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From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	David Woodhouse <dwmw2@infradead.org>,
	iommu@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Jonathan Cameron <jic23@kernel.org>
Subject: Re: [PATCH v2 3/4] iommu/ioasid: Add custom allocators
Date: Wed, 2 Oct 2019 18:18:25 +0200
Message-ID: <20191002161825.GA626133@lophozonia> (raw)
In-Reply-To: <1569110870-12603-4-git-send-email-jacob.jun.pan@linux.intel.com>

Hi Jacob,

I have four tiny comments below but the patch looks great otherwise, no
major concern from me.

On Sat, Sep 21, 2019 at 05:07:49PM -0700, Jacob Pan wrote:
> +/*
> + * struct ioasid_allocator_data - Internal data structure to hold information
> + * about an allocator. There are two types of allocators:
> + *
> + * - Default allocator always has its own XArray to track the IOASIDs allocated.
> + * - Custom allocators may share allocation helpers with different private data.
> + *   Custom allocators that share the same helper functions also share the same
> + *   XArray.
> + * Rules:
> + * 1. Default allocator is always available, not dynamically registered. This is
> + *    to prevent race conditions with early boot code that want to register
> + *    custom allocators or allocate IOASIDs.
> + * 2. Custom allocators take precedence over the default allocator.
> + * 3. When all custom allocators sharing the same helper functions are
> + *    unregistered (e.g. due to hotplug), all outstanding IOASIDs must be
> + *    freed. Otherwise, outstand IOASIDs will be lost and orphaned.

                           outstanding

[...]
>  ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
>  		      void *private)
>  {
> -	ioasid_t id;
>  	struct ioasid_data *data;
> +	void *adata;
> +	ioasid_t id;

nit: changing the location of id could be in patch 2/4.

> -	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	data = kzalloc(sizeof(*data), GFP_ATOMIC);

I don't think that one needs to be GFP_ATOMIC. Otherwise it should
probably be done from the start, by patch 2/4.

>  	if (!data)
>  		return INVALID_IOASID;
>  
>  	data->set = set;
>  	data->private = private;
>  
> -	if (xa_alloc(&ioasid_xa, &id, data, XA_LIMIT(min, max), GFP_KERNEL)) {
> -		pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
> +	/*
> +	 * Custom allocator needs allocator data to perform platform specific
> +	 * operations.
> +	 */
> +	spin_lock(&ioasid_allocator_lock);
> +	adata = active_allocator->flags & IOASID_ALLOCATOR_CUSTOM ? active_allocator->ops->pdata : data;
> +	id = active_allocator->ops->alloc(min, max, adata);
> +	if (id == INVALID_IOASID) {
> +		pr_err("Failed ASID allocation %lu\n", active_allocator->flags);
> +		goto exit_free;
> +	}
> +
> +	if ((active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) &&
> +		xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id), GFP_ATOMIC)) {

nit: aligning at the "if (" would make this block more readable.

> +		/* Custom allocator needs framework to store and track allocation results */
> +		pr_err("Failed to alloc ioasid from %d\n", id);
> +		active_allocator->ops->free(id, active_allocator->ops->pdata);
>  		goto exit_free;
>  	}

Thanks,
Jean
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  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-22  0:07 [PATCH v2 0/4] User API for nested shared virtual address (SVA) Jacob Pan
2019-09-22  0:07 ` [PATCH v2 1/4] iommu: Introduce cache_invalidate API Jacob Pan
2019-09-22  0:07 ` [PATCH v2 2/4] iommu: Add I/O ASID allocator Jacob Pan
2019-09-22  1:45   ` kbuild test robot
2019-09-22  0:07 ` [PATCH v2 3/4] iommu/ioasid: Add custom allocators Jacob Pan
2019-10-02 16:18   ` Jean-Philippe Brucker [this message]
2019-10-02 17:20     ` Jacob Pan
2019-09-22  0:07 ` [PATCH v2 4/4] iommu: Introduce guest PASID bind function Jacob Pan

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