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    SubjectRe: [Xen-devel] [PATCH 1/3] x86: calculate precisely the memory needed by init_memory_mapping
    On Fri, 17 Jun 2011, Ian Jackson wrote:
    > stefano.stabellini@eu.citrix.com 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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