From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [kvmarm] [PATCH v5 13/14] KVM: ARM: Handle I/O aborts Date: Mon, 14 Jan 2013 19:00:18 +0000 Message-ID: <20130114190018.GL31341@mudshark.cambridge.arm.com> References: <20130108183811.46302.58543.stgit@ubuntu> <20130108184005.46302.38495.stgit@ubuntu> <20130114164326.GH23505@n2100.arm.linux.org.uk> <20130114184319.GN23505@n2100.arm.linux.org.uk> <20130114185038.GJ31341@mudshark.cambridge.arm.com> <50F4541A.9030702@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Russell King - ARM Linux , "kvm@vger.kernel.org" , Marc Zyngier , Marcelo Tosatti , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" To: Alexander Graf Return-path: Content-Disposition: inline In-Reply-To: <50F4541A.9030702@suse.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: kvm.vger.kernel.org On Mon, Jan 14, 2013 at 06:53:14PM +0000, Alexander Graf wrote: > On 01/14/2013 07:50 PM, Will Deacon wrote: > > FWIW, KVM only needs this code for handling complex MMIO instructions, which > > aren't even generated by recent guest kernels. I'm inclined to suggest removing > > this emulation code from KVM entirely given that it's likely to bitrot as > > it is executed less and less often. > > That'd mean that you heavily limit what type of guests you're executing, > which I don't think is a good idea. To be honest, I don't think we know whether that's true or not. How many guests out there do writeback accesses to MMIO devices? Even on older Linux guests, it was dependent on how GCC felt. I see where you're coming from, I just don't think we can quantify it either way outside of Linux. Will