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xen/mmu: WARN_ON when racing to swap middle leaf.

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The initial bootup code uses set_phys_to_machine quite a lot, and after
bootup it would be used by the balloon driver. The balloon driver does have
mutex lock so this should not be necessary - but just in case, add
a WARN_ON if we do hit this scenario. If we do fail this, it is OK
to continue as there is a backup mechanism (VM_IO) that can bypass
the P2M and still set the _PAGE_IOMAP flags.

[v2: Change from WARN to BUG_ON]
[v3: Rebased on top of xen->p2m code split]
[v4: Change from BUG_ON to WARN]
Reviewed-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2011-01-18 20:17:10 -05:00
parent fb38923ead
commit c761779877
1 changed files with 2 additions and 1 deletions
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3
arch/x86/xen/p2m.c
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@ -605,7 +605,8 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
/* Swap over from MISSING to IDENTITY if needed. */
if (p2m_top[topidx][mididx] == p2m_missing) {
p2m_top[topidx][mididx] = p2m_identity;
WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
p2m_identity) != p2m_missing);
return true;
}
}