[PATCH v1 0/3] crypto: x86/crc32c-intel - Exclude some Zhaoxin CPUs

[PATCH v1 0/3] crypto: x86/crc32c-intel - Exclude some Zhaoxin CPUs

[Tony W Wang-oc]

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. Lower-level testing result is that with the same
input value the generic C implementation takes fewer time than the crc32c
instruction implementation on these CPUs. This case expect to use
crc32c-generic driver for these CPUs to get performance gain.

The presence of crc32c is enumerated by CPUID.01:ECX[SSE4.2] = 1, and
these CPUs other SSE4.2 instructions is ok.

Add a synthetic flag to indicates low performance CRC32C instruction
implementation, set this flag in Zhaoxin CPUs specific init phase,
and exclude CPUs which setting this flag from the driver crc32c-intel.

https://lkml.org/lkml/2020/12/21/789

Tony W Wang-oc (3):
  x86/cpufeatures: Add low performance CRC32C instruction CPU feature
  x86/cpu: Set low performance CRC32C flag on some Zhaoxin CPUs
  crypto: x86/crc32c-intel Exclude low performance CRC32C instruction
    CPUs

 arch/x86/crypto/crc32c-intel_glue.c | 5 +++++
 arch/x86/include/asm/cpufeatures.h  | 1 +
 arch/x86/kernel/cpu/centaur.c       | 7 +++++++
 arch/x86/kernel/cpu/cpuid-deps.c    | 1 +
 arch/x86/kernel/cpu/zhaoxin.c       | 6 ++++++
 5 files changed, 20 insertions(+)

-- 
2.7.4

[PATCH v1 1/3] x86/cpufeatures: Add low performance CRC32C instruction CPU feature

[Tony W Wang-oc]

SSE4.2 on Zhaoxin CPUs are compatible with Intel. The presence of
CRC32C instruction is enumerated by CPUID.01H:ECX.SSE4_2[bit 20] = 1.
Some Zhaoxin CPUs declare support SSE4.2 instruction sets but their
CRC32C instruction are working with low performance.

Add a synthetic CPU flag to indicates that the CRC32C instruction is
not working as intended. This low performance CRC32C instruction flag
is depend on X86_FEATURE_XMM4_2.

Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/kernel/cpu/cpuid-deps.c   | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 84b8878..9e8151b 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -292,6 +292,7 @@
 #define X86_FEATURE_FENCE_SWAPGS_KERNEL	(11*32+ 5) /* "" LFENCE in kernel entry SWAPGS path */
 #define X86_FEATURE_SPLIT_LOCK_DETECT	(11*32+ 6) /* #AC for split lock */
 #define X86_FEATURE_PER_THREAD_MBA	(11*32+ 7) /* "" Per-thread Memory Bandwidth Allocation */
+#define X86_FEATURE_CRC32C		(11*32+ 8) /* "" Low performance CRC32C instruction */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
 #define X86_FEATURE_AVX512_BF16		(12*32+ 5) /* AVX512 BFLOAT16 instructions */
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index 42af31b6..7d7fca7 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -72,6 +72,7 @@ static const struct cpuid_dep cpuid_deps[] = {
 	{ X86_FEATURE_AVX512_FP16,		X86_FEATURE_AVX512BW  },
 	{ X86_FEATURE_ENQCMD,			X86_FEATURE_XSAVES    },
 	{ X86_FEATURE_PER_THREAD_MBA,		X86_FEATURE_MBA       },
+	{ X86_FEATURE_CRC32C,			X86_FEATURE_XMM4_2    },
 	{}
 };
 
-- 
2.7.4

Re: [PATCH v1 1/3] x86/cpufeatures: Add low performance CRC32C instruction CPU feature

[Borislav Petkov]

