linux-kernel - Re: [patch 00/26] Xen-paravirt_ops: Xen guest implementation for paravirt

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Date:	Fri, 16 Mar 2007 12:26:27 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Christoph Hellwig <hch@...radead.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [patch 00/26] Xen-paravirt_ops: Xen guest implementation for
 paravirt_ops interface

Christoph Hellwig wrote:
> On Fri, Mar 16, 2007 at 10:26:55AM -0700, Jeremy Fitzhardinge wrote:
>   
>> +#ifdef CONFIG_HIGHPTE
>> +	.kmap_atomic_pte = native_kmap_atomic_pte,
>> +#else
>> +	.kmap_atomic_pte = paravirt_nop,
>> +#endif
>>     
>
> This is ifdefing is quite ugly.  Shouldn't native_kmap_atomic_pte
> just be a noop in the !CONFIG_HIGHPTE case?
>   

Yes, but the trouble is that asm/highmem.h simply isn't included in the
!HIGHMEM case, so I can't put anything in there, and putting anything
pv_ops related into linux/highmem.h isn't appropriate either.

>> -void *kmap_atomic(struct page *page, enum km_type type)
>> +void *_kmap_atomic(struct page *page, enum km_type type, pgprot_t prot)
>>     
>
> We normally call our "secial" function __foo, not _foo.  But in this
> case it really should have a more meaningfull name like
> kmap_atomic_prot anyway.
>   

OK.

>> +void *kmap_atomic(struct page *page, enum km_type type)
>> +{
>> +	return _kmap_atomic(page, type, kmap_prot);
>>     
>
> And this one should probably be an inline.
>   

OK, if you think it makes a difference.

>> +static inline void *native_kmap_atomic_pte(struct page *page, enum km_type type)
>> +{
>> +	return kmap_atomic(page, type);
>> +}
>> +
>> +#ifndef CONFIG_PARAVIRT
>> +#define kmap_atomic_pte(page, type)	kmap_atomic(page, type)
>> +#endif
>>     
>
> This is all getting rather ugly just for your pagetable hackery.
>   

Well, I could promote kmap_atomic_pte to a first-class interface, but it
seems like overkill.

    J
-
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