2015-01-30 16:10+0100, Paolo Bonzini:
> On 30/01/2015 15:56, Radim Krčmář wrote:
> > Do you know of a difference with it?
> > new->mode & (new->mode - 1) | hweight8(new->mode) != 1
> > lea-0x1(%rax),%edi |popcnt %edi,%eax
> > test %eax,%edi|cmp$1,%eax
On 30/01/2015 15:56, Radim Krčmář wrote:
> 2015-01-30 10:38+0100, Paolo Bonzini:
>> On 29/01/2015 22:48, Radim Krčmář wrote:
>>> + if (hweight8(new->mode) != 1)
>>
>> Better (more optimized):
>>
>> if (new->mode & (new->mode - 1))
>
> True, hweight needs to have X86_FEATURE_POPCNT
2015-01-30 10:38+0100, Paolo Bonzini:
> On 29/01/2015 22:48, Radim Krčmář wrote:
> > + if (hweight8(new->mode) != 1)
>
> Better (more optimized):
>
> if (new->mode & (new->mode - 1))
True, hweight needs to have X86_FEATURE_POPCNT to be efficient ...
Do you know of a difference w
On 30/01/2015 15:21, Radim Krčmář wrote:
> Yes, but it would only matter if the OS set LDR on them.
> I mark x2APIC with perfectly configured xAPIC on unused processors as
> "weird" ... (Linux 3.18 and 2.6.32 doesn't do it.)
Ok.
Paolo
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2015-01-30 10:19+0100, Paolo Bonzini:
> On 29/01/2015 22:48, Radim Krčmář wrote:
> > We want to support mixed modes and the easiest solution is to avoid
> > optimizing those weird and unlikely scenarios.
>
> Hmm, what happens if use maxcpus to disable some CPUs at startup?
Their APICs are kept sw
On 29/01/2015 22:48, Radim Krčmář wrote:
> We want to support mixed modes and the easiest solution is to avoid
> optimizing those weird and unlikely scenarios.
>
> Signed-off-by: Radim Krčmář
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/lapic.c| 16 +++
On 29/01/2015 22:48, Radim Krčmář wrote:
> We want to support mixed modes and the easiest solution is to avoid
> optimizing those weird and unlikely scenarios.
Hmm, what happens if use maxcpus to disable some CPUs at startup? Could
the disabled CPUs remain in xapic mode while the others move to
We want to support mixed modes and the easiest solution is to avoid
optimizing those weird and unlikely scenarios.
Signed-off-by: Radim Krčmář
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/lapic.c| 16
arch/x86/kvm/lapic.h| 4
3 files cha