On Thu, Jan 07, 2021 at 02:19:06PM +0800, Tony W Wang-oc wrote:
> SSE4.2 on Zhaoxin CPUs are compatible with Intel. The presence of
> CRC32C instruction is enumerated by CPUID.01H:ECX.SSE4_2[bit 20] = 1.
> Some Zhaoxin CPUs declare support SSE4.2 instruction sets but their
> CRC32C instruction are working with low performance.
> 
> Add a synthetic CPU flag to indicates that the CRC32C instruction is
> not working as intended. This low performance CRC32C instruction flag
> is depend on X86_FEATURE_XMM4_2.
> 
> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/kernel/cpu/cpuid-deps.c   | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 84b8878..9e8151b 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -292,6 +292,7 @@
>  #define X86_FEATURE_FENCE_SWAPGS_KERNEL	(11*32+ 5) /* "" LFENCE in kernel entry SWAPGS path */
>  #define X86_FEATURE_SPLIT_LOCK_DETECT	(11*32+ 6) /* #AC for split lock */
>  #define X86_FEATURE_PER_THREAD_MBA	(11*32+ 7) /* "" Per-thread Memory Bandwidth Allocation */
> +#define X86_FEATURE_CRC32C		(11*32+ 8) /* "" Low performance CRC32C instruction */

Didn't hpa say to create a BUG flag for it - X86_BUG...? Low performance
insn sounds like a bug and not a feature to me.

And call it X86_BUG_CRC32C_SLOW or ..._UNUSABLE to denote what it means.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v1 1/3] x86/cpufeatures: Add low performance CRC32C instruction CPU feature

[Tony W Wang-oc]

On 07/01/2021 14:37, Borislav Petkov wrote:
> On Thu, Jan 07, 2021 at 02:19:06PM +0800, Tony W Wang-oc wrote:
>> SSE4.2 on Zhaoxin CPUs are compatible with Intel. The presence of
>> CRC32C instruction is enumerated by CPUID.01H:ECX.SSE4_2[bit 20] = 1.
>> Some Zhaoxin CPUs declare support SSE4.2 instruction sets but their
>> CRC32C instruction are working with low performance.
>>
>> Add a synthetic CPU flag to indicates that the CRC32C instruction is
>> not working as intended. This low performance CRC32C instruction flag
>> is depend on X86_FEATURE_XMM4_2.
>>
>> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
>> ---
>>  arch/x86/include/asm/cpufeatures.h | 1 +
>>  arch/x86/kernel/cpu/cpuid-deps.c   | 1 +
>>  2 files changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index 84b8878..9e8151b 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -292,6 +292,7 @@
>>  #define X86_FEATURE_FENCE_SWAPGS_KERNEL	(11*32+ 5) /* "" LFENCE in kernel entry SWAPGS path */
>>  #define X86_FEATURE_SPLIT_LOCK_DETECT	(11*32+ 6) /* #AC for split lock */
>>  #define X86_FEATURE_PER_THREAD_MBA	(11*32+ 7) /* "" Per-thread Memory Bandwidth Allocation */
>> +#define X86_FEATURE_CRC32C		(11*32+ 8) /* "" Low performance CRC32C instruction */
> 
> Didn't hpa say to create a BUG flag for it - X86_BUG...? Low performance
> insn sounds like a bug and not a feature to me.
> 
> And call it X86_BUG_CRC32C_SLOW or ..._UNUSABLE to denote what it means.
> 

This issue will be enhanced by hardware and patch submit will be pending.

Sincerely
Tonyw

Re: [PATCH v1 1/3] x86/cpufeatures: Add low performance CRC32C instruction CPU feature

[Borislav Petkov]

On Mon, Jan 11, 2021 at 06:51:59PM +0800, Tony W Wang-oc wrote:
> This issue will be enhanced by hardware and patch submit will be pending.

I have no clue what that has to do with your current patch... you might
need to explain more verbosely.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v1 1/3] x86/cpufeatures: Add low performance CRC32C instruction CPU feature

[Tony W Wang-oc]

On 11/01/2021 19:03, Borislav Petkov wrote:
> On Mon, Jan 11, 2021 at 06:51:59PM +0800, Tony W Wang-oc wrote:
>> This issue will be enhanced by hardware and patch submit will be pending.
> 
> I have no clue what that has to do with your current patch... you might
> need to explain more verbosely.
> 

After internal research, decided to fix the low performance crc32c
instruction issue on these Zhaoxin CPUs by microcode. So, do not need
this patch anymore.

