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Re: [PATCH 5/5] xen: arm64: remove -mgeneral-regs-only for vfp.c
- To: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 29 Nov 2024 09:12:52 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 29 Nov 2024 08:13:00 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 29.11.2024 02:49, Volodymyr Babchuk wrote:
> vfp.c actually accesses VFP registers, so it can't be built with
> -mgeneral-regs-only flag when using clang, as clang will complain
> about this:
>
> arch/arm/arm64/vfp.c:9:18: error: instruction requires: fp-armv8
> 9 | asm volatile("stp q0, q1, [%1, #16 * 0]\n\t"
> |
Imo this needs addressing by inserting appropriate .arch_extension directives
in the asm(), to limit the scope of where VFP registers can be used to _just_
where we want them used.
> --- a/xen/arch/arm/arm64/Makefile
> +++ b/xen/arch/arm/arm64/Makefile
> @@ -18,3 +18,5 @@ obj-$(CONFIG_ARM64_SVE) += sve.o sve-asm.o
> obj-y += traps.o
> obj-y += vfp.o
> obj-y += vsysreