The driver crc32c-intel match CPUs supporting X86_FEATURE_XMM4_2.
On platforms with Zhaoxin CPUs supporting this X86 feature, when
crc32c-intel and crc32c-generic are both registered, system will
use crc32c-intel because its .cra_priority is greater than
crc32c-generic.
When doing lmbench3 Create and Delete file test on partitions with
ext4 enabling metadata checksum, found using crc32c-generic driver
could get about 20% performance gain than using the driver crc32c-intel
on some Zhaoxin CPUs.
This case expect to use crc32c-generic driver for these Zhaoxin CPUs
to get performance gain, so remove these Zhaoxin CPUs support from
crc32c-intel.
Signed-off-by: Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx>
---
arch/x86/crypto/crc32c-intel_glue.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/arch/x86/crypto/crc32c-intel_glue.c b/arch/x86/crypto/crc32c-intel_glue.c
index feccb52..5171091 100644
--- a/arch/x86/crypto/crc32c-intel_glue.c
+++ b/arch/x86/crypto/crc32c-intel_glue.c
@@ -215,14 +215,31 @@ static struct shash_alg alg = {
};
static const struct x86_cpu_id crc32c_cpu_id[] = {
- X86_MATCH_FEATURE(X86_FEATURE_XMM4_2, NULL),
+ /*
+ * Negative entries; exclude these chips from using this driver.
+ * They match the positive rule below, but their CRC32 instruction
+ * implementation is so slow, it doesn't merit use.
+ */
+ X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 0x6, X86_FEATURE_XMM4_2, false),
+ X86_MATCH_VENDOR_FAM_MODEL_FEATURE(ZHAOXIN, 0x7, 0x1b, X86_FEATURE_XMM4_2, false),
+ X86_MATCH_VENDOR_FAM_MODEL_FEATURE(ZHAOXIN, 0x7, 0x3b, X86_FEATURE_XMM4_2, false),
+ X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 0x6, X86_FEATURE_XMM4_2, false),
+ X86_MATCH_VENDOR_FAM_MODEL_FEATURE(CENTAUR, 0x7, 0x1b, X86_FEATURE_XMM4_2, false),
+ X86_MATCH_VENDOR_FAM_MODEL_FEATURE(CENTAUR, 0x7, 0x3b, X86_FEATURE_XMM4_2, false),
+ /*
+ * Positive entry; SSE-4.2 instructions include special purpose CRC32
+ * instructions.
+ */
+ X86_MATCH_FEATURE(X86_FEATURE_XMM4_2, true),
{}
};
MODULE_DEVICE_TABLE(x86cpu, crc32c_cpu_id);
static int __init crc32c_intel_mod_init(void)
{
- if (!x86_match_cpu(crc32c_cpu_id))
+ const struct x86_cpu_id *m = x86_match_cpu(crc32c_cpu_id);
+
+ if (!m || !m->driver_data)
return -ENODEV;
#ifdef CONFIG_X86_64
if (boot_cpu_has(X86_FEATURE_PCLMULQDQ)) {
--
2.7.4
