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

[Luca Fancellu]

Hi Mark,

> On 28 Nov 2024, at 11:03, Mark Rutland <mark.rutland at arm.com> wrote:
> 
> 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 at 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.

Sounds good to me! Thanks!

> 
> Mark.