* [V3] x86/cpuid: AVX-512 Feature Detection
@ 2016-06-29 11:27 Luwei Kang
2016-06-29 11:45 ` Kang, Luwei
2016-06-29 14:29 ` Jan Beulich
0 siblings, 2 replies; 4+ messages in thread
From: Luwei Kang @ 2016-06-29 11:27 UTC (permalink / raw)
To: xen-devel; +Cc: andrew.cooper3, chao.p.peng, Luwei Kang, yong.y.wang, jbeulich
AVX-512 is an extention of AVX2. Its spec can be found at:
https://software.intel.com/sites/default/files/managed/b4/3a/319433-024.pdf
This patch detects AVX-512 features by CPUID.
Signed-off-by: Luwei Kang <luwei.kang@intel.com>
---
[V3]
1.adjust dependencies between features.
[V2]
1.one per bit, change from
> + xstate_size = max(xstate_size,
> + xstate_offsets[_XSTATE_HI_ZMM] +
> + xstate_sizes[_XSTATE_HI_ZMM]);
to
xstate_size = max(xstate_size,
xstate_offsets[_XSTATE_OPMASK] +
xstate_sizes[_XSTATE_OPMASK]);
xstate_size = max(xstate_size,
xstate_offsets[_XSTATE_ZMM] +
xstate_sizes[_XSTATE_ZMM]);
xstate_size = max(xstate_size,
xstate_offsets[_XSTATE_HI_ZMM] +
xstate_sizes[_XSTATE_HI_ZMM]);
2.change form
domain_cpuid(currd, 0x07, 0, &tmp, &_ebx, &tmp, &tmp);
to
domain_cpuid(currd, 7, 0, &tmp, &_ebx, &tmp, &tmp);
3.add dependencies between features in xen/tools/gen-cpuid.py
4.split the cpuid call just like the way the hvm_cpuid() side works.
xen/arch/x86/hvm/hvm.c | 14 ++++++++++++++
xen/arch/x86/traps.c | 22 +++++++++++++++++++++-
xen/include/public/arch-x86/cpufeatureset.h | 9 +++++++++
xen/tools/gen-cpuid.py | 11 +++++++++++
4 files changed, 55 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index c89ab6e..7696b1e 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3474,6 +3474,20 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
xstate_sizes[_XSTATE_BNDCSR]);
}
+ if ( _ebx & cpufeat_mask(X86_FEATURE_AVX512F) )
+ {
+ xfeature_mask |= XSTATE_OPMASK | XSTATE_ZMM | XSTATE_HI_ZMM;
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_OPMASK] +
+ xstate_sizes[_XSTATE_OPMASK]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_ZMM] +
+ xstate_sizes[_XSTATE_ZMM]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_HI_ZMM] +
+ xstate_sizes[_XSTATE_HI_ZMM]);
+ }
+
if ( _ecx & cpufeat_mask(X86_FEATURE_PKU) )
{
xfeature_mask |= XSTATE_PKRU;
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 767d0b0..8fb697b 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -975,7 +975,7 @@ void pv_cpuid(struct cpu_user_regs *regs)
switch ( leaf )
{
- uint32_t tmp, _ecx;
+ uint32_t tmp, _ecx, _ebx;
case 0x00000001:
c &= pv_featureset[FEATURESET_1c];
@@ -1157,6 +1157,26 @@ void pv_cpuid(struct cpu_user_regs *regs)
xstate_sizes[_XSTATE_YMM]);
}
+ if ( !is_control_domain(currd) && !is_hardware_domain(currd) )
+ domain_cpuid(currd, 7, 0, &tmp, &_ebx, &tmp, &tmp);
+ else
+ cpuid_count(7, 0, &tmp, &_ebx, &tmp, &tmp);
+ _ebx &= pv_featureset[FEATURESET_7b0];
+
+ if ( _ebx & cpufeat_mask(X86_FEATURE_AVX512F) )
+ {
+ xfeature_mask |= XSTATE_OPMASK | XSTATE_ZMM | XSTATE_HI_ZMM;
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_OPMASK] +
+ xstate_sizes[_XSTATE_OPMASK]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_ZMM] +
+ xstate_sizes[_XSTATE_ZMM]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_HI_ZMM] +
+ xstate_sizes[_XSTATE_HI_ZMM]);
+ }
+
a = (uint32_t)xfeature_mask;
d = (uint32_t)(xfeature_mask >> 32);
c = xstate_size;
diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h
