linux-kernel - Re: [Xen-devel] [PATCH 3/3] xen: use correct type for physical addresses

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Date:	Fri, 09 Jan 2015 12:56:59 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"David Vrabel" <david.vrabel@...rix.com>,
	"Juergen Gross" <JGross@...e.com>
Cc:	"xen-devel" <xen-devel@...ts.xenproject.org>,
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 3/3] xen: use correct type for physical
 addresses

>>> On 09.01.15 at 13:51, <david.vrabel@...rix.com> wrote:
> On 09/01/15 09:57, Jan Beulich wrote:
>>>>> On 08.01.15 at 18:01, <JGross@...e.com> wrote:
>>> @@ -284,7 +286,7 @@ static void __init xen_update_mem_tables(unsigned long pfn, unsigned long mfn)
>>>  	}
>>>  
>>>  	/* Update kernel mapping, but not for highmem. */
>>> -	if ((pfn << PAGE_SHIFT) >= __pa(high_memory))
>>> +	if (PFN_PHYS(pfn) >= (u64)(__pa(high_memory)))
>> 
>> I don't think you really need the cast on the right side - __pa()
>> should be returning a value of suitable type (and unsigned long
>> would be sufficient for anything up to and including high_memory).
> 
> I'd prefer:
> 
>     if (pfn >= PFN_DOWN(__pa(high_memory))

Even better indeed. Just one more point: Strictly speaking
__pa(high_memory) is invalid, as __pa() is defined for low
memory only. Hence perhaps PFN_UP(__pa(high_memory - 1))?

Jan

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