[dpdk-dev,1/2] eal/x86: use cpuid builtin
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Commit Message
Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>
---
lib/librte_eal/common/arch/x86/rte_cpuflags.c | 41 +++++----------------------
1 file changed, 7 insertions(+), 34 deletions(-)
Comments
Please could you explain why the asm code was used?
Are you sure this builtin is implemented everywhere?
On 23/08/2017 21:49, Thomas Monjalon wrote:
> Please could you explain why the asm code was used?
I guess we were not aware that there was a builtin for it.
> Are you sure this builtin is implemented everywhere?
>
Actually the builtin used in this patch is not supported in most CLANG
version (just recently merged upstream),
so I have reworked the patch to use builtin supported in both GCC and
CLANG 3.4+.
Thanks,
Sergio
@@ -36,6 +36,7 @@
#include <stdio.h>
#include <errno.h>
#include <stdint.h>
+#include <cpuid.h>
enum cpu_register_t {
RTE_REG_EAX = 0,
@@ -156,38 +157,12 @@ const struct feature_entry rte_cpu_feature_table[] = {
FEAT_DEF(INVTSC, 0x80000007, 0, RTE_REG_EDX, 8)
};
-/*
- * Execute CPUID instruction and get contents of a specific register
- *
- * This function, when compiled with GCC, will generate architecture-neutral
- * code, as per GCC manual.
- */
-static void
-rte_cpu_get_features(uint32_t leaf, uint32_t subleaf, cpuid_registers_t out)
-{
-#if defined(__i386__) && defined(__PIC__)
- /* %ebx is a forbidden register if we compile with -fPIC or -fPIE */
- asm volatile("movl %%ebx,%0 ; cpuid ; xchgl %%ebx,%0"
- : "=r" (out[RTE_REG_EBX]),
- "=a" (out[RTE_REG_EAX]),
- "=c" (out[RTE_REG_ECX]),
- "=d" (out[RTE_REG_EDX])
- : "a" (leaf), "c" (subleaf));
-#else
- asm volatile("cpuid"
- : "=a" (out[RTE_REG_EAX]),
- "=b" (out[RTE_REG_EBX]),
- "=c" (out[RTE_REG_ECX]),
- "=d" (out[RTE_REG_EDX])
- : "a" (leaf), "c" (subleaf));
-#endif
-}
-
int
rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
{
const struct feature_entry *feat;
cpuid_registers_t regs;
+ int ret;
if (feature >= RTE_CPUFLAG_NUMFLAGS)
/* Flag does not match anything in the feature tables */
@@ -199,13 +174,11 @@ rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
/* This entry in the table wasn't filled out! */
return -EFAULT;
- rte_cpu_get_features(feat->leaf & 0xffff0000, 0, regs);
- if (((regs[RTE_REG_EAX] ^ feat->leaf) & 0xffff0000) ||
- regs[RTE_REG_EAX] < feat->leaf)
- return 0;
-
- /* get the cpuid leaf containing the desired feature */
- rte_cpu_get_features(feat->leaf, feat->subleaf, regs);
+ ret = __get_cpuid_count(feat->leaf, feat->subleaf,
+ ®s[RTE_REG_EAX], ®s[RTE_REG_EBX],
+ ®s[RTE_REG_ECX], ®s[RTE_REG_EDX]);
+ if (!ret)
+ return ret;
/* check if the feature is enabled */
return (regs[feat->reg] >> feat->bit) & 1;