linux-kernel - Re: [PATCH v9 04/16] iommu/exynos: allocate lv2 page table from own slab

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Date:	Thu, 08 Aug 2013 16:00:18 +0200
From:	Tomasz Figa <t.figa@...sung.com>
To:	Cho KyongHo <pullip.cho@...sung.com>
Cc:	'Linux ARM Kernel' <linux-arm-kernel@...ts.infradead.org>,
	'Linux IOMMU' <iommu@...ts.linux-foundation.org>,
	'Linux Kernel' <linux-kernel@...r.kernel.org>,
	'Linux Samsung SOC' <linux-samsung-soc@...r.kernel.org>,
	devicetree@...r.kernel.org, 'Joerg Roedel' <joro@...tes.org>,
	'Kukjin Kim' <kgene.kim@...sung.com>,
	'Prathyush' <prathyush.k@...sung.com>,
	'Rahul Sharma' <rahul.sharma@...sung.com>,
	'Subash Patel' <supash.ramaswamy@...aro.org>,
	'Grant Grundler' <grundler@...omium.org>,
	'Antonios Motakis' <a.motakis@...tualopensystems.com>,
	kvmarm@...ts.cs.columbia.edu,
	'Sachin Kamat' <sachin.kamat@...aro.org>
Subject: Re: [PATCH v9 04/16] iommu/exynos: allocate lv2 page table from own
 slab

On Thursday 08 of August 2013 18:38:04 Cho KyongHo wrote:
> Since kmalloc() does not guarantee that the allignment of 1KiB when it
> allocates 1KiB, it is required to allocate lv2 page table from own
> slab that guarantees alignment of 1KiB
> 
> Signed-off-by: Cho KyongHo <pullip.cho@...sung.com>
> ---
>  drivers/iommu/exynos-iommu.c |   24 ++++++++++++++++++++----
>  1 files changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> index d90e6fa..a318049 100644
> --- a/drivers/iommu/exynos-iommu.c
> +++ b/drivers/iommu/exynos-iommu.c
> @@ -100,6 +100,8 @@
>  #define REG_PB1_SADDR		0x054
>  #define REG_PB1_EADDR		0x058
> 
> +static struct kmem_cache *lv2table_kmem_cache;
> +
>  static unsigned long *section_entry(unsigned long *pgtable, unsigned
> long iova) {
>  	return pgtable + lv1ent_offset(iova);
> @@ -765,7 +767,8 @@ static void exynos_iommu_domain_destroy(struct
> iommu_domain *domain)
> 
>  	for (i = 0; i < NUM_LV1ENTRIES; i++)
>  		if (lv1ent_page(priv->pgtable + i))
> -			kfree(__va(lv2table_base(priv->pgtable + i)));
> +			kmem_cache_free(lv2table_kmem_cache,
> +					__va(lv2table_base(priv->pgtable + i)));
> 
>  	free_pages((unsigned long)priv->pgtable, 2);
>  	free_pages((unsigned long)priv->lv2entcnt, 1);
> @@ -861,7 +864,7 @@ static unsigned long *alloc_lv2entry(unsigned long
> *sent, unsigned long iova, if (lv1ent_fault(sent)) {
>  		unsigned long *pent;
> 
> -		pent = kzalloc(LV2TABLE_SIZE, GFP_ATOMIC);
> +		pent = kmem_cache_zalloc(lv2table_kmem_cache, GFP_ATOMIC);
>  		BUG_ON((unsigned long)pent & (LV2TABLE_SIZE - 1));
>  		if (!pent)
>  			return ERR_PTR(-ENOMEM);
> @@ -881,7 +884,7 @@ static int lv1set_section(unsigned long *sent,
> phys_addr_t paddr, short *pgcnt)
> 
>  	if (lv1ent_page(sent)) {
>  		BUG_ON(*pgcnt != NUM_LV2ENTRIES);
> -		kfree(page_entry(sent, 0));
> +		kmem_cache_free(lv2table_kmem_cache, page_entry(sent, 0));
>  		*pgcnt = 0;
>  	}
> 
> @@ -1082,10 +1085,23 @@ static int __init exynos_iommu_init(void)
>  {
>  	int ret;
> 
> +	lv2table_kmem_cache = kmem_cache_create("exynos-iommu-lv2table",
> +				LV2TABLE_SIZE, LV2TABLE_SIZE, 0, NULL);
> +	if (!lv2table_kmem_cache) {
> +		pr_err("%s: Failed to create kmem cache\n", __func__);
> +		return -ENOMEM;
> +	}
> +
>  	ret = platform_driver_register(&exynos_sysmmu_driver);
> 
>  	if (ret == 0)
> -		bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
> +		ret = bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
> +
> +	if (ret) {
> +		pr_err("%s: Failed to register exynos-iommu driver.\n",
> +								__func__);
> +		kmem_cache_destroy(lv2table_kmem_cache);
> +	}

What about making the return value handling here cleaner? For example:

	lv2table_kmem_cache = kmem_cache_create("exynos-iommu-lv2table",
				LV2TABLE_SIZE, LV2TABLE_SIZE, 0, NULL);
	if (!lv2table_kmem_cache) {
		...
		return -ENOMEM;
	}

	ret = platform_driver_register(&exynos_sysmmu_driver);
	if (ret) {
		...
		goto err_destroy_kmem_cache;
	}

	ret = bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
	if (ret) {
		...
		goto err_platform_unregister;
	}

	return 0;

err_platform_unregister:
	...
err_destroy_kmem_cache:
	...
	return ret;
}

Best regards,
Tomasz

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