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    SubjectRe: [PATCH] xen: convert p2m to a 3 level tree - partial revert
    On 01/27/2011 04:19 PM, Daniel Kiper wrote:
    > Hi,
    >
    > On Thu, Jan 27, 2011 at 04:02:31PM +0100, Stefan Bader wrote:
    >> On 01/27/2011 03:59 PM, Stefan Bader wrote:
    >>> On 01/27/2011 03:48 PM, Daniel Kiper wrote:
    >>>> Hi,
    >>>>
    >>>> Durning work on Xen memory hotplug I discoverd that
    >>>> 2.6.38-rc2 does not boot on domU. After some investigation
    >>>> it appeared that 58e05027b530ff081ecea68e38de8d59db8f87e0
    >>>> commit changed CONFIG_XEN_MAX_DOMAIN_MEMORY constant value
    >>>> to 128. This change does not allow to boot kernel on domU
    >>>> with small memory size (I could confirm that it is even
    >>>> not possible to boot kernel on domU with 2 GiB). Guest
    >>>> crash silently without any warning. Durning further
    >>>> research I found out that there is another commit published
    >>>> recently (8e1b4cf2108488ccfb9a3e7ed7cd85a435e01d4b) which attempts
    >>>> to fix this issue, however, it does not work on my platform.
    >>>> I decided to reenable CONFIG_XEN_MAX_DOMAIN_MEMORY option in
    >>>> kernel config and enable users to choose resonable values for
    >>>> their machines until better fix will be published. I think this
    >>>> solution is good because allow users to boot domU with newest
    >>>> kernel and allow developers to continue their work without
    >>>> time presure which could lead to new bugs.
    >>>
    >>> Have you tried with a version that contains
    >>>
    >>> commit 8e1b4cf2108488ccfb9a3e7ed7cd85a435e01d4b
    >>> Author: Stefan Bader <stefan.bader@canonical.com>
    >>> Date: Thu Jan 20 15:38:23 2011 +0100
    >>>
    >>> xen: p2m: correctly initialize partial p2m leaf
    >>>
    >>> I still may need to send a follow up to add a matching RESERVE_BRK, but at least
    >>> I was able to boot small DomU's again.
    >>>
    >>> -Stefan
    >>>> This patch applies cleanly to current Linus' kernel tree.
    >>
    >> Sorry, did not read careful enough. So you did. Maybe you could actually try to
    >> make the additional change of
    >>
    >> --- a/arch/x86/xen/p2m.c
    >> +++ b/arch/x86/xen/p2m.c
    >> @@ -61,6 +61,7 @@ static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_T
    >>
    >> RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PE
    >> RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MI
    >> +RESERVE_BRK(p2m_node, PAGE_SIZE);
    >>
    >> static inline unsigned p2m_top_index(unsigned long pfn)
    >> {
    >>
    >> This one I missed and probably that has more effects on big memory values.
    >
    > No, it does not work (CONFIG_XEN_MAX_DOMAIN_MEMORY=128).
    >

    Ok, thanks. So out of interest, what size of guest memory is failing for you?

    -Stefan

    > Daniel
    > --
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