index 39acf8c..9320c9e 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -206,15 +206,24 @@ XEN_CPUFEATURE(PQM, 5*32+12) /* Platform QoS Monitoring */
XEN_CPUFEATURE(NO_FPU_SEL, 5*32+13) /*! FPU CS/DS stored as zero */
XEN_CPUFEATURE(MPX, 5*32+14) /*S Memory Protection Extensions */
XEN_CPUFEATURE(PQE, 5*32+15) /* Platform QoS Enforcement */
+XEN_CPUFEATURE(AVX512F, 5*32+16) /*A AVX-512 Foundation Instructions */
+XEN_CPUFEATURE(AVX512DQ, 5*32+17) /*A AVX-512 Doubleword & Quadword Instrs */
XEN_CPUFEATURE(RDSEED, 5*32+18) /*A RDSEED instruction */
XEN_CPUFEATURE(ADX, 5*32+19) /*A ADCX, ADOX instructions */
XEN_CPUFEATURE(SMAP, 5*32+20) /*S Supervisor Mode Access Prevention */
+XEN_CPUFEATURE(AVX512IFMA, 5*32+21) /*A AVX-512 Integer Fused Multiply Add */
XEN_CPUFEATURE(CLFLUSHOPT, 5*32+23) /*A CLFLUSHOPT instruction */
XEN_CPUFEATURE(CLWB, 5*32+24) /*A CLWB instruction */
+XEN_CPUFEATURE(AVX512PF, 5*32+26) /*A AVX-512 Prefetch Instructions */
+XEN_CPUFEATURE(AVX512ER, 5*32+27) /*A AVX-512 Exponent & Reciprocal Instrs */
+XEN_CPUFEATURE(AVX512CD, 5*32+28) /*A AVX-512 Conflict Detection Instrs */
XEN_CPUFEATURE(SHA, 5*32+29) /*A SHA1 & SHA256 instructions */
+XEN_CPUFEATURE(AVX512BW, 5*32+30) /*A AVX-512 Byte and Word Instructions */
+XEN_CPUFEATURE(AVX512VL, 5*32+31) /*A AVX-512 Vector Length Extensions */
/* Intel-defined CPU features, CPUID level 0x00000007:0.ecx, word 6 */
XEN_CPUFEATURE(PREFETCHWT1, 6*32+ 0) /*A PREFETCHWT1 instruction */
+XEN_CPUFEATURE(AVX512VBMI, 6*32+ 1) /*A AVX-512 Vector Byte Manipulation Instrs */
XEN_CPUFEATURE(PKU, 6*32+ 3) /*H Protection Keys for Userspace */
XEN_CPUFEATURE(OSPKE, 6*32+ 4) /*! OS Protection Keys Enable */
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 7c45eca..cf7bb67 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -243,6 +243,17 @@ def crunch_numbers(state):
# AMD K6-2+ and K6-III processors shipped with 3DNow+, beyond the
# standard 3DNow in the earlier K6 processors.
_3DNOW: [_3DNOWEXT],
+
+ # AVX2 is an extension to AVX, providing mainly new integer instructions.
+ # In principle, AVX512 only depends on YMM register state, but many AVX2
+ # instructions are extended by AVX512F to 512-bit forms.
+ AVX2: [AVX512F],
+
+ # AVX512F is taken to mean hardware support for EVEX encoded instructions,
+ # 512bit registers, and the instructions themselves. All further AVX512 features
+ # are built on top of AVX512F
+ AVX512F: [AVX512DQ, AVX512IFMA, AVX512PF, AVX512ER, AVX512CD,
+ AVX512BW, AVX512VL, AVX512VBMI],
}
deep_features = tuple(sorted(deps.keys()))
--
2.7.4
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Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [V3] x86/cpuid: AVX-512 Feature Detection
2016-06-29 11:27 [V3] x86/cpuid: AVX-512 Feature Detection Luwei Kang
@ 2016-06-29 11:45 ` Kang, Luwei
2016-06-29 14:24 ` Jan Beulich
2016-06-29 14:29 ` Jan Beulich
1 sibling, 1 reply; 4+ messages in thread
From: Kang, Luwei @ 2016-06-29 11:45 UTC (permalink / raw)
To: xen-devel; +Cc: andrew.cooper3, Peng, Chao P, Wang, Yong Y, jbeulich
From table 2-2 I can see that
AVX512F = AVX512F & AVX512VL
AVX512CD = AVX512F & AVX512VL & AVX512CD
AVX512DQ = AVX512F & AVX512VL & AVX512DQ
AVX512BW = AVX512F & AVX512VL & AVX512BW
AVX512IFMA = AVX512F & AVX512VL & AVX512IFMA
AVX512VBMI = AVX512F & AVX512VL & AVX512VBMI
From this depends list some AVX512 feature also depends on AVX512VL.
