From mboxrd@z Thu Jan 1 00:00:00 1970 From: gavin.guo@canonical.com (Gavin Guo) Date: Mon, 7 Oct 2013 17:17:01 +0800 Subject: [PATCH 3/3] KVM: ARM: Add support for Cortex-A7 In-Reply-To: <52526BDC.3050305@arm.com> References: <1380210568-23175-1-git-send-email-jonathan.austin@arm.com> <1380210568-23175-4-git-send-email-jonathan.austin@arm.com> <20130926161743.GD1389@cbox> <52446A48.9070501@arm.com> <52526BDC.3050305@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Oct 7, 2013 at 4:07 PM, Marc Zyngier wrote: > > On 07/10/13 07:16, Gavin Guo wrote: > > On Sun, Oct 6, 2013 at 10:56 PM, Peter Maydell > > wrote: > > > > On 6 October 2013 23:03, Gavin Guo > > wrote: > > > Does it mean the currently qemu can't support A15 vcpu running on > > host A7? > > > > No, that's a kernel restriction. That is why the patch description > > reads: > > # This patch adds support for running Cortex-A7 guests on Cortex-A7 > > hosts. > > > > (What QEMU is currently missing is A7 support, so you can't ask it to > > run an A7 guest CPU.) > > > > -- PMM > > > > > > Thanks, I saw the checking in the kvm_vcpu_set_target(). I'm confused > > that what is the concern to run the same cpu type? Does it matter to run > > A15 on A7 or inverse? > > It does. MIDR registers are different. Cache size is different. It may > work, or it may not. And at the very least, you should present a > consistent view of the underlying system to the unsuspecting OS. > > M. > -- > Jazz is not dead. It just smells funny... > Hi Marc, How about the guest os with 4 x A15 vcpus run on a TC2 with 5 cores enabled (2 x A15 + 3 x A7). Does it mean that the 4 x A15 vcpus need to run on the 2 x A15 real cpus and can't be migrate to the 3 x A7? It seems that running 4 x A15 vcpus on the 2 x A15 and 2 x A7 core and leaving 1 A7 idle can take more computing power if all of the 4 x A15 guest os vcpus are full of loading. BTW, thanks for your reply, according to your reply I know the MIDR and cache size are different. Furthermore, I'd like to know if it is possible to make vcpu and real cpu in different type? If yes, I would like to study how to modify to make it work. Thanks, Gavin