From 36b586284e678da28df3af9fd0907d2b16f9311c Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Mon, 5 Sep 2011 11:07:05 +0300 Subject: [PATCH] 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 Signed-off-by: Anthony Liguori --- oslib-posix.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/oslib-posix.c b/oslib-posix.c index 196099cc7..a304fb0f5 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; }