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Message-ID: <2101296.S6JDU5igl3@flatron>
Date: Fri, 09 Aug 2013 09:55:30 +0200
From: Tomasz Figa <tomasz.figa@...il.com>
To: Cho KyongHo <pullip.cho@...sung.com>
Cc: Tomasz Figa <t.figa@...sung.com>,
'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
Hi KyongHo,
On Friday 09 of August 2013 14:58:49 Cho KyongHo wrote:
> 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.
Oh, this is a valid point, but it was more a nitpick about the coding
style. Single path error handling (with goto) is widely used in the kernel
in cases when more than one thing has to be undone and so I suggested this
method of error handling here as well.
> Ok. I will process it separately.
Since this patch adds most of the error handling to this function, I think
it should be fine to do it as a part of this patch.
Best regards,
Tomasz
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