Re: [PATCH v4 1/1] hw/arm/sbsa-ref: Enable CPU cluster on ARM sbsa machine

[xiongyining1...@phytium.com.cn]

xiongyining1...@phytium.com.cn
 
From: Marcin Juszkiewicz
Date: 2024-05-24 02:47
To: Xiong Yining; qemu-arm; qemu-devel
CC: rad; peter.maydell; quic_llindhol
Subject: Re: [PATCH v4 1/1] hw/arm/sbsa-ref: Enable CPU cluster on ARM sbsa 
machine
W dniu 26.04.2024 o 09:35, Xiong Yining pisze:
> From: xiongyining1480<xiongyining1...@phytium.com.cn>
> 
> Enable CPU cluster support on SbsaQemu platform, so that users can
> specify a 4-level CPU hierarchy sockets/clusters/cores/threads. And
> this topology can be passed to the firmware through DT cpu-map.
> 
> Signed-off-by: Xiong Yining<xiongyining1...@phytium.com.cn>
> tested-by: Marcin Juszkiewicz<marcin.juszkiew...@linaro.org>
 
>I had some thinking about it recently. This patch exported whole 
>/cpus/cpu-map/ tree which we then parse in TF-A to get amount of 
>sockets/clusters/cores/threads.
 
>Why not export them directly? Kind of:
> 
>        cpus {
>                 topology {
>                         threads = <0x01>;
>                         cores = <0x04>;
>                         clusters = <0x01>;
>                         sockets = <0x01>;
>                 };
> 
>It gives everything we need.

Fully agree.
 
>Had some thinking about exporting amount of cores per cluster (8 now, 
>virt uses 16 which is architecture maximum now) in case we would use it 
>in generation of PPTT in EDK2.

I don't fully understand "the amount of cores per cluster", does it means the 
user config: -smp clusters=X, cores=Y which indicates
the number of cores in one cluster is Y, or the AFF0/AFF1 in MPDIR?

The cpu topology is defined by the user on command line which PPTT want to 
align with.  And the value of AFF0/AFF1 is generally 
8 or 16 which will not affected by  option -smp command.   Considering that 
MPDIR cannot reflect the cpu topology configurated by 
user, i guess the PPTT  don't need to use the MPDIR value.