Re: [RESEND][PATCH 1/2] arm-smmu-qcom: Ensure the qcom_scm driver has finished probing

2020-11-13 Thread Robin Murphy 

On 2020-11-12 22:05, John Stultz wrote:

Robin Murphy pointed out that if the arm-smmu driver probes before
the qcom_scm driver, we may call qcom_scm_qsmmu500_wait_safe_toggle()
before the __scm is initialized.

Now, getting this to happen is a bit contrived, as in my efforts it
required enabling asynchronous probing for both drivers, moving the
firmware dts node to the end of the dtsi file, as well as forcing a
long delay in the qcom_scm_probe function.

With those tweaks we ran into the following crash:
[2.631040] arm-smmu 1500.iommu: Stage-1: 48-bit VA -> 48-bit IPA
[2.633372] Unable to handle kernel NULL pointer dereference at virtual 
address 
...
[2.633402] [] user address but active_mm is swapper
[2.633409] Internal error: Oops: 9605 [#1] PREEMPT SMP
[2.633415] Modules linked in:
[2.633427] CPU: 5 PID: 117 Comm: kworker/u16:2 Tainted: GW 
5.10.0-rc1-mainline-00025-g272a618fc36-dirty #3971
[2.633430] Hardware name: Thundercomm Dragonboard 845c (DT)
[2.633448] Workqueue: events_unbound async_run_entry_fn
[2.633456] pstate: 80c5 (Nzcv daif +PAN +UAO -TCO BTYPE=--)
[2.633465] pc : qcom_scm_qsmmu500_wait_safe_toggle+0x78/0xb0
[2.633473] lr : qcom_smmu500_reset+0x58/0x78
[2.633476] sp : ffc0105a3b60
...
[2.633567] Call trace:
[2.633572]  qcom_scm_qsmmu500_wait_safe_toggle+0x78/0xb0
[2.633576]  qcom_smmu500_reset+0x58/0x78
[2.633581]  arm_smmu_device_reset+0x194/0x270
[2.633585]  arm_smmu_device_probe+0xc94/0xeb8
[2.633592]  platform_drv_probe+0x58/0xa8
[2.633597]  really_probe+0xec/0x398
[2.633601]  driver_probe_device+0x5c/0xb8
[2.633606]  __driver_attach_async_helper+0x64/0x88
[2.633610]  async_run_entry_fn+0x4c/0x118
[2.633617]  process_one_work+0x20c/0x4b0
[2.633621]  worker_thread+0x48/0x460
[2.633628]  kthread+0x14c/0x158
[2.633634]  ret_from_fork+0x10/0x18
[2.633642] Code: a9034fa0 d0007f73 29107fa0 91342273 (f9400020)

To avoid this, this patch adds a check on qcom_scm_is_available() in
the qcom_smmu_impl_init() function, returning -EPROBE_DEFER if its
not ready.

This allows the driver to try to probe again later after qcom_scm has
finished probing.


As well as strict correctness, the other motivation here was that 
qcom_scm_is_available() should be the place to add the "is the module 
even loaded yet?" dance to iron out the awkward config dependencies in 
future.


Reviewed-by: Robin Murphy 


Cc: Robin Murphy 
Cc: Will Deacon 
Cc: Andy Gross 
Cc: Maulik Shah 
Cc: Bjorn Andersson 
Cc: Saravana Kannan 
Cc: Marc Zyngier 
Cc: Lina Iyer 
Cc: iommu@lists.linux-foundation.org
Cc: linux-arm-msm 
Reported-by: Robin Murphy 
Signed-off-by: John Stultz 
---
  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 4 
  1 file changed, 4 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c 
b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 66ba4870659f4..ef37ccfa82562 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -159,6 +159,10 @@ struct arm_smmu_device *qcom_smmu_impl_init(struct 
arm_smmu_device *smmu)
  {
struct qcom_smmu *qsmmu;
  
+	/* Check to make sure qcom_scm has finished probing */

+   if (!qcom_scm_is_available())
+   return ERR_PTR(-EPROBE_DEFER);
+
qsmmu = devm_kzalloc(smmu->dev, sizeof(*qsmmu), GFP_KERNEL);
if (!qsmmu)
return ERR_PTR(-ENOMEM);


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[RESEND][PATCH 1/2] arm-smmu-qcom: Ensure the qcom_scm driver has finished probing

2020-11-12 Thread John Stultz 
Robin Murphy pointed out that if the arm-smmu driver probes before
the qcom_scm driver, we may call qcom_scm_qsmmu500_wait_safe_toggle()
before the __scm is initialized.

