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@xxxxxxxxx>
---
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@xxxxxxx>
---
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)
