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authorAvi Kivity <avi@redhat.com>2011-09-05 11:07:05 +0300
committerAnthony Liguori <aliguori@us.ibm.com>2011-09-09 12:58:16 -0500
commit36b586284e678da28df3af9fd0907d2b16f9311c (patch)
tree9aea538dac96f4481be4a7d3486b794546d21a72 /oslib-posix.c
parentdf00bed0fa30a6f5712456e7add783e470c534c9 (diff)
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qemu_vmalloc: align properly for transparent hugepages and KVM
To make good use of transparent hugepages, KVM requires that guest-physical and host-virtual addresses share the low 21 bits (as opposed to just the low 12 bits normally required). Adjust qemu_vmalloc() to honor that requirement. Ignore it for small regions to avoid fragmentation. Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'oslib-posix.c')
-rw-r--r--oslib-posix.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/oslib-posix.c b/oslib-posix.c
index 196099c..a304fb0 100644
--- a/oslib-posix.c
+++ b/oslib-posix.c
@@ -35,6 +35,13 @@
extern int daemon(int, int);
#endif
+#if defined(__linux__) && defined(__x86_64__)
+ /* Use 2MB alignment so transparent hugepages can be used by KVM */
+# define QEMU_VMALLOC_ALIGN (512 * 4096)
+#else
+# define QEMU_VMALLOC_ALIGN getpagesize()
+#endif
+
#include "config-host.h"
#include "sysemu.h"
#include "trace.h"
@@ -80,7 +87,12 @@ void *qemu_memalign(size_t alignment, size_t size)
void *qemu_vmalloc(size_t size)
{
void *ptr;
- ptr = qemu_memalign(getpagesize(), size);
+ size_t align = QEMU_VMALLOC_ALIGN;
+
+ if (size < align) {
+ align = getpagesize();
+ }
+ ptr = qemu_memalign(align, size);
trace_qemu_vmalloc(size, ptr);
return ptr;
}