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authorJeremy Fitzhardinge <jeremy@goop.org>2009-01-28 14:35:02 -0800
committerH. Peter Anvin <hpa@linux.intel.com>2009-01-30 14:51:44 -0800
commit41edafdb78feac1d1f8823846209975fde990633 (patch)
tree00bb95195332962916be365c6119f17a22770758 /arch/x86/kernel/paravirt_patch_32.c
parent319f3ba52c71630865b10ac3b99dd020440d681d (diff)
x86/pvops: add a paravirt_ident functions to allow special patching
Impact: Optimization Several paravirt ops implementations simply return their arguments, the most obvious being the make_pte/pte_val class of operations on native. On 32-bit, the identity function is literally a no-op, as the calling convention uses the same registers for the first argument and return. On 64-bit, it can be implemented with a single "mov". This patch adds special identity functions for 32 and 64 bit argument, and machinery to recognize them and replace them with either nops or a mov as appropriate. At the moment, the only users for the identity functions are the pagetable entry conversion functions. The result is a measureable improvement on pagetable-heavy benchmarks (2-3%, reducing the pvops overhead from 5 to 2%). Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/kernel/paravirt_patch_32.c')
-rw-r--r--arch/x86/kernel/paravirt_patch_32.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c
index 9fe644f4861..d9f32e6d6ab 100644
--- a/arch/x86/kernel/paravirt_patch_32.c
+++ b/arch/x86/kernel/paravirt_patch_32.c
@@ -12,6 +12,18 @@ DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax");
DEF_NATIVE(pv_cpu_ops, clts, "clts");
DEF_NATIVE(pv_cpu_ops, read_tsc, "rdtsc");
+unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len)
+{
+ /* arg in %eax, return in %eax */
+ return 0;
+}
+
+unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len)
+{
+ /* arg in %edx:%eax, return in %edx:%eax */
+ return 0;
+}
+
unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
unsigned long addr, unsigned len)
{