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xen-devel
Re: [Xen-devel] [PATCH 1/3] x86: calculate precisely the memory needed b
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To: |
Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] [PATCH 1/3] x86: calculate precisely the memory needed by init_memory_mapping |
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From: |
Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> |
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Date: |
Mon, 20 Jun 2011 20:16:01 +0100 |
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Cc: |
"xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "konrad.wilk@xxxxxxxxxx" <konrad.wilk@xxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, "hpa@xxxxxxxxx" <hpa@xxxxxxxxx>, "mingo@xxxxxxx" <mingo@xxxxxxx>, "hpa@xxxxxxxxxxxxxxx" <hpa@xxxxxxxxxxxxxxx>, "yinghai@xxxxxxxxxx" <yinghai@xxxxxxxxxx> |
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Mon, 20 Jun 2011 12:12:48 -0700 |
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<alpine.DEB.2.00.1106071849290.12963@kaball-desktop> <m2n.s.1QU0lc-137774@xxxxxxxxxxxxxxxxxxxxxx> <19963.35531.684825.285975@xxxxxxxxxxxxxxxxxxxxxxxx> |
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Alpine 2.00 (DEB 1167 2008-08-23) |
On Fri, 17 Jun 2011, Ian Jackson wrote:
> stefano.stabellini@xxxxxxxxxxxxx writes ("[Xen-devel] [PATCH 1/3] x86:
> calculate precisely the memory needed by init_memory_mapping"):
> > + if (pgt_buf_end != pgt_buf_top)
> > + printk(KERN_DEBUG "initial kernel pagetable allocation wasted
> > %lx"
> > + " pages\n", pgt_buf_top - pgt_buf_end);
>
> If (due to a bug) pgt_buf_end > pgt_buf_top, this will printk a
> message about wasting a negative number of pages, rather than
> crashing. Is there something else that will catch this case ?
Thanks for reviewing this patch!
Yes, there is something else that catches this case: both the 32 bit
and the 64 bit versions of alloc_low_page contain this code:
unsigned long pfn = pgt_buf_end++;
if (pfn >= pgt_buf_top)
panic("alloc_low_page: ran out of memory");
so we are safe from that point of view.
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