Sincerely
Tonyw

Re: [PATCH v1 1/3] x86/cpufeatures: Add low performance CRC32C instruction CPU feature

[hpa]

On January 6, 2021 10:37:50 PM PST, Borislav Petkov <bp@alien8.de> wrote:
>On Thu, Jan 07, 2021 at 02:19:06PM +0800, Tony W Wang-oc wrote:
>> SSE4.2 on Zhaoxin CPUs are compatible with Intel. The presence of
>> CRC32C instruction is enumerated by CPUID.01H:ECX.SSE4_2[bit 20] = 1.
>> Some Zhaoxin CPUs declare support SSE4.2 instruction sets but their
>> CRC32C instruction are working with low performance.
>> 
>> Add a synthetic CPU flag to indicates that the CRC32C instruction is
>> not working as intended. This low performance CRC32C instruction flag
>> is depend on X86_FEATURE_XMM4_2.
>> 
>> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
>> ---
>>  arch/x86/include/asm/cpufeatures.h | 1 +
>>  arch/x86/kernel/cpu/cpuid-deps.c   | 1 +
>>  2 files changed, 2 insertions(+)
>> 
>> diff --git a/arch/x86/include/asm/cpufeatures.h
>b/arch/x86/include/asm/cpufeatures.h
>> index 84b8878..9e8151b 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -292,6 +292,7 @@
>>  #define X86_FEATURE_FENCE_SWAPGS_KERNEL	(11*32+ 5) /* "" LFENCE in
>kernel entry SWAPGS path */
>>  #define X86_FEATURE_SPLIT_LOCK_DETECT	(11*32+ 6) /* #AC for split
>lock */
>>  #define X86_FEATURE_PER_THREAD_MBA	(11*32+ 7) /* "" Per-thread
>Memory Bandwidth Allocation */
>> +#define X86_FEATURE_CRC32C		(11*32+ 8) /* "" Low performance CRC32C
>instruction */
>
>Didn't hpa say to create a BUG flag for it - X86_BUG...? Low
>performance
>insn sounds like a bug and not a feature to me.
>
>And call it X86_BUG_CRC32C_SLOW or ..._UNUSABLE to denote what it
>means.
>
>Thx.

Yes, it should be a BUG due to the inclusion properties of BUG v FEATURE.
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[PATCH v1 2/3] x86/cpu: Set low performance CRC32C flag on some Zhaoxin CPUs

[Tony W Wang-oc]

Some Zhaoxin CPUs declare support SSE4.2 instruction sets but
having a CRC32C instruction implementation that not working as
intended. Set low performance CRC32C flag on these CPUs for later
use.

Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
---
 arch/x86/kernel/cpu/centaur.c | 7 +++++++
 arch/x86/kernel/cpu/zhaoxin.c | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c
index 345f7d9..13e6fbe 100644
--- a/arch/x86/kernel/cpu/centaur.c
+++ b/arch/x86/kernel/cpu/centaur.c
@@ -109,6 +109,13 @@ static void early_init_centaur(struct cpuinfo_x86 *c)
 		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
 		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
 	}
+
+	/*
+	 * These CPUs declare support SSE4.2 instruction sets but
+	 * having low performance CRC32C instruction implementation.
+	 */
+	if (c->x86 == 0x6 || (c->x86 == 0x7 && c->x86_model <= 0x3b))
+		set_cpu_cap(c, X86_FEATURE_CRC32C);
 }
 
 static void init_centaur(struct cpuinfo_x86 *c)
diff --git a/arch/x86/kernel/cpu/zhaoxin.c b/arch/x86/kernel/cpu/zhaoxin.c
index 05fa4ef..837ec65 100644
--- a/arch/x86/kernel/cpu/zhaoxin.c
+++ b/arch/x86/kernel/cpu/zhaoxin.c
@@ -79,6 +79,12 @@ static void early_init_zhaoxin(struct cpuinfo_x86 *c)
 			c->x86_coreid_bits = get_count_order((ebx >> 16) & 0xff);
 	}
 
