Re: [boot-wrapper v5] aarch64: Start Xen on Armv8-R at EL2

[Mark Rutland <mark.rutland@arm.com>]

On Wed, Nov 27, 2024 at 10:23:00AM +0000, Luca Fancellu wrote:
> When bootwrapper is compiled with Xen support and it is started
> at EL2 on Armv8-R AArch64, keep the current EL and jump to the
> Xen image using the SPSR_KERNEL as spsr_el2 value.
> 
> The only available boot method on Armv8-R AArch64 when starting
> Xen is spin table at the moment, reflect this in the build
> configuration.
> 
> Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
> ---
> v5 changes:
>  - Don't allow AArch64-r + Xen + PSCI from the build system, update the commit
>    message.
> v4 changes:
>  - no changes
> ---
>  Makefile.am         | 1 +
>  arch/aarch64/boot.S | 2 +-
>  configure.ac        | 5 +++++
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile.am b/Makefile.am
> index aecda694fd6c..a8d5c1b96822 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -127,6 +127,7 @@ XEN_CHOSEN	:= xen,xen-bootargs = \"$(XEN_CMDLINE)\";		\
>  			compatible = \"xen,linux-zimage\", \"xen,multiboot-module\"; \
>  			reg = <0x0 $(DOM0_OFFSET) 0x0 $(KERNEL_SIZE)>;	\
>  		   };
> +DEFINES		+= -DXEN
>  endif
>  
>  if INITRD
> diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
> index 565397823cb4..3fcc63bf2437 100644
> --- a/arch/aarch64/boot.S
> +++ b/arch/aarch64/boot.S
> @@ -100,7 +100,7 @@ ASM_FUNC(jump_kernel)
>  	mov	x1, x21
>  	mov	x2, x22
>  	mov	x3, x23
> -#if defined(BOOTWRAPPER_64R)
> +#if defined(BOOTWRAPPER_64R) && !defined(XEN)
>  	// On Armv8-R Linux needs to be booted at EL1
>  	mov	x4, #SPSR_KERNEL_EL1
>  #else
> diff --git a/configure.ac b/configure.ac
> index a433c89bd2ae..a16bc25508f3 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -115,6 +115,11 @@ AS_IF([test "x$USE_PSCI" != "xyes" -a "x$KERNEL_ES" = "x32"],
>  	[AC_MSG_ERROR([With an AArch32 kernel, boot method must be PSCI.])]
>  )
>  
> +# Don't allow PSCI + Xen + aarch64-r
> +AS_IF([test "x$USE_PSCI" = "xyes" -a "x$USE_ARCH" = "xaarch64-r" -a "x$X_IMAGE" != "x"],
> +	[AC_MSG_ERROR([With aarch64-r and Xen, PSCI must be disabled.])]
> +)

I'll delete the comment and change the message here to:

	With an AArch64-R Xen, boot method must be spin-table.

... since that's consistent with the other message above:

	With an AArch32 kernel, boot method must be PSCI.

... and it's slightly nicer to tell the user what will work rather than
what won't work.

Otherwise this looks fine to me, and I will apply this shortly (with
those changes) if no-one objects.

Mark.