linux-kernel - Re: [Bisected] [commit 2ad56efa80dba89162106c06ebc00b611325e584] [linux-next] WARNING while booting to kernel 6.6.0-rc3-next-20230929

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Date:   Wed, 4 Oct 2023 19:41:28 +0530
From:   Tasmiya Nalatwad <tasmiya@...ux.vnet.ibm.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     linux-kernel@...r.kernel.org, linux-next@...r.kernel.org,
        baolu.lu@...ux.intel.com, jsnitsel@...hat.com, jroedel@...e.de,
        mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
        gregkh@...uxfoundation.org, gbatra@...ux.vnet.ibm.com,
        ruscur@...sell.cc, linuxppc-dev@...ts.ozlabs.org,
        abdhalee@...ux.vnet.ibm.com, mputtash@...ux.vnet.com,
        sachinp@...ux.vnet.com
Subject: Re: [Bisected] [commit 2ad56efa80dba89162106c06ebc00b611325e584]
 [linux-next] WARNING while booting to kernel 6.6.0-rc3-next-20230929

Thanks Jason. Yes the suggested changes works and Warnings are not seen.

On 10/4/23 17:08, Jason Gunthorpe wrote:
> On Wed, Oct 04, 2023 at 04:37:10PM +0530, Tasmiya Nalatwad wrote:
>>     Greetings,
>>
>>     [linux-next] [6.6.0-rc3-next-20230929] [git bisect ->
>>     2ad56efa80dba89162106c06ebc00b611325e584]WARNING: CPU: 0 PID: 8 at
>>     arch/powerpc/kernel/[1]iommu.c:407 __iommu_free+0x1e4/0x1f0
>>     gitbisect is pointing to the below commit
>>     commit 2ad56efa80dba89162106c06ebc00b611325e584
>>         powerpc/iommu: Setup a default domain and remove set_platform_dma_ops
> I assume this means there are still sequencing problems with power at
> boot time. eg we turned on the dma ops in the wrong order or something
> like that
>
> As far as I can see the only difference here is that we do the
> operation to claim dma ops during the iommu drive probe. We can avoid that.
>
> Does this work for you?
>
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index d6ad3fde85a212..115b9031badac7 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -1280,13 +1280,19 @@ struct iommu_table_group_ops spapr_tce_table_group_ops = {
>   /*
>    * A simple iommu_ops to allow less cruft in generic VFIO code.
>    */
> -static int spapr_tce_platform_iommu_attach_dev(struct iommu_domain *dom,
> -					       struct device *dev)
> +static int
> +spapr_tce_platform_iommu_attach_dev(struct iommu_domain *platform_domain,
> +				    struct device *dev)
>   {
> +	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
>   	struct iommu_group *grp = iommu_group_get(dev);
>   	struct iommu_table_group *table_group;
>   	int ret = -EINVAL;
>
> +	/* At first attach the ownership is already set */
> +	if (!domain)
> +		return 0;
> +
>   	if (!grp)
>   		return -ENODEV;
>
>
-- 
Regards,
Tasmiya Nalatwad
IBM Linux Technology Center