+	/*
+	 * These CPUs declare support SSE4.2 instruction sets but
+	 * having low performance CRC32C instruction implementation.
+	 */
+	if (c->x86 == 0x6 || (c->x86 == 0x7 && c->x86_model <= 0x3b))
+		set_cpu_cap(c, X86_FEATURE_CRC32C);
 }
 
 static void init_zhaoxin(struct cpuinfo_x86 *c)
-- 
2.7.4

Re: [PATCH v1 2/3] x86/cpu: Set low performance CRC32C flag on some Zhaoxin CPUs

[Dave Hansen]

On 1/6/21 10:19 PM, Tony W Wang-oc wrote:
> +	/*
> +	 * These CPUs declare support SSE4.2 instruction sets but
> +	 * having low performance CRC32C instruction implementation.
> +	 */
> +	if (c->x86 == 0x6 || (c->x86 == 0x7 && c->x86_model <= 0x3b))
> +		set_cpu_cap(c, X86_FEATURE_CRC32C);
>  }

On the Intel side, we've tried to move away from open-coded model
numbers.  Say another CPU is released that has a microarchitecture close
to 0x3b, but has a model of 0x3c.  It's a *LOT* easier to grep for
INTEL_FAM6_NEHALEM (or whatever) than 0x3c.  See:

	arch/x86/include/asm/intel-family.h

for examples.

Re: [PATCH v1 2/3] x86/cpu: Set low performance CRC32C flag on some Zhaoxin CPUs

[Tony W Wang-oc]

On 07/01/2021 23:52, Dave Hansen wrote:
> On 1/6/21 10:19 PM, Tony W Wang-oc wrote:
>> +	/*
>> +	 * These CPUs declare support SSE4.2 instruction sets but
>> +	 * having low performance CRC32C instruction implementation.
>> +	 */
>> +	if (c->x86 == 0x6 || (c->x86 == 0x7 && c->x86_model <= 0x3b))
>> +		set_cpu_cap(c, X86_FEATURE_CRC32C);
>>  }
> 
> On the Intel side, we've tried to move away from open-coded model
> numbers.  Say another CPU is released that has a microarchitecture close
> to 0x3b, but has a model of 0x3c.  It's a *LOT* easier to grep for
> INTEL_FAM6_NEHALEM (or whatever) than 0x3c.  See:
> 
> 	arch/x86/include/asm/intel-family.h
> 
> for examples.
> .
> 

Got it, thanks for your suggestion.

Sincerely
Tonyw

[PATCH v1 3/3] crypto: x86/crc32c-intel Exclude low performance CRC32C instruction CPUs

[Tony W Wang-oc]

Low performance CRC32C instruction CPUs expect to use the driver
crc32c-generic. So remove these CPUs support from crc32c-intel.

Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
---
 arch/x86/crypto/crc32c-intel_glue.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/crypto/crc32c-intel_glue.c b/arch/x86/crypto/crc32c-intel_glue.c
index feccb52..1b6d289 100644
--- a/arch/x86/crypto/crc32c-intel_glue.c
+++ b/arch/x86/crypto/crc32c-intel_glue.c
@@ -224,6 +224,11 @@ static int __init crc32c_intel_mod_init(void)
 {
 	if (!x86_match_cpu(crc32c_cpu_id))
 		return -ENODEV;
+
+	/* Don't merit use low performance CRC32C instruction */
+	if (boot_cpu_has(X86_FEATURE_CRC32C))
+		return -ENODEV;
+
 #ifdef CONFIG_X86_64
 	if (boot_cpu_has(X86_FEATURE_PCLMULQDQ)) {
 		alg.update = crc32c_pcl_intel_update;
-- 
2.7.4