So the depends may like this:
AVX2: [AVX512F],
AVX512F: [AVX512DQ, AVX512IFMA, AVX512CD, AVX512BW, AVX512VBMI],
AVX512VL:[AVX512F, AVX512DQ, AVX512IFMA, AVX512CD, AVX512BW, AVX512VBMI]
But I have test on current hardware, this machine support AVX512F, AVX512PF, AVX512ER and AVX512CD,
do not support AVX512VL. I think there may have some conflict between spec and hardware.
The depends about AVX512VL should not add, or the AVX512 feature will not work.
So I think below depends is ok.
AVX2: [AVX512F],
AVX512F: [AVX512DQ, AVX512IFMA, AVX512PF, AVX512ER, AVX512CD,
AVX512BW, AVX512VL, AVX512VBMI],
Thanks,
Luwei Kang
-----Original Message-----
From: Kang, Luwei
Sent: Wednesday, June 29, 2016 7:28 PM
To: xen-devel@lists.xen.org
Cc: jbeulich@suse.com; andrew.cooper3@citrix.com; Wang, Yong Y <yong.y.wang@intel.com>; Peng, Chao P <chao.p.peng@intel.com>; Kang, Luwei <luwei.kang@intel.com>
Subject: [V3] x86/cpuid: AVX-512 Feature Detection
AVX-512 is an extention of AVX2. Its spec can be found at:
https://software.intel.com/sites/default/files/managed/b4/3a/319433-024.pdf
This patch detects AVX-512 features by CPUID.
Signed-off-by: Luwei Kang <luwei.kang@intel.com>
---
[V3]
1.adjust dependencies between features.
[V2]
1.one per bit, change from
> + xstate_size = max(xstate_size,
> + xstate_offsets[_XSTATE_HI_ZMM] +
> + xstate_sizes[_XSTATE_HI_ZMM]);
to
xstate_size = max(xstate_size,
xstate_offsets[_XSTATE_OPMASK] +
xstate_sizes[_XSTATE_OPMASK]);
xstate_size = max(xstate_size,
xstate_offsets[_XSTATE_ZMM] +
xstate_sizes[_XSTATE_ZMM]);
xstate_size = max(xstate_size,
xstate_offsets[_XSTATE_HI_ZMM] +
xstate_sizes[_XSTATE_HI_ZMM]); 2.change form
domain_cpuid(currd, 0x07, 0, &tmp, &_ebx, &tmp, &tmp);
to
domain_cpuid(currd, 7, 0, &tmp, &_ebx, &tmp, &tmp); 3.add dependencies between features in xen/tools/gen-cpuid.py 4.split the cpuid call just like the way the hvm_cpuid() side works.
xen/arch/x86/hvm/hvm.c | 14 ++++++++++++++
xen/arch/x86/traps.c | 22 +++++++++++++++++++++-
xen/include/public/arch-x86/cpufeatureset.h | 9 +++++++++
xen/tools/gen-cpuid.py | 11 +++++++++++
4 files changed, 55 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index c89ab6e..7696b1e 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3474,6 +3474,20 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
xstate_sizes[_XSTATE_BNDCSR]);
}
+ if ( _ebx & cpufeat_mask(X86_FEATURE_AVX512F) )
+ {
+ xfeature_mask |= XSTATE_OPMASK | XSTATE_ZMM | XSTATE_HI_ZMM;
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_OPMASK] +
+ xstate_sizes[_XSTATE_OPMASK]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_ZMM] +
+ xstate_sizes[_XSTATE_ZMM]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_HI_ZMM] +
+ xstate_sizes[_XSTATE_HI_ZMM]);
+ }
+
if ( _ecx & cpufeat_mask(X86_FEATURE_PKU) )
{
xfeature_mask |= XSTATE_PKRU; diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c index 767d0b0..8fb697b 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -975,7 +975,7 @@ void pv_cpuid(struct cpu_user_regs *regs)
switch ( leaf )
{
- uint32_t tmp, _ecx;
+ uint32_t tmp, _ecx, _ebx;
case 0x00000001:
c &= pv_featureset[FEATURESET_1c]; @@ -1157,6 +1157,26 @@ void pv_cpuid(struct cpu_user_regs *regs)
xstate_sizes[_XSTATE_YMM]);
}
+ if ( !is_control_domain(currd) && !is_hardware_domain(currd) )
+ domain_cpuid(currd, 7, 0, &tmp, &_ebx, &tmp, &tmp);
+ else
+ cpuid_count(7, 0, &tmp, &_ebx, &tmp, &tmp);
+ _ebx &= pv_featureset[FEATURESET_7b0];
+
+ if ( _ebx & cpufeat_mask(X86_FEATURE_AVX512F) )
+ {
+ xfeature_mask |= XSTATE_OPMASK | XSTATE_ZMM | XSTATE_HI_ZMM;
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_OPMASK] +
+ xstate_sizes[_XSTATE_OPMASK]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_ZMM] +
+ xstate_sizes[_XSTATE_ZMM]);
+ xstate_size = max(xstate_size,
+ xstate_offsets[_XSTATE_HI_ZMM] +
+ xstate_sizes[_XSTATE_HI_ZMM]);
+ }
+
a = (uint32_t)xfeature_mask;
d = (uint32_t)(xfeature_mask >> 32);
c = xstate_size;
diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h
index 39acf8c..9320c9e 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -206,15 +206,24 @@ XEN_CPUFEATURE(PQM, 5*32+12) /* Platform QoS Monitoring */
XEN_CPUFEATURE(NO_FPU_SEL, 5*32+13) /*! FPU CS/DS stored as zero */
XEN_CPUFEATURE(MPX, 5*32+14) /*S Memory Protection Extensions */
XEN_CPUFEATURE(PQE, 5*32+15) /* Platform QoS Enforcement */
+XEN_CPUFEATURE(AVX512F, 5*32+16) /*A AVX-512 Foundation Instructions */
+XEN_CPUFEATURE(AVX512DQ, 5*32+17) /*A AVX-512 Doubleword & Quadword Instrs */
XEN_CPUFEATURE(RDSEED, 5*32+18) /*A RDSEED instruction */
XEN_CPUFEATURE(ADX, 5*32+19) /*A ADCX, ADOX instructions */
XEN_CPUFEATURE(SMAP, 5*32+20) /*S Supervisor Mode Access Prevention */
+XEN_CPUFEATURE(AVX512IFMA, 5*32+21) /*A AVX-512 Integer Fused Multiply Add */
XEN_CPUFEATURE(CLFLUSHOPT, 5*32+23) /*A CLFLUSHOPT instruction */
XEN_CPUFEATURE(CLWB, 5*32+24) /*A CLWB instruction */
+XEN_CPUFEATURE(AVX512PF, 5*32+26) /*A AVX-512 Prefetch Instructions */
+XEN_CPUFEATURE(AVX512ER, 5*32+27) /*A AVX-512 Exponent & Reciprocal Instrs */
+XEN_CPUFEATURE(AVX512CD, 5*32+28) /*A AVX-512 Conflict Detection Instrs */
XEN_CPUFEATURE(SHA, 5*32+29) /*A SHA1 & SHA256 instructions */
+XEN_CPUFEATURE(AVX512BW, 5*32+30) /*A AVX-512 Byte and Word Instructions */
+XEN_CPUFEATURE(AVX512VL, 5*32+31) /*A AVX-512 Vector Length Extensions */
/* Intel-defined CPU features, CPUID level 0x00000007:0.ecx, word 6 */
XEN_CPUFEATURE(PREFETCHWT1, 6*32+ 0) /*A PREFETCHWT1 instruction */
+XEN_CPUFEATURE(AVX512VBMI, 6*32+ 1) /*A AVX-512 Vector Byte Manipulation Instrs */
XEN_CPUFEATURE(PKU, 6*32+ 3) /*H Protection Keys for Userspace */
XEN_CPUFEATURE(OSPKE, 6*32+ 4) /*! OS Protection Keys Enable */
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py index 7c45eca..cf7bb67 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -243,6 +243,17 @@ def crunch_numbers(state):
# AMD K6-2+ and K6-III processors shipped with 3DNow+, beyond the
# standard 3DNow in the earlier K6 processors.
_3DNOW: [_3DNOWEXT],
+
+ # AVX2 is an extension to AVX, providing mainly new integer instructions.
+ # In principle, AVX512 only depends on YMM register state, but many AVX2
+ # instructions are extended by AVX512F to 512-bit forms.
