From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [RFC PATCH 17/17] KVM: PPC: Add an ioctl for userspace to select which platform to emulate Date: Fri, 01 Jul 2011 09:13:12 +1000 Message-ID: <1309475592.14501.211.camel@pasglop> References: <20110629101552.GA25406@bloggs.ozlabs.ibm.com> <20110629104103.GR25406@bloggs.ozlabs.ibm.com> <4E0C9077.2060608@suse.de> <4E0C9339.2080601@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Alexander Graf , Scott Wood , linuxppc-dev@ozlabs.org, Paul Mackerras , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org To: Avi Kivity Return-path: In-Reply-To: <4E0C9339.2080601@redhat.com> Sender: kvm-ppc-owner@vger.kernel.org List-Id: kvm.vger.kernel.org > Regarding that. There's another option - the ioctl code embeds the > structure size. So if we extend the ioctl parsing to pad up (or > truncate down) from the user's size to our size, and similarly in the > other direction, we can get away from this ugliness. I don't like relying on that much ... I prefer having an explicit version in the structure head (or use a flag). > Some years ago I posted a generic helper that did this (and also > kmalloc'ed and kfree'd the data itself), but it wasn't received > favourably. Maybe I should try again (and we can possibly use it in kvm > even if it is rejected for general use, though that's against our > principles of pushing all generic infrastructure to the wider kernel). Cheers, Ben.