Re: [RFC PATCH v2 4/7] iommufd: Associate kvm pointer to iommufd ctx

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	Sean Christopherson <seanjc@google.com>
Cc: kvmarm@lists.linux.dev, iommu@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org, linuxarm@huawei.com,
	kevin.tian@intel.com, alex.williamson@redhat.com, maz@kernel.org,
	oliver.upton@linux.dev, will@kernel.org, robin.murphy@arm.com,
	jean-philippe@linaro.org, jonathan.cameron@huawei.com
Subject: Re: [RFC PATCH v2 4/7] iommufd: Associate kvm pointer to iommufd ctx
Date: Thu, 8 Feb 2024 11:42:10 -0400	[thread overview]
Message-ID: <20240208154210.GP31743@ziepe.ca> (raw)
In-Reply-To: <20240208151837.35068-5-shameerali.kolothum.thodi@huawei.com>

On Thu, Feb 08, 2024 at 03:18:34PM +0000, Shameer Kolothum wrote:

> diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> index 991f864d1f9b..28ede82bb1a6 100644
> --- a/drivers/iommu/iommufd/iommufd_private.h
> +++ b/drivers/iommu/iommufd/iommufd_private.h
> @@ -16,6 +16,7 @@ struct iommu_domain;
>  struct iommu_group;
>  struct iommu_option;
>  struct iommufd_device;
> +struct kvm;
>  
>  struct iommufd_ctx {
>  	struct file *file;
> @@ -27,6 +28,8 @@ struct iommufd_ctx {
>  	/* Compatibility with VFIO no iommu */
>  	u8 no_iommu_mode;
>  	struct iommufd_ioas *vfio_ioas;
> +	/* Associated KVM pointer */
> +	struct kvm *kvm;
>  };

Associating the KVM with the entire iommufd is a big hammer, is this
what we want to do?

I know it has to be linked to domain allocation and the coming
"viommu" object, and it is already linked to VFIO.

It means we support one KVM per iommufd (which doesn't seem
unreasonable, but also the first time we've had such a limitation)

The other option would be to pass in the kvm to the individual sub
objects.

Kevin?

Sean would you be OK with this approach considering your other series
to try to make more of this private?

Jason

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