Date: Wed, 27 Apr 2016 16:40:14 +0200
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
To: Greg Kurz <gkurz@linux.vnet.ibm.com>
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>
Subject: Re: [PATCH v4 1/2] KVM: remove NULL return path for vcpu ids >=
 KVM_MAX_VCPUS
Message-ID: <20160427144010.GA27247@potion>
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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.