Re: [PATCH RFC] kvm: x86: Expose AVX512_BF16 feature to guest
Hi Paolo,
On 6/24/2019 4:33 PM, Paolo Bonzini wrote:
On 24/06/19 05:10, Jing Liu wrote:
What do you think about @index in current function? Does it mean, we
need put cpuid from index to max subleaf to @entry[i]? If so, the logic
seems as follows,
if (index == 0) {
// Put subleaf 0 into @entry
// Put subleaf 1 into @entry[1]
} else if (index < entry->eax) {
// Put subleaf 1 into @entry
} else {
// Put all zero into @entry
}
But this seems not identical with other cases, for current caller
function. Or we can simply ignore @index in 0x07 and just put all
possible subleaf info back?
There are indeed quite some cleanups to be made there. Let me post a
series as soon as possible, and you can base your work on it.
Thanks. I just had another mail (replying you in this serial) appending
some codes to deal with case 7. If you prefer to firstly cleanup, I can
wait for the patch then. :)
Thanks,
Jing
Paolo
Re: [PATCH RFC] kvm: x86: Expose AVX512_BF16 feature to guest
On 24/06/19 05:10, Jing Liu wrote:
>> What do you think about @index in current function? Does it mean, we
>> need put cpuid from index to max subleaf to @entry[i]? If so, the logic
>> seems as follows,
>>
>> if (index == 0) {
>> // Put subleaf 0 into @entry
>> // Put subleaf 1 into @entry[1]
>> } else if (index < entry->eax) {
>> // Put subleaf 1 into @entry
>> } else {
>> // Put all zero into @entry
>> }
>>
>> But this seems not identical with other cases, for current caller
>> function. Or we can simply ignore @index in 0x07 and just put all
>> possible subleaf info back?
There are indeed quite some cleanups to be made there. Let me post a
series as soon as possible, and you can base your work on it.
Paolo
Re: [PATCH RFC] kvm: x86: Expose AVX512_BF16 feature to guest
Hi Paolo,
After thinking more, I found way to satisfy all cases in a easy way.
How about things like this?
@@ -507,12 +510,26 @@ static inline int __do_cpuid_ent(struct
kvm_cpuid_entry2 *entry, u32 fu
* if the host doesn't support it.
*/
entry->edx |= F(ARCH_CAPABILITIES);
+ } else if (index == 1) {
+ entry->eax &= kvm_cpuid_7_1_eax_x86_features;
+ entry->ebx = 0;
+ entry->ecx = 0;
+ entry->edx = 0;
} else {
+ entry->eax = 0;
entry->ebx = 0;
entry->ecx = 0;
entry->edx = 0;
}
- entry->eax = 0;
+
+ if (index == 0 && entry->eax >= 1) {
+ entry[1].eax &= kvm_cpuid_7_1_eax_x86_features;
+ entry[1].ebx = 0;
+ entry[1].ecx = 0;
+ entry[1].edx = 0;
+ entry[1].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+ ++*nent;
+ }
break;
}
Or you prefer that I update this into another version later?
Thanks!
Jing
On 6/20/2019 11:09 PM, Liu, Jing2 wrote:
Hi Paolo,
On 6/20/2019 8:16 PM, Paolo Bonzini wrote:
On 20/06/19 13:21, Jing Liu wrote:
+ for (i = 1; i <= times; i++) {
+ if (*nent >= maxnent)
+ goto out;
+ do_cpuid_1_ent([i], function, i);
+ entry[i].eax &= F(AVX512_BF16);
+ entry[i].ebx = 0;
+ entry[i].ecx = 0;
+ entry[i].edx = 0;
+ entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+ ++*nent;
This woud be wrong for i > 1, so instead make this
if (entry->eax >= 1)
I am confused about the @index parameter. @index seems not used for
every case except 0x07. Since the caller function only has @index=0, so
all other cases except 0x07 put cpuid info from subleaf=0 to max subleaf.
