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    SubjectRe: [PATCH 08/10] xen/mmu: Bugfix. Fill the top entry page with appropriate middle layer pointers.
    On 12/21/2010 01:37 PM, Konrad Rzeszutek Wilk wrote:
    > If we swapped over from using an p2m_mid_identical to p2m_mid_missing
    > (earlier call to set_phys_to_machine) and then started going through the
    > PFNs in descending order to program a new MFN (balloon worker), we would
    > end up in this code path. At that point we would set up new page filled with
    > pointers to p2m_identity instead of p2m_missing. This had the disastrous
    > effect that get_phys_to_machine on that PFN would return an 1-1 mapping
    > instead of INVALID_P2M_ENTRY resulting in hitting a BUG check in balloon driver.
    >
    Are you going to fold this into the appropriate patch later?

    > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    > ---
    > arch/x86/xen/mmu.c | 5 ++++-
    > 1 files changed, 4 insertions(+), 1 deletions(-)
    >
    > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
    > index 92f4fec..a917439 100644
    > --- a/arch/x86/xen/mmu.c
    > +++ b/arch/x86/xen/mmu.c
    > @@ -480,7 +480,10 @@ static bool alloc_p2m(unsigned long pfn)
    > if (!mid)
    > return false;
    >
    > - p2m_mid_init(mid, p2m_identity);
    > + if (mid == p2m_mid_identity)
    > + p2m_mid_init(mid, p2m_identity);
    > + else
    > + p2m_mid_init(mid, p2m_missing);
    >
    > if (cmpxchg(top_p, mid_orig, mid) != mid_orig)
    > free_p2m_page(mid);



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