+ AVX2: [AVX512F],
+
+ # AVX512F is taken to mean hardware support for EVEX encoded instructions,
+ # 512bit registers, and the instructions themselves. All further AVX512 features
+ # are built on top of AVX512F
+ AVX512F: [AVX512DQ, AVX512IFMA, AVX512PF, AVX512ER, AVX512CD,
+ AVX512BW, AVX512VL, AVX512VBMI],
}
deep_features = tuple(sorted(deps.keys()))
--
2.7.4
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [V3] x86/cpuid: AVX-512 Feature Detection
2016-06-29 11:45 ` Kang, Luwei
@ 2016-06-29 14:24 ` Jan Beulich
0 siblings, 0 replies; 4+ messages in thread
From: Jan Beulich @ 2016-06-29 14:24 UTC (permalink / raw)
To: Luwei Kang; +Cc: andrew.cooper3, Chao P Peng, Yong Y Wang, xen-devel
>>> On 29.06.16 at 13:45, <luwei.kang@intel.com> wrote:
> From table 2-2 I can see that
> AVX512F = AVX512F & AVX512VL
> AVX512CD = AVX512F & AVX512VL & AVX512CD
> AVX512DQ = AVX512F & AVX512VL & AVX512DQ
> AVX512BW = AVX512F & AVX512VL & AVX512BW
> AVX512IFMA = AVX512F & AVX512VL & AVX512IFMA
> AVX512VBMI = AVX512F & AVX512VL & AVX512VBMI
>
> From this depends list some AVX512 feature also depends on AVX512VL.
You mis-interpreted that table - its left column header clearly says
"Usage of 256/128 Vector Lengths".
Jan
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [V3] x86/cpuid: AVX-512 Feature Detection
2016-06-29 11:27 [V3] x86/cpuid: AVX-512 Feature Detection Luwei Kang
2016-06-29 11:45 ` Kang, Luwei
@ 2016-06-29 14:29 ` Jan Beulich
1 sibling, 0 replies; 4+ messages in thread
From: Jan Beulich @ 2016-06-29 14:29 UTC (permalink / raw)
To: Luwei Kang; +Cc: andrew.cooper3, chao.p.peng, yong.y.wang, xen-devel
>>> On 29.06.16 at 13:27, <luwei.kang@intel.com> wrote:
> AVX-512 is an extention of AVX2. Its spec can be found at:
> https://software.intel.com/sites/default/files/managed/b4/3a/319433-024.pdf
> This patch detects AVX-512 features by CPUID.
>
> Signed-off-by: Luwei Kang <luwei.kang@intel.com>
> ---
> [V3]
> 1.adjust dependencies between features.
> [V2]
> 1.one per bit, change from
> > + xstate_size = max(xstate_size,
> > + xstate_offsets[_XSTATE_HI_ZMM] +
> > + xstate_sizes[_XSTATE_HI_ZMM]);
> to
> xstate_size = max(xstate_size,
> xstate_offsets[_XSTATE_OPMASK] +
> xstate_sizes[_XSTATE_OPMASK]);
> xstate_size = max(xstate_size,
> xstate_offsets[_XSTATE_ZMM] +
> xstate_sizes[_XSTATE_ZMM]);
> xstate_size = max(xstate_size,
> xstate_offsets[_XSTATE_HI_ZMM] +
> xstate_sizes[_XSTATE_HI_ZMM]);
> 2.change form
> domain_cpuid(currd, 0x07, 0, &tmp, &_ebx, &tmp, &tmp);
> to
> domain_cpuid(currd, 7, 0, &tmp, &_ebx, &tmp, &tmp);
> 3.add dependencies between features in xen/tools/gen-cpuid.py
> 4.split the cpuid call just like the way the hvm_cpuid() side works.
Especially item 1 is clearly to verbose; note how I said "brief" when
I asked for the revision log.
> --- a/xen/tools/gen-cpuid.py
> +++ b/xen/tools/gen-cpuid.py
> @@ -243,6 +243,17 @@ def crunch_numbers(state):
> # AMD K6-2+ and K6-III processors shipped with 3DNow+, beyond the
> # standard 3DNow in the earlier K6 processors.
> _3DNOW: [_3DNOWEXT],
> +
> + # AVX2 is an extension to AVX, providing mainly new integer instructions.
> + # In principle, AVX512 only depends on YMM register state, but many AVX2
> + # instructions are extended by AVX512F to 512-bit forms.
I realize you used the wording as suggested by Andrew, and while
his reply to my question about it meanwhile clarified what is meant,
I continue to think that the mentioning of YMM registers above is
misleading. May I suggest something like "AVX512 only takes YMM
register state as a prerequisite", subject to further improvement by
Andrew or another native speaker?
Apart from that the patch looks fine to me now.
Jan
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