linux-kernel - Re: [PATCH 6/6] iommu/vt-d: Add domain_alloc

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Date:   Wed, 20 Sep 2023 13:28:41 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Yi Liu <yi.l.liu@...el.com>, joro@...tes.org,
        alex.williamson@...hat.com, jgg@...dia.com, kevin.tian@...el.com,
        robin.murphy@....com
Cc:     baolu.lu@...ux.intel.com, cohuck@...hat.com, eric.auger@...hat.com,
        nicolinc@...dia.com, kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.y.sun@...ux.intel.com,
        peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        zhenzhong.duan@...el.com, joao.m.martins@...cle.com
Subject: Re: [PATCH 6/6] iommu/vt-d: Add domain_alloc_user op

On 9/19/23 5:25 PM, Yi Liu wrote:
> This adds the domain_alloc_user op implementation. It supports allocating
> domains to be used as parent under nested translation.

Documentation/process/submitting-patches.rst:

Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
to do frotz", as if you are giving orders to the codebase to change
its behaviour.

So how about,

Add the domain_alloc_user callback to support allocating domains used as
parent under nested translation.

?

> 
> Signed-off-by: Yi Liu <yi.l.liu@...el.com>
> ---
>   drivers/iommu/intel/iommu.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 5db283c17e0d..491bcde1ff96 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4074,6 +4074,25 @@ static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
>   	return NULL;
>   }
>   
> +static struct iommu_domain *
> +intel_iommu_domain_alloc_user(struct device *dev, u32 flags)
> +{
> +	struct iommu_domain *domain;
> +	struct intel_iommu *iommu;
> +
> +	iommu = device_to_iommu(dev, NULL, NULL);
> +	if (!iommu)
> +		return ERR_PTR(-ENODEV);
> +
> +	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) && !ecap_nest(iommu->ecap))
> +		return ERR_PTR(-EOPNOTSUPP);
> +
> +	domain = iommu_domain_alloc(dev->bus);

No need to bounce between core and driver. Just,

	intel_iommu_domain_alloc(IOMMU_DOMAIN_UNMANAGED);

and fully initialize it before return.

> +	if (!domain)
> +		domain = ERR_PTR(-ENOMEM);
> +	return domain;
> +}
> +
>   static void intel_iommu_domain_free(struct iommu_domain *domain)
>   {
>   	if (domain != &si_domain->domain && domain != &blocking_domain)
> @@ -4807,6 +4826,7 @@ const struct iommu_ops intel_iommu_ops = {
>   	.capable		= intel_iommu_capable,
>   	.hw_info		= intel_iommu_hw_info,
>   	.domain_alloc		= intel_iommu_domain_alloc,
> +	.domain_alloc_user	= intel_iommu_domain_alloc_user,
>   	.probe_device		= intel_iommu_probe_device,
>   	.probe_finalize		= intel_iommu_probe_finalize,
>   	.release_device		= intel_iommu_release_device,

Best regards,
baolu