From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [PATCH 7/8] KVM: x86: avoid logical_map when it is invalid
Date: Fri, 30 Jan 2015 18:09:10 +0100
Message-ID: <20150130170909.GE27414@potion.redhat.com>
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Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Nadav Amit <namit@cs.technion.ac.il>,
	Gleb Natapov <gleb@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
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2015-01-30 16:10+0100, Paolo Bonzini:
> On 30/01/2015 15:56, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote:
> > Do you know of a difference with it?
> >   new->mode & (new->mode - 1)   |  hweight8(new->mode) !=3D 1
> >     lea    -0x1(%rax),%edi      |    popcnt %edi,%eax
> >     test   %eax,%edi            |    cmp    $1,%eax
>=20
> x & (x - 1) is really hweight8(new->mode) > 1.  So if new->mode =3D=3D=
 0 it
> would have a different result.

(I was thinking if execution profile of those two instructions isn't
 vastly different.

 ">" in this check works too ... later it seemed like it was pushing
 lucky coincidence too far, so it ended as "!=3D" :)

> >> Please add a comment to kvm_irq_delivery_to_apic_fast to explain w=
hat
> >> you are doing.
> >=20
> > Would naming it kvm_apic_need_slow_delivery(), or something, be eno=
ugh?
>=20
> Or kvm_apic_map_valid() perhaps?

Sure, thanks.