0x24/0x34
>      sysfs_kf_write+0x4c/0x64
>      kernfs_fop_write+0x154/0x1c4
>      __vfs_write+0x34/0x164
>      vfs_write+0xb4/0x16c
>      ksys_write+0x5c/0xbc
>      __arm64_sys_write+0x14/0x1c
>      el0_svc_common+0x98/0x114
>      el0_svc_handler+0x1c/0x24
>      el0_svc+0x8/0xc
>     Code: d51b4234 17fffffa a9bf7bfd 910003fd (b9403404)
>     ---[ end trace 8c564cdd3a1a840f ]---
>
> While I've bisected this to commit e8e683ae9a736407 ("iommu/of: Fix
> probe-deferral"), and reverting that commit on post-v5.0-rc4 kernels
> does fix the problem, this turned out to be a red herring.
>
> On arm64, arch_teardown_dma_ops() resets dev->dma_ops to NULL.
> Hence if a driver has used a managed DMA allocation API, the allocated
> DMA memory will be freed using the direct DMA ops, while it may have
> been allocated using a custom DMA ops (iommu_dma_ops in this case).
>
> Fix this by reversing the order of the calls to devres_release_all() and
> arch_teardown_dma_ops().
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
> Question:
> Is this safe on arm32, which calls arm_teardown_iommu_dma_ops() instead
> of resetting dev->dma_ops?
>
> ---
> Adding some debug code, and comparing before/after commit
> e8e683ae9a736407:
>
>      sata_rcar ee300000.sata: of_iommu_configure:227: err = -517
>     -sata_rcar ee300000.sata: of_iommu_configure:230: calling iommu_probe_device()
>     -sata_rcar ee300000.sata: iommu_probe_device:122: Calling ipmmu_add_device
>     -sata_rcar ee300000.sata: ipmmu_add_device:893
>     -sata_rcar ee300000.sata: of_iommu_configure:232: iommu_probe_device() returned -19
>     -sata_rcar ee300000.sata: dma_alloc_attrs:257: size 2048, ops =           (null)
>     -sata_rcar ee300000.sata: __dma_direct_alloc_pages:104: size 4096
>     -sata_rcar ee300000.sata: __dma_direct_alloc_pages:115: trying dma_alloc_from_contiguous()
>     -sata_rcar ee300000.sata: dma_alloc_from_contiguous:202: cma_alloc(1) returned page ffffffbf00d20e00
>     -sata_rcar ee300000.sata: dma_alloc_attrs:271: allocated using dma_direct_alloc()
>     -sata_rcar ee300000.sata: dmam_alloc_attrs:98: size 2048 vaddr ffffff8011e95000 dma_handle 0x0x000000007c040000 attrs 0x0
>     -scsi host0: sata_rcar
>     -ata1: SATA max UDMA/133 irq 172
>     -ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
>
> DMA memory used to be allocated from CMA, dma_map_ops = NULL.
> The SATA driver was probed and initialized.
>
>     +sata_rcar ee300000.sata: of_iommu_configure:234: skipping iommu_probe_device()
>
> SATA driver initialization is now deferred.
> Later, it is retried:
>
>     +sata_rcar ee300000.sata: of_iommu_configure:227: err = 0
>     +sata_rcar ee300000.sata: of_iommu_configure:230: calling iommu_probe_device()
>     +sata_rcar ee300000.sata: iommu_probe_device:122: Calling ipmmu_add_device
>     +sata_rcar ee300000.sata: ipmmu_add_device:893
>     +sata_rcar ee300000.sata: Using IPMMU context 1
>     +iommu: Adding device ee300000.sata to group 0
>     +sata_rcar ee300000.sata: ipmmu_add_device:908: Success
>     +sata_rcar ee300000.sata: of_iommu_configure:232: iommu_probe_device() returned 0
>     +sata_rcar ee300000.sata: dma_alloc_attrs:257: size 2048, ops = iommu_dma_ops
>     +sata_rcar ee300000.sata: dma_alloc_attrs:274: allocated using __iommu_alloc_attrs()
>     +sata_rcar ee300000.sata: dmam_alloc_attrs:98: size 2048 vaddr ffffff8012135000 dma_handle 0x0x00000000fffff000 attrs 0x0
>     +scsi host0: sata_rcar
>     +ata1: SATA max UDMA/133 irq 172
>     +ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
>
> DMA memory is now allocated using __iommu_alloc_attrs(), as dma_map_ops
> = iommu_dma_ops.
>
> Unbind:
>
>     -sata_rcar ee300000.sata: dmam_release:32: size 2048 vaddr ffffff8011e95000 dma_handle 0x0x000000007c040000 attrs 0x0
>     +sata_rcar ee300000.sata: dmam_release:32: size 2048 vaddr ffffff8012135000 dma_handle 0x0x00000000fffff000 attrs 0x0
>      sata_rcar ee300000.sata: dma_free_attrs:289: size 2048, ops =           (null)
>
> dma_map_ops = NULL, both before/after!
>
>      sata_rcar ee300000.sata: dma_free_attrs:308: calling dma_direct_free()
>     -sata_rcar ee300000.sata: __dma_direct_free_pages:189: size 2048 page ffffffbf00d20e00
>     -sata_rcar ee300000.sata: dma_release_from_contiguous:223: cma_release(1) freed
>     -sata_rcar ee300000.sata: __dma_direct_free_pages:194: skipping __free_pages()
>
> DMA memory was correctly freed using CMA.
>
>     +sata_rcar ee300000.sata: __dma_direct_free_pages:189: size 2048 page ffffffbf029fffc8
>     +sata_rcar ee300000.sata: dma_release_from_contiguous:225: cma_release(1) failed, cma area ffffff8011cf5530
>     +sata_rcar ee300000.sata: __dma_direct_free_pages:191: calling __free_pages()
>     +Unable to handle kernel paging request at virtual address ffffffbf029ffffc
>
> Memory is incorrectly freed using the direct ops, as dma_map_ops = NULL.
> Oops...
>
> After reversing the order of the calls to arch_teardown_dma_ops() and
> devres_release_all(), dma_map_ops is still valid, and the DMA memory is
> now released using __iommu_free_attrs():
>
>     +sata_rcar ee300000.sata: dmam_release:32: size 2048 vaddr ffffff8012145000 dma_handle 0x0x00000000fffff000 attrs 0x0
>     +sata_rcar ee300000.sata: dma_free_attrs:289: size 2048, ops = iommu_dma_ops
>     +sata_rcar ee300000.sata: dma_free_attrs:311: calling __iommu_free_attrs()
> ---
>  drivers/base/dd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 8ac10af17c0043a3..d62487d024559620 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -968,9 +968,9 @@ static void __device_release_driver(struct device *dev, struct device *parent)
>                         drv->remove(dev);
>
>                 device_links_driver_cleanup(dev);
> -               arch_teardown_dma_ops(dev);
>
>                 devres_release_all(dev);
> +               arch_teardown_dma_ops(dev);
>                 dev->driver = NULL;
>                 dev_set_drvdata(dev, NULL);
>                 if (dev->pm_domain && dev->pm_domain->dismiss)
> --
> 2.17.1
>

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