From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Nadav Amit <namit@cs.technion.ac.il>,
Gleb Natapov <gleb@kernel.org>
Subject: Re: [PATCH 7/8] KVM: x86: avoid logical_map when it is invalid
Date: Fri, 30 Jan 2015 18:09:10 +0100 [thread overview]
Message-ID: <20150130170909.GE27414@potion.redhat.com> (raw)
In-Reply-To: <54CB9EE3.3030804@redhat.com>
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
>
> x & (x - 1) is really hweight8(new->mode) > 1. So if new->mode == 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 "!=" :)
> >> Please add a comment to kvm_irq_delivery_to_apic_fast to explain what
> >> you are doing.
> >
> > Would naming it kvm_apic_need_slow_delivery(), or something, be enough?
>
> Or kvm_apic_map_valid() perhaps?
Sure, thanks.
next prev parent reply other threads:[~2015-01-30 17:09 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-29 21:48 [PATCH 0/8] KVM: minor APIC fixes and cleanups Radim Krčmář
2015-01-29 21:48 ` [PATCH 1/8] KVM: x86: return bool from kvm_apic_match*() Radim Krčmář
2015-01-29 22:10 ` Joe Perches
2015-01-30 8:50 ` Paolo Bonzini
2015-01-29 21:48 ` [PATCH 2/8] KVM: x86: cleanup kvm_apic_match_*() Radim Krčmář
2015-01-30 8:52 ` Paolo Bonzini
2015-01-30 13:06 ` Radim Krčmář
2015-02-02 14:26 ` Radim Krčmář
2015-02-02 14:28 ` Paolo Bonzini
2015-02-02 14:30 ` Radim Krčmář
2015-02-02 14:29 ` Radim Krčmář
2015-01-29 21:48 ` [PATCH 3/8] KVM: x86: replace 0 with APIC_DEST_PHYSICAL Radim Krčmář
2015-01-29 21:48 ` [PATCH 4/8] KVM: x86: fix x2apic logical address matching Radim Krčmář
2015-01-29 21:48 ` [PATCH 5/8] KVM: x86: use MDA for interrupt matching Radim Krčmář
2015-01-30 9:03 ` Paolo Bonzini
2015-01-30 13:09 ` Radim Krčmář
2015-01-29 21:48 ` [PATCH 6/8] KVM: x86: allow mixed APIC mode broadcast Radim Krčmář
2015-01-29 21:48 ` [PATCH 7/8] KVM: x86: avoid logical_map when it is invalid Radim Krčmář
2015-01-30 9:19 ` Paolo Bonzini
2015-01-30 14:21 ` Radim Krčmář
2015-01-30 14:21 ` Paolo Bonzini
2015-01-30 9:38 ` Paolo Bonzini
2015-01-30 14:56 ` Radim Krčmář
2015-01-30 15:10 ` Paolo Bonzini
2015-01-30 17:09 ` Radim Krčmář [this message]
2015-01-29 21:48 ` [PATCH 8/8] KVM: x86: simplify kvm_apic_map Radim Krčmář
2015-01-30 9:18 ` Paolo Bonzini
2015-01-30 15:14 ` Radim Krčmář
2015-01-30 15:23 ` Paolo Bonzini
2015-01-30 16:57 ` Radim Krčmář
2015-01-30 21:15 ` Paolo Bonzini
2015-01-30 9:22 ` [PATCH 0/8] KVM: minor APIC fixes and cleanups Paolo Bonzini
2015-01-30 15:20 ` Radim Krčmář
2015-01-30 15:24 ` Paolo Bonzini
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