This is a note to let you know that I've just added the patch titled
driver core: Postpone DMA tear-down until after devres release
to my driver-core git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git in the driver-core-testing branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will be merged to the driver-core-next branch sometime soon, after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
From c20bc458117bd45c1e4ada879947c5f046a4ea0c Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven geert+renesas@glider.be Date: Thu, 7 Feb 2019 20:36:53 +0100 Subject: driver core: Postpone DMA tear-down until after devres release MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
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 Acked-by: Christoph Hellwig hch@lst.de Reviewed-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 2e898cbba79b..348fc4695d4d 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -1058,9 +1058,9 @@ 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)