path: root/util/osdep.c
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authorMichael S. Tsirkin <>2015-12-02 21:14:12 +0200
committerMichael S. Tsirkin <>2015-12-02 22:38:23 +0200
commit7197fb4058bcb68986bae2bb2c04d6370f3e7218 (patch)
treec61e664c27278f8497fb9fec90cbb88383bf1d0e /util/osdep.c
parent0560b0e97df3da43651158c799c6d889f27529c3 (diff)
util/mmap-alloc: fix hugetlb support on ppc64
Since commit 8561c9244ddf1122d "exec: allocate PROT_NONE pages on top of RAM", it is no longer possible to back guest RAM with hugepages on ppc64 hosts: mmap(NULL, 285212672, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x3fff57000000 mmap(0x3fff57000000, 268435456, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 19, 0) = -1 EBUSY (Device or resource busy) This is because on ppc64, Linux fixes a page size for a virtual address at mmap time, so we can't switch a range of memory from anonymous small pages to hugetlbs with MAP_FIXED. See commit d0f13e3c20b6fb73ccb467bdca97fa7cf5a574cd ("[POWERPC] Introduce address space "slices"") in Linux history for the details. Detect this and create the PROT_NONE mapping using the same fd. Naturally, this makes the guard page bigger with hugetlbfs. Based on patch by Greg Kurz. Acked-by: Rik van Riel <> Reviewed-by: Greg Kurz <> Tested-by: Greg Kurz <> Signed-off-by: Michael S. Tsirkin <>
Diffstat (limited to 'util/osdep.c')
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