Re: [PATCH v2 0/2] iommu/arm-smmu-v3: make sure the kdump kernel can work well when smmu is enabled
From: Bhupesh Sharma
Date: Mon Apr 22 2019 - 08:33:48 EST
Hi Will,
On 04/16/2019 02:44 PM, Will Deacon wrote:
On Mon, Apr 08, 2019 at 10:31:47AM +0800, Leizhen (ThunderTown) wrote:
On 2019/4/4 23:30, Will Deacon wrote:
On Mon, Mar 18, 2019 at 09:12:41PM +0800, Zhen Lei wrote:
v1 --> v2:
1. Drop part2. Now, we only use the SMMUv3 hardware feature STE.config=0b000
(Report abort to device, no event recorded) to suppress the event messages
caused by the unexpected devices.
2. rewrite the patch description.
This issue came up a while back:
https://lore.kernel.org/linux-pci/20180302103032.GB19323@xxxxxxx/
and I'd still prefer to solve it using the disable_bypass logic which we
already have. Something along the lines of the diff below?
Yes, my patches also use disable_bypass=1(set ste.config=0b000). If
SMMU_IDR0.ST_LEVEL=0(Linear Stream table supported), then all STE entries
are allocated and initialized(set ste.config=0b000). But if SMMU_IDR0.ST_LEVEL=1
(2-level Stream Table), we only allocated and initialized the first level tables,
but leave level 2 tables dynamic allocated. That means, C_BAD_STREAMID(eventid=0x2)
will be reported, if an unexpeted device access memory without reinitialized in
kdump kernel.
So is your problem just that the C_BAD_STREAMID events are noisy? If so,
perhaps we should be disabling fault reporting entirely in the kdump kernel.
How about the update diff below? I'm keen to have this as simple as
possible, so we don't end up introducing rarely tested, complex code on
the crash path.
Will
--->8
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index d3880010c6cf..d8b73da6447d 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2454,13 +2454,9 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
/* Clear CR0 and sync (disables SMMU and queue processing) */
reg = readl_relaxed(smmu->base + ARM_SMMU_CR0);
if (reg & CR0_SMMUEN) {
- if (is_kdump_kernel()) {
- arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0);
- arm_smmu_device_disable(smmu);
- return -EBUSY;
- }
-
dev_warn(smmu->dev, "SMMU currently enabled! Resetting...\n");
+ WARN_ON(is_kdump_kernel() && !disable_bypass);
+ arm_smmu_update_gbpa(smmu, GBPA_ABORT, 0);
}
ret = arm_smmu_device_disable(smmu);
@@ -2553,6 +2549,8 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
return ret;
}
+ if (is_kdump_kernel())
+ enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
/* Enable the SMMU interface, or ensure bypass */
if (!bypass || disable_bypass) {
Thanks for the fix.
I can confirm that after this kdump kernel boots well for me on huawei
boards, so feel free to add:
Tested-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Here are the kdump kernel logs without this fix:
[ 4.514181] arm-smmu-v3 arm-smmu-v3.1.auto: EVTQ overflow detected --
events lost
.. And then repeating messages like the following ..
[ 4.521654] arm-smmu-v3 arm-smmu-v3.1.auto: event 0x02 received:
[ 4.527654] arm-smmu-v3 arm-smmu-v3.1.auto: 0x00007d0200000002
[ 4.533567] arm-smmu-v3 arm-smmu-v3.1.auto: 0x000000010000017e
[ 4.539478] arm-smmu-v3 arm-smmu-v3.1.auto: 0x00000000ff6de000
[ 4.545390] arm-smmu-v3 arm-smmu-v3.1.auto: 0x000000000eee03e8
And with the fix applied, kdump kernel logs can be seen below:
[ 9136.361094] Starting crashdump kernel...
[ 9136.365007] Bye!
[ 0.000000] Booting Linux on physical CPU 0x0000070002 [0x480fd010]
[ 0.000000] Linux version 5.1.0-rc6+
<..snip..>
[ 3.424103] arm-smmu-v3 arm-smmu-v3.0.auto: option mask 0x0
[ 3.429674] arm-smmu-v3 arm-smmu-v3.0.auto: ias 48-bit, oas 48-bit
(features 0x00000fef)
[ 3.437780] arm-smmu-v3 arm-smmu-v3.0.auto: SMMU currently enabled!
Resetting...
[ 3.445431] arm-smmu-v3 arm-smmu-v3.1.auto: option mask 0x0
<..snip..>
Thanks,
Bhupesh