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Date:   Fri, 22 Feb 2019 14:10:59 +0000
From:   Mark Rutland <mark.rutland@arm.com>
To:     Pintu Agarwal <pintu.ping@gmail.com>
Cc:     open list <linux-kernel@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        linux-riscv@lists.infradead.org, kernelnewbies@kernelnewbies.org
Subject: Re: arm64 Kernel build for qemu-system-aarch64 ?
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On Fri, Feb 22, 2019 at 07:17:00PM +0530, Pintu Agarwal wrote:
> Hi All,

Hi,

> I want to build Linux Kernel 4.20 for arm64 and use it on qemu-arm64.
> I see that there is a defconfig available in arch/arm64/configs/defconfig
> But I am not sure whether it will work for qemu-arm64, and by default
> which machine type is supported.
> 
> I already have working setup for qemu-arm for both versatile and
> vexpress machine. There is already a defconfig available for these
> under arch/arm.
> So I can build the kernel for it.
> 
> But, whether these defconfig are supported for arm64 ?
> If anybody have setup for qemu-arm64 kernel, please share the steps.
> About rootfs, I am planning to use the arm32 version of busybox itself.

The arm64 defconfig is intended to work for all platforms.

I use that with qemu's '-machine virt'. Assuming you use virtio-net and
virtio-block, no additional drivers are required.

For example, I can boot a defconfig kernel using the followign QEMU options:

qemu-system-aarch64 \
        -m 2048 -smp 4 \
        -net nic \
        -net user,host=10.0.2.10,hostfwd=tcp::65022-:22 \
        -nographic \
        -no-reboot \
        -machine virt,accel=kvm,gic_version=host \
        -cpu host \
        -hda ${FILESYSTEM} \
        -snapshot \
        -kernel ${KERNEL} \
        -append "earlycon root=/dev/vda panic_on_warn"

Thanks,
Mark.