Now, getting this to happen is a bit contrived, as in my efforts it
required enabling asynchronous probing for both drivers, moving the
firmware dts node to the end of the dtsi file, as well as forcing a
long delay in the qcom_scm_probe function.

With those tweaks we ran into the following crash:
[2.631040] arm-smmu 1500.iommu: Stage-1: 48-bit VA -> 48-bit IPA
[2.633372] Unable to handle kernel NULL pointer dereference at virtual 
address 
...
[2.633402] [] user address but active_mm is swapper
[2.633409] Internal error: Oops: 9605 [#1] PREEMPT SMP
[2.633415] Modules linked in:
[2.633427] CPU: 5 PID: 117 Comm: kworker/u16:2 Tainted: GW 
5.10.0-rc1-mainline-00025-g272a618fc36-dirty #3971
[2.633430] Hardware name: Thundercomm Dragonboard 845c (DT)
[2.633448] Workqueue: events_unbound async_run_entry_fn
[2.633456] pstate: 80c5 (Nzcv daif +PAN +UAO -TCO BTYPE=--)
[2.633465] pc : qcom_scm_qsmmu500_wait_safe_toggle+0x78/0xb0
[2.633473] lr : qcom_smmu500_reset+0x58/0x78
[2.633476] sp : ffc0105a3b60
...
[2.633567] Call trace:
[2.633572]  qcom_scm_qsmmu500_wait_safe_toggle+0x78/0xb0
[2.633576]  qcom_smmu500_reset+0x58/0x78
[2.633581]  arm_smmu_device_reset+0x194/0x270
[2.633585]  arm_smmu_device_probe+0xc94/0xeb8
[2.633592]  platform_drv_probe+0x58/0xa8
[2.633597]  really_probe+0xec/0x398
[2.633601]  driver_probe_device+0x5c/0xb8
[2.633606]  __driver_attach_async_helper+0x64/0x88
[2.633610]  async_run_entry_fn+0x4c/0x118
[2.633617]  process_one_work+0x20c/0x4b0
[2.633621]  worker_thread+0x48/0x460
[2.633628]  kthread+0x14c/0x158
[2.633634]  ret_from_fork+0x10/0x18
[2.633642] Code: a9034fa0 d0007f73 29107fa0 91342273 (f9400020)

To avoid this, this patch adds a check on qcom_scm_is_available() in
the qcom_smmu_impl_init() function, returning -EPROBE_DEFER if its
not ready.

This allows the driver to try to probe again later after qcom_scm has
finished probing.

Cc: Robin Murphy 
Cc: Will Deacon 
Cc: Andy Gross 
Cc: Maulik Shah 
Cc: Bjorn Andersson 
Cc: Saravana Kannan 
Cc: Marc Zyngier 
Cc: Lina Iyer 
Cc: iommu@lists.linux-foundation.org
Cc: linux-arm-msm 
Reported-by: Robin Murphy 
Signed-off-by: John Stultz 
---
 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 4 
 1 file changed, 4 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c 
b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 66ba4870659f4..ef37ccfa82562 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -159,6 +159,10 @@ struct arm_smmu_device *qcom_smmu_impl_init(struct 
arm_smmu_device *smmu)
 {
struct qcom_smmu *qsmmu;
 
+   /* Check to make sure qcom_scm has finished probing */
+   if (!qcom_scm_is_available())
+   return ERR_PTR(-EPROBE_DEFER);
+
qsmmu = devm_kzalloc(smmu->dev, sizeof(*qsmmu), GFP_KERNEL);
if (!qsmmu)
return ERR_PTR(-ENOMEM);
-- 
2.17.1

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