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

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Date:	Fri, 09 Aug 2013 14:58:49 +0900
From:	Cho KyongHo <pullip.cho@...sung.com>
To:	Tomasz Figa <t.figa@...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 Thu, 08 Aug 2013 16:00:18 +0200, Tomasz Figa wrote:
> 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;
> }
> 

Thank you for suggestion.
I think you are worrying about missing the information who makes 'ret' non-zero.
Ok. I will process it separately.

thanks

KyongHo.
> Best regards,
> Tomasz
> 
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