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Re: [Qemu-devel] [PATCH] Fix default CPU model for ARM64

From: Pavel Fedin
Subject: Re: [Qemu-devel] [PATCH] Fix default CPU model for ARM64
Date: Thu, 07 May 2015 09:36:59 +0300


> Yes. qemu-system-aarch64 -cpu cortex-a15 gets you a 32-bit Cortex-A15. This is
> exactly like the x86 QEMU, where you can emulate all the 32-bit x86 CPUs in
> qemu-system-x86_64.

 And what is the default in x86_64 ? I believe it's 64-bit CPU, and not i686, 
isn't it ?
 I agree that -cpu cortex-a15 might work with qemu-system-aarch64. But isn't it 
expected to get the "native" CPU by default ? This behavior of qemu causes 
weird thing with libvirt/virt-manager. I create a VM, specify "aarch64" as 
architecture, and set "hypervisor default" as CPU model. With "hypervisor 
default" libvirt does not pass any -cpu option to qemu, leaving it up to the 
emulator (exactly as expected). So, i supply 64-bit kernel and rootfs, and 
nothing works. I have to explicitly change the CPU to "cortex-a57". Isn't it 
confusing to have such a default ?
 This is even more confusing since currently i don't know any implementation of 
aarch64 except A57 and A53 (which are the same from software point of view). 
So, i believe, A57 is quite a reasonable default.

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia

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