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Date:   Thu, 13 Oct 2022 17:51:33 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "hch@infradead.org" <hch@infradead.org>,
        "agordeev@linux.ibm.com" <agordeev@linux.ibm.com>,
        "wangkefeng.wang@huawei.com" <wangkefeng.wang@huawei.com>,
        "schnelle@linux.ibm.com" <schnelle@linux.ibm.com>,
        "David.Laight@ACULAB.COM" <David.Laight@aculab.com>,
        "shorne@gmail.com" <shorne@gmail.com>,
        Vineet Gupta <vgupta@kernel.org>,
        "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>
Subject: Re: [PATCH v3 05/11] arc: mm: Convert to GENERIC_IOREMAP
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References: <20221009103114.149036-1-bhe@redhat.com>
 <20221009103114.149036-6-bhe@redhat.com>
 <bbfa1fd5-3dae-2d00-0421-5f1e627eb8f7@csgroup.eu>
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On 10/12/22 at 10:17am, Christophe Leroy wrote:
......
> > -/*
> > - * ioremap with access flags
> > - * Cache semantics wise it is same as ioremap - "forced" uncached.
> > - * However unlike vanilla ioremap which bypasses ARC MMU for addresses in
> > - * ARC hardware uncached region, this one still goes thru the MMU as caller
> > - * might need finer access control (R/W/X)
> > - */
> > -void __iomem *ioremap_prot(phys_addr_t paddr, unsigned long size,
> > -			   unsigned long flags)
> > +void __iomem *
> > +arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val)
> >   {
> > -	unsigned int off;
> > -	unsigned long vaddr;
> > -	struct vm_struct *area;
> > -	phys_addr_t end;
> > -	pgprot_t prot = __pgprot(flags);
> > -
> > -	/* Don't allow wraparound, zero size */
> > -	end = paddr + size - 1;
> > -	if ((!size) || (end < paddr))
> > -		return NULL;
> > -
> >   	/* An early platform driver might end up here */
> >   	if (!slab_is_available())
> > -		return NULL;
> > +		return IOMEM_ERR_PTR(-EINVAL);
> 
> I think the slab_is_available() check should be done in the generic 
> functions. On all architectures SLAB must be available before you can 
> use get_vm_area_caller() and vunmap()

Tend to agree.

W/o slab initialized, the get_vm_area_caller() calling definitely will
fail. The arch's early ioremap code could call into this.