From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [PATCH v4 1/2] KVM: remove NULL return path for vcpu ids >=
 KVM_MAX_VCPUS
Date: Wed, 27 Apr 2016 16:40:14 +0200
Message-ID: <20160427144010.GA27247@potion>
References: <146124809455.32509.15232948272580716135.stgit@bahia.huguette.org>
 <146124810201.32509.2946887043729554992.stgit@bahia.huguette.org>
 <20160427054052.Horde.SSxGXKxS_wcijUfLJchjWw2@ltc.linux.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Paolo Bonzini <pbonzini@redhat.com>, james.hogan@imgtec.com,
        mingo@redhat.com, linux-mips@linux-mips.org, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        David Hildenbrand <dahi@linux.vnet.ibm.com>,
        qemu-ppc@nongnu.org, Cornelia Huck <cornelia.huck@de.ibm.com>,
        Paul Mackerras <paulus@samba.org>,
        David Gibson <david@gibson.dropbear.id.au>
To: Greg Kurz <gkurz@linux.vnet.ibm.com>
Return-path: <linux-mips-bounce@linux-mips.org>
Content-Disposition: inline
In-Reply-To: <20160427054052.Horde.SSxGXKxS_wcijUfLJchjWw2@ltc.linux.ibm.com>
Sender: linux-mips-bounce@linux-mips.org
Errors-to: linux-mips-bounce@linux-mips.org
List-help: <mailto:ecartis@linux-mips.org?Subject=help>
List-unsubscribe: <mailto:ecartis@linux-mips.org?subject=unsubscribe%20linux-mips>
List-software: Ecartis version 1.0.0
List-subscribe: <mailto:ecartis@linux-mips.org?subject=subscribe%20linux-mips>
List-owner: <mailto:ralf@linux-mips.org>
List-post: <mailto:linux-mips@linux-mips.org>
List-archive: <http://www.linux-mips.org/archives/linux-mips/>
List-Id: kvm.vger.kernel.org

2016-04-27 05:40-0400, Gerg Kurz:
> Quoting Greg Kurz <gkurz@linux.vnet.ibm.com>:
> 
>> Commit c896939f7cff ("KVM: use heuristic for fast VCPU lookup by id") added
>> a return path that prevents vcpu ids to exceed KVM_MAX_VCPUS. This is a
>> problem for powerpc where vcpu ids can grow up to 8*KVM_MAX_VCPUS.
>> 
>> This patch simply reverses the logic so that we only try fast path if the
>> vcpu id can be tried as an index in kvm->vcpus[]. The slow path is not
>> affected by the change.
>> 
>> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
>> ---
> 
> Radim,
> 
> I think this sanity check is only needed because kvm_get_vcpu() use the
> id as an index in kvm->vcpus[]. Checking against the new KVM_MAX_VCPU_ID
> would be clearly wrong here.

I agree, checking KVM_MAX_VCPU_ID would be pointless.

> And this patch got two R-b tags already. Do you agree we keep it ?

Yes, thanks.