linux-kernel - Re: [RFC PATCH v1 1/8] iommu/arm-smmu-v3: Add list of installed

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Message-ID: <ZN5vk9cVp0j0jd8T@nvidia.com>
Date:   Thu, 17 Aug 2023 16:05:55 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Michael Shavit <mshavit@...gle.com>
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, will@...nel.org, nicolinc@...dia.com,
        tina.zhang@...el.com, jean-philippe@...aro.org,
        robin.murphy@....com
Subject: Re: [RFC PATCH v1 1/8] iommu/arm-smmu-v3: Add list of installed_smmus

On Fri, Aug 18, 2023 at 02:16:23AM +0800, Michael Shavit wrote:
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index 83d2790b701e7..a9202d2045537 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -690,12 +690,20 @@ struct arm_smmu_stream {
>  	struct rb_node			node;
>  };
>  
> +/* List of smmu devices that a domain is installed to */
> +struct arm_smmu_installed_smmu {
> +	struct list_head	list;

'installed_smmus_item'

> +	/* List of masters that the domain is attached to*/
> +	struct list_head	devices;
> +	struct arm_smmu_device	*smmu;
> +};

Ah, if you have this struct you could just put

  u32 cache_tag; // ASID or VMID depending on domain type

And make both allocators local to the instance.

AFAIK the only specific thing that needs a global ASID is the SVA BTM
stuff and it already has code to handle collisions, it can just run
that code per-instance.

>  /* SMMU private data for each master */
>  struct arm_smmu_master {
>  	struct arm_smmu_device		*smmu;
>  	struct device			*dev;
>  	struct arm_smmu_domain		*domain;
> -	struct list_head		domain_head;
> +	struct list_head		list;

What is list for now?

Jason