Re: [PATCH v3 03/52] xen/arm: add an option to define Xen start address for Armv8-R

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

Hi Penny,

On 26/06/2023 04:33, Penny Zheng wrote:
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>
> From: Wei Chen <wei.chen@xxxxxxx>
>
> On Armv8-A, Xen has a fixed virtual start address (link address
> too) for all Armv8-A platforms. In an MMU based system, Xen can
> map its loaded address to this virtual start address. So, on
> Armv8-A platforms, the Xen start address does not need to be
> configurable. But on Armv8-R platforms, there is no MMU to map
> loaded address to a fixed virtual address and different platforms
> will have very different address space layout. So Xen cannot use
> a fixed physical address on MPU based system and need to have it
> configurable.
>
> In this patch we introduce one Kconfig option for users to define
> the default Xen start address for Armv8-R. Users can enter the
> address in config time, or select the tailored platform config
> file from arch/arm/configs.
>
> And as we introduced Armv8-R to Xen, that means the existed Arm64
> MMU based platforms should not be listed in Armv8-R platform
> list, so we add !HAS_MPU dependency for these platforms.
>
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> ---
> v1 -> v2:
> 1. Remove the platform header fvp_baser.h.
> 2. Remove the default start address for fvp_baser64.
> 3. Remove the description of default address from commit log.
> 4. Change HAS_MPU to ARM_V8R for Xen start address dependency.
>     No matter Arm-v8r board has MPU or not, it always need to
>     specify the start address.
> ---
> v3:
> 1. Remove unrelated change of "CONFIG_FVP_BASER"
> 2. Change ARM_V8R to HAS_MPU for Xen start address dependency
> ---
>   xen/arch/arm/Kconfig           | 8 ++++++++
>   xen/arch/arm/platforms/Kconfig | 8 +++++---
>   2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index 70fdc2ba63..ff17345cdb 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -181,6 +181,14 @@ config TEE
>            This option enables generic TEE mediators support. It allows guests
>            to access real TEE via one of TEE mediators implemented in XEN.
>
> +config XEN_START_ADDRESS
> +       hex "Xen start address: keep default to use platform defined address"
> +       default 0
> +       depends on HAS_MPU
> +       help
> +         This option allows to set the customized address at which Xen will be
> +         linked on MPU systems. This address must be aligned to a page size.
> +
>   source "arch/arm/tee/Kconfig"
>
>   config STATIC_SHM
> diff --git a/xen/arch/arm/platforms/Kconfig b/xen/arch/arm/platforms/Kconfig
> index c93a6b2756..75af48b5f9 100644
> --- a/xen/arch/arm/platforms/Kconfig
> +++ b/xen/arch/arm/platforms/Kconfig
> @@ -1,6 +1,7 @@
>   choice
>          prompt "Platform Support"
>          default ALL_PLAT
> +       default NO_PLAT if HAS_MPU
I am a bit concerned about this as we will be introducing R52 specific 
platform in xen/arch/arm/platforms/
(For eg 
https://github.com/Xilinx/xen/blob/xlnx_rebase_4.17/xen/arch/arm_mpu/platforms/amd-versal-net.c 
)
Thus, we will have to remove this line at that time.

Can you remove this line, please if it does not cause any issue ?

- Ayan

>          ---help---
>          Choose which hardware platform to enable in Xen.
>
> @@ -8,13 +9,14 @@ choice
>
>   config ALL_PLAT
>          bool "All Platforms"
> +       depends on !HAS_MPU
>          ---help---
>          Enable support for all available hardware platforms. It doesn't
>          automatically select any of the related drivers.
>
>   config QEMU
>          bool "QEMU aarch virt machine support"
> -       depends on ARM_64
> +       depends on ARM_64 && !HAS_MPU
>          select GICV3
>          select HAS_PL011
>          ---help---
> @@ -23,7 +25,7 @@ config QEMU
>
>   config RCAR3
>          bool "Renesas RCar3 support"
> -       depends on ARM_64
> +       depends on ARM_64 && !HAS_MPU
>          select HAS_SCIF
>          select IPMMU_VMSA
>          ---help---
> @@ -31,7 +33,7 @@ config RCAR3
>
>   config MPSOC
>          bool "Xilinx Ultrascale+ MPSoC support"
> -       depends on ARM_64
> +       depends on ARM_64 && !HAS_MPU
>          select HAS_CADENCE_UART
>          select ARM_SMMU
>          ---help---
> --
> 2.25.1