What do you think about @index in current function? Does it mean, we
need put cpuid from index to max subleaf to @entry[i]? If so, the logic
seems as follows,
if (index == 0) {
// Put subleaf 0 into @entry
// Put subleaf 1 into @entry[1]
} else if (index < entry->eax) {
// Put subleaf 1 into @entry
} else {
// Put all zero into @entry
}
But this seems not identical with other cases, for current caller
function. Or we can simply ignore @index in 0x07 and just put all possible
subleaf info back?
and define F(AVX512_BF16) as a new constant kvm_cpuid_7_1_eax_features.
Got it.
Thanks,
Jing
Paolo
Re: [PATCH RFC] kvm: x86: Expose AVX512_BF16 feature to guest
Hi Paolo,
On 6/20/2019 8:16 PM, Paolo Bonzini wrote:
On 20/06/19 13:21, Jing Liu wrote:
+ for (i = 1; i <= times; i++) {
+ if (*nent >= maxnent)
+ goto out;
+ do_cpuid_1_ent([i], function, i);
+ entry[i].eax &= F(AVX512_BF16);
+ entry[i].ebx = 0;
+ entry[i].ecx = 0;
+ entry[i].edx = 0;
+ entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+ ++*nent;
This woud be wrong for i > 1, so instead make this
if (entry->eax >= 1)
I am confused about the @index parameter. @index seems not used for
every case except 0x07. Since the caller function only has @index=0, so
all other cases except 0x07 put cpuid info from subleaf=0 to max subleaf.
What do you think about @index in current function? Does it mean, we
need put cpuid from index to max subleaf to @entry[i]? If so, the logic
seems as follows,
if (index == 0) {
// Put subleaf 0 into @entry
// Put subleaf 1 into @entry[1]
} else if (index < entry->eax) {
// Put subleaf 1 into @entry
} else {
// Put all zero into @entry
}
But this seems not identical with other cases, for current caller
function. Or we can simply ignore @index in 0x07 and just put all possible
subleaf info back?
and define F(AVX512_BF16) as a new constant kvm_cpuid_7_1_eax_features.
Got it.
Thanks,
Jing
Paolo
Re: [PATCH RFC] kvm: x86: Expose AVX512_BF16 feature to guest
On 20/06/19 13:21, Jing Liu wrote:
> + for (i = 1; i <= times; i++) {
> + if (*nent >= maxnent)
> + goto out;
> + do_cpuid_1_ent([i], function, i);
> + entry[i].eax &= F(AVX512_BF16);
> + entry[i].ebx = 0;
> + entry[i].ecx = 0;
> + entry[i].edx = 0;
> + entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> + ++*nent;
This woud be wrong for i > 1, so instead make this
if (entry->eax >= 1)
and define F(AVX512_BF16) as a new constant kvm_cpuid_7_1_eax_features.
Paolo
[PATCH RFC] kvm: x86: Expose AVX512_BF16 feature to guest
AVX512 BFLOAT16 instructions support 16-bit BFLOAT16 floating-point
format (BF16) for deep learning optimization.
Intel adds AVX512 BFLOAT16 feature in CooperLake, which is CPUID.7.1.EAX[5].
Detailed information of the CPUID bit can be found here,
https://software.intel.com/sites/default/files/managed/c5/15/\
architecture-instruction-set-extensions-programming-reference.pdf.
Signed-off-by: Jing Liu
---
arch/x86/kvm/cpuid.c | 16 ++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e18a9f9..10be53f 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -484,6 +484,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2
*entry, u32 function,
entry->edx = 0;
break;
case 7: {
+ int i, times = entry->eax;
entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
/* Mask ebx against host capability word 9 */
if (index == 0) {
@@ -507,12 +508,23 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2
*entry, u32 function,
* if the host doesn't support it.
*/
entry->edx |= F(ARCH_CAPABILITIES);
- } else {
+ } else if (index > times) {
+ entry->eax = 0;
entry->ebx = 0;
entry->ecx = 0;
entry->edx = 0;
}
- entry->eax = 0;
+ for (i = 1; i <= times; i++) {
+ if (*nent >= maxnent)
+ goto out;
+ do_cpuid_1_ent([i], function, i);
+ entry[i].eax &= F(AVX512_BF16);
+ entry[i].ebx = 0;
+ entry[i].ecx = 0;
+ entry[i].edx = 0;
+ entry[i].flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+ ++*nent;
+ }
break;
}
case 9:
--
1.8.3.1
