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Re: [Xen-devel] Xen 4.3 + tmem = Xen BUG at domain_page.c:143

The BUG_ON() here is definitely valid - a few lines down, after the
enclosing if(), we use it in ways that requires this to not have
triggered. It basically tells you whether an in range idx was found,
which apparently isn't the case here.

As I think George already pointed out - printing accum here would
be quite useful: It should have at least one of the low 32 bits set,
given that dcache->entries must be at most 32 according to the
data you already got logged.

With extra debugging (see attached patch)

(XEN) domain_page.c:125:d1 mfn: 1eb483, [0]: bffff1ff, ~ffffffff40000e00, idx: 9 garbage: 40000e00, inuse: ffffffff (XEN) domain_page.c:125:d1 mfn: 1eb480, [0]: fdbfffff, ~ffffffff02400000, idx: 22 garbage: 2400000, inuse: ffffffff (XEN) domain_page.c:125:d1 mfn: 2067ca, [0]: fffff7ff, ~ffffffff00000800, idx: 11 garbage: 800, inuse: ffffffff (XEN) domain_page.c:125:d1 mfn: 183642, [0]: ffffffff, ~ffffffff00000000, idx: 32 garbage: 0, inuse: ffffffff (XEN) domain_page.c:170:d1 mfn (183642) -> 2 idx: 32(i:1,j:0), branch:9 0xffffffff00000000
(XEN) domain_page.c:176:d1 [0] idx=13, mfn=0x203b00, refcnt: 0
(XEN) domain_page.c:176:d1 [1] idx=25, mfn=0x1839e1, refcnt: 0
(XEN) domain_page.c:176:d1 [2] idx=3, mfn=0x1824d2, refcnt: 0
(XEN) domain_page.c:176:d1 [3] idx=5, mfn=0x1eb48b, refcnt: 0
(XEN) domain_page.c:176:d1 [4] idx=28, mfn=0x203b04, refcnt: 0
(XEN) domain_page.c:176:d1 [5] idx=0, mfn=0x1eb485, refcnt: 0
(XEN) domain_page.c:176:d1 [6] idx=30, mfn=0x203afe, refcnt: 0
(XEN) domain_page.c:176:d1 [7] idx=20, mfn=0x203aff, refcnt: 0

And that does point the picture that we have exhausted the full 32 entries of mapcache.

Now off to find out who is holding them and why. Aren't these operations (map/unmap domain_page) suppose to be shortlived?

Attachment: xen-domain_page-v3.patch
Description: Text Data

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