From: "Jan Beulich" <jbeulich@novell.com>
To: Keir Fraser <keir.fraser@eu.citrix.com>,
Xiaowei Yang <xiaowei.yang@intel.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [PATCH] Fix domheap structure allocation when NUMA=on
Date: Fri, 20 Mar 2009 09:27:13 +0000 [thread overview]
Message-ID: <49C36F81.76E4.0078.0@novell.com> (raw)
In-Reply-To: <C5E90AB2.58CE%keir.fraser@eu.citrix.com>
>>> Keir Fraser <keir.fraser@eu.citrix.com> 20.03.09 09:56 >>>
>On 20/03/2009 08:47, "Jan Beulich" <jbeulich@novell.com> wrote:
>
>> virt_to_mfn(DIRECTMAP_VIRT_END - 1) is equal to
>>
>> Depending on whether DIRECTMAP_VIRT_END is the last byte or the first
>> following byte. Using "- 1" avoids such a dependency.
>>
>>> virt_to_mfn(DIRECTMAP_VIRT_END - PAGE_SIZE). Why +1? We use '<=' here.
>>
>> Because on the left side of the comparison we also calculate the first
>> following mfn, not the last included one.
>
>Since DIRECTMAP_VIRT_END is always the following byte not the last byte, it
>sounds like you think the page_alloc.c chunk is not needed at all. I'll just
>check in the header fix for now.
No, that chunk is necessary afaics - as I said I agree to Xiaowei's diagnosis
that virt_to_mfn() should not be used on DIRECTMAP_VIRT_END alone.
Subtracting 1 from it, and then adding back 1 to the result is indeed what
I think is the right thing to do here.
Jan
next prev parent reply other threads:[~2009-03-20 9:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-20 5:05 [PATCH] Fix domheap structure allocation when NUMA=on Yang, Xiaowei
2009-03-20 8:15 ` Jan Beulich
2009-03-20 8:34 ` Yang, Xiaowei
2009-03-20 8:47 ` Jan Beulich
2009-03-20 8:56 ` Keir Fraser
2009-03-20 9:27 ` Jan Beulich [this message]
2009-03-20 9:32 ` Keir Fraser
2009-03-24 10:48 ` Yang, Xiaowei
2009-03-24 10:55 ` Jan Beulich
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