linux-kernel - Re: [PATCH v6 07/25] iommufd/access: Add internal APIs for HW queue to use

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Message-ID: <c3842cc4-f057-4ab6-b0bd-f7742ca7c645@linux.intel.com>
Date: Tue, 17 Jun 2025 12:23:20 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Nicolin Chen <nicolinc@...dia.com>, Jason Gunthorpe <jgg@...dia.com>
Cc: kevin.tian@...el.com, corbet@....net, will@...nel.org,
 bagasdotme@...il.com, robin.murphy@....com, joro@...tes.org,
 thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
 shuah@...nel.org, jsnitsel@...hat.com, nathan@...nel.org,
 peterz@...radead.org, yi.l.liu@...el.com, mshavit@...gle.com,
 praan@...gle.com, zhangzekun11@...wei.com, iommu@...ts.linux.dev,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
 linux-kselftest@...r.kernel.org, patches@...ts.linux.dev, mochs@...dia.com,
 alok.a.tiwari@...cle.com, vasant.hegde@....com, dwmw2@...radead.org
Subject: Re: [PATCH v6 07/25] iommufd/access: Add internal APIs for HW queue
 to use

On 6/17/25 10:25, Nicolin Chen wrote:
>>>   struct iommufd_eventq {
>>>   	struct iommufd_object obj;
>>>   	struct iommufd_ctx *ictx;
>>> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
>>> index 9293722b9cff..ad33f1e41a24 100644
>>> --- a/drivers/iommu/iommufd/device.c
>>> +++ b/drivers/iommu/iommufd/device.c
>>> @@ -1084,7 +1084,39 @@ void iommufd_access_destroy_object(struct iommufd_object *obj)
>>>   	if (access->ioas)
>>>   		WARN_ON(iommufd_access_change_ioas(access, NULL));
>>>   	mutex_unlock(&access->ioas_lock);
>>> -	iommufd_ctx_put(access->ictx);
>>> +	if (access->ops)
>>> +		iommufd_ctx_put(access->ictx);
>> I was hoping we could null the ictx to signal internal? That didn't
>> work out?
> access->ictx should be NULL for internal. It should have been:
> +	if (access->ictx)
> +		iommufd_ctx_put(access->ictx);

access->ictx could be treated as user ownership token. If it's NULL,
there is no user ownership, indicating it's owned by the kernel. This is
the concept here?

Thanks,
baolu