This is a note to let you know that I've just added the patch titled
iommu/arm-smmu-qcom: hide last LPASS SMMU context bank from linux
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
iommu-arm-smmu-qcom-hide-last-lpass-smmu-context-ban.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6ef42b7cf2e5d11181a58c20c0e3d5b9abd47c98
Author: Marc Gonzalez <mgonzalez@xxxxxxxxxx>
Date: Tue Aug 20 15:27:19 2024 +0200
iommu/arm-smmu-qcom: hide last LPASS SMMU context bank from linux
[ Upstream commit 3a8990b8a778219327c5f8ecf10b5d81377b925a ]
On qcom msm8998, writing to the last context bank of lpass_q6_smmu
(base address 0x05100000) produces a system freeze & reboot.
The hardware/hypervisor reports 13 context banks for the LPASS SMMU
on msm8998, but only the first 12 are accessible...
Override the number of context banks
[ 2.546101] arm-smmu 5100000.iommu: probing hardware configuration...
[ 2.552439] arm-smmu 5100000.iommu: SMMUv2 with:
[ 2.558945] arm-smmu 5100000.iommu: stage 1 translation
[ 2.563627] arm-smmu 5100000.iommu: address translation ops
[ 2.568923] arm-smmu 5100000.iommu: non-coherent table walk
[ 2.574566] arm-smmu 5100000.iommu: (IDR0.CTTW overridden by FW configuration)
[ 2.580220] arm-smmu 5100000.iommu: stream matching with 12 register groups
[ 2.587263] arm-smmu 5100000.iommu: 13 context banks (0 stage-2 only)
[ 2.614447] arm-smmu 5100000.iommu: Supported page sizes: 0x63315000
[ 2.621358] arm-smmu 5100000.iommu: Stage-1: 36-bit VA -> 36-bit IPA
[ 2.627772] arm-smmu 5100000.iommu: preserved 0 boot mappings
Specifically, the crashes occur here:
qsmmu->bypass_cbndx = smmu->num_context_banks - 1;
arm_smmu_cb_write(smmu, qsmmu->bypass_cbndx, ARM_SMMU_CB_SCTLR, 0);
and here:
arm_smmu_write_context_bank(smmu, i);
arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_FSR, ARM_SMMU_CB_FSR_FAULT);
It is likely that FW reserves the last context bank for its own use,
thus a simple work-around is: DON'T USE IT in Linux.
If we decrease the number of context banks, last one will be "hidden".
Signed-off-by: Marc Gonzalez <mgonzalez@xxxxxxxxxx>
Reviewed-by: Caleb Connolly <caleb.connolly@xxxxxxxxxx>
Reviewed-by: Bjorn Andersson <andersson@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240820-smmu-v3-1-2f71483b00ec@xxxxxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 272c9b35c9f0e..da249140ed2a1 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -254,6 +254,13 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
u32 smr;
int i;
+ /*
+ * MSM8998 LPASS SMMU reports 13 context banks, but accessing
+ * the last context bank crashes the system.
+ */
+ if (of_device_is_compatible(smmu->dev->of_node, "qcom,msm8998-smmu-v2") && smmu->num_context_banks == 13)
+ smmu->num_context_banks = 12;
+
/*
* Some platforms support more than the Arm SMMU architected maximum of
* 128 stream matching groups. For unknown reasons, the additional
