One area where Xen deviates from Linux is that test_bit() forces a volatile
read. This leads to poor code generation, because the optimiser cannot merge
bit operations on the same word.
Drop the use of test_bit(), and write the expressions in regular C. This
removes the include of bitops.h (which is a frequent source of header
tangles), and it offers the optimiser far more flexibility.
Bloat-o-meter reports a net change of:
add/remove: 0/0 grow/shrink: 21/87 up/down: 641/-2751 (-2110)
with half of that in x86_emulate() alone. vmx_ctxt_switch_to() seems to be
the fastpath with the greatest delta at -24, where the optimiser has
successfully removed the branch hidden in cpu_has_msr_tsc_aux.
No functional change.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Wei Liu <w...@xen.org>
---
xen/arch/x86/include/asm/cpufeature.h | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/include/asm/cpufeature.h
b/xen/arch/x86/include/asm/cpufeature.h
index 4140ec0938b2..4f827cc6ff91 100644
--- a/xen/arch/x86/include/asm/cpufeature.h
+++ b/xen/arch/x86/include/asm/cpufeature.h
@@ -7,6 +7,7 @@
#define __ASM_I386_CPUFEATURE_H
#include <xen/const.h>
+#include <xen/stdbool.h>
#include <asm/cpuid.h>
#define cpufeat_word(idx) ((idx) / 32)
@@ -17,7 +18,6 @@
#define X86_FEATURE_ALWAYS X86_FEATURE_LM
#ifndef __ASSEMBLY__
-#include <xen/bitops.h>
struct cpuinfo_x86 {
unsigned char x86; /* CPU family */
@@ -43,8 +43,15 @@ struct cpuinfo_x86 {
extern struct cpuinfo_x86 boot_cpu_data;
-#define cpu_has(c, bit) test_bit(bit, (c)->x86_capability)
-#define boot_cpu_has(bit) test_bit(bit, boot_cpu_data.x86_capability)
+static inline bool cpu_has(const struct cpuinfo_x86 *info, unsigned int feat)
+{
+ return info->x86_capability[cpufeat_word(feat)] & cpufeat_mask(feat);
+}
+
+static inline bool boot_cpu_has(unsigned int feat)
+{
+ return cpu_has(&boot_cpu_data, feat);
+}
#define CPUID_PM_LEAF 6
#define CPUID6_ECX_APERFMPERF_CAPABILITY 0x1
base-commit: 8f9c8274a4e3e860bd777269cb2c91971e9fa69e
prerequisite-patch-id: ceeba7d5ab9498cb188e5012953c7e8c9a86347d
prerequisite-patch-id: c0957b9e1157ae6eb8de973c96716fd02587c486
prerequisite-patch-id: d2574bba15748cd021e5b33fa50e6cadc38863b6
prerequisite-patch-id: 0f66cd4287ffdc06f24dc01c7d26fb428f3e8c09
prerequisite-patch-id: a585f61b546ff96be3624ff253f8100b2f465de6
prerequisite-patch-id: 54551cdefaca083b4a4b97528d27d0f3dc9753ee
prerequisite-patch-id: 051423463e4a34728ab524f03e801e7103777684
--
2.30.2
