ACK: [PATCH][Unstable][SRU Disco] iommu/arm-smmu-v3: Don't disable SMMU in kdump kernel

Stefan Bader stefan.bader at canonical.com
Wed May 29 14:11:00 UTC 2019


On 13.05.19 20:28, dann frazier wrote:
> From: Will Deacon <will.deacon at arm.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1828868
> 
> Disabling the SMMU when probing from within a kdump kernel so that all
> incoming transactions are terminated can prevent the core of the crashed
> kernel from being transferred off the machine if all I/O devices are
> behind the SMMU.
> 
> Instead, continue to probe the SMMU after it is disabled so that we can
> reinitialise it entirely and re-attach the DMA masters as they are reset.
> Since the kdump kernel may not have drivers for all of the active DMA
> masters, we suppress fault reporting to avoid spamming the console and
> swamping the IRQ threads.
> 
> Reported-by: "Leizhen (ThunderTown)" <thunder.leizhen at huawei.com>
> Tested-by: "Leizhen (ThunderTown)" <thunder.leizhen at huawei.com>
> Tested-by: Bhupesh Sharma <bhsharma at redhat.com>
> Signed-off-by: Will Deacon <will.deacon at arm.com>
> (cherry picked from commit 3f54c447df34ff9efac7809a4a80fd3208efc619)
> Signed-off-by: dann frazier <dann.frazier at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  drivers/iommu/arm-smmu-v3.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 0d284029dc735..e6baf509bc07d 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2455,13 +2455,9 @@ 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);
> @@ -2554,6 +2550,8 @@ 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) {
> 


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