Re: [OE-core] [PATCH] qemuarm64: maximise the emulated CPU capabilities

[Mikko Rapeli <mikko.rapeli@linaro.org>]

Hi,

On Tue, Feb 13, 2024 at 04:42:23PM +0000, Ross Burton wrote:
> From: Ross Burton <ross.burton@arm.com>
> 
> Instead of emulating a Cortex-A57, just ask qemu to emulate everything
> it knows how to (apart from Pointer Authentication, where we use qemu's
> implementation-defined algorithm which is vastly faster to emulate).
> 
> This does not change the tune, so the generated code is identical. The
> advantage of doing this is that it lets us verify that features such as
> Branch Target Indentification, which requires hardware support, is
> actually functional.
> 
> Signed-off-by: Ross Burton <ross.burton@arm.com>
> ---
>  meta/conf/machine/qemuarm64.conf | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/meta/conf/machine/qemuarm64.conf b/meta/conf/machine/qemuarm64.conf
> index a096d964db5..63af4cd346d 100644
> --- a/meta/conf/machine/qemuarm64.conf
> +++ b/meta/conf/machine/qemuarm64.conf
> @@ -14,7 +14,7 @@ SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"
>  # For runqemu
>  QB_SYSTEM_NAME = "qemu-system-aarch64"
>  QB_MACHINE = "-machine virt"
> -QB_CPU = "-cpu cortex-a57"
> +QB_CPU = "-cpu max,pauth-impdef=on"

FWIW, this can also be risky and cause instabilities. We've seen boot hangs
at least with old qemu 7.2 and kernel 4.xy where serial console detection
did not correctly work on every boot.

If things work now, then great!

Cheers,

-Mikko