From: Marc Gonzalez mgonzalez@freebox.fr
[ 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@freebox.fr Reviewed-by: Caleb Connolly caleb.connolly@linaro.org Reviewed-by: Bjorn Andersson andersson@kernel.org Link: https://lore.kernel.org/r/20240820-smmu-v3-1-2f71483b00ec@freebox.fr Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c index 36c6b36ad4ff7..b981ff25a983d 100644 --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c @@ -282,6 +282,13 @@ 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