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Message-ID: <347cfec9-f7d4-2fbd-b88a-ee6f4dc25a25@arm.com>
Date: Fri, 8 Feb 2019 11:34:37 +0000
From: Robin Murphy <robin.murphy@....com>
To: Geert Uytterhoeven <geert+renesas@...der.be>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Joerg Roedel <joro@...tes.org>,
"Rafael J . Wysocki" <rafael@...nel.org>
Cc: iommu@...ts.linux-foundation.org,
linux-arm-kernel@...ts.infradead.org,
linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC] driver core: Postpone DMA tear-down until after
devres release
On 07/02/2019 19:36, Geert Uytterhoeven 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@...der.be>
> ---
> Question:
> Is this safe on arm32, which calls arm_teardown_iommu_dma_ops() instead
> of resetting dev->dma_ops?
Should be - the principle is the same, and even if it did break that
would only be indicative of a separate bug being hidden by this one.
This fix looks entirely valid and correct to me:
Reviewed-by: Robin Murphy <robin.murphy@....com>
>
> ---
> 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)
>
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