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

From: Jason Gunthorpe <jgg@nvidia.com>
To: Michael Shavit <mshavit@google.com>
Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, will@kernel.org,
	nicolinc@nvidia.com, tina.zhang@intel.com,
	jean-philippe@linaro.org, robin.murphy@arm.com
Subject: Re: [RFC PATCH v1 1/8] iommu/arm-smmu-v3: Add list of installed_smmus
Date: Thu, 17 Aug 2023 16:05:55 -0300	[thread overview]
Message-ID: <ZN5vk9cVp0j0jd8T@nvidia.com> (raw)
In-Reply-To: <20230818021629.RFC.v1.1.I9df3dec9e33165276eba8e2dbf7025bfee286d90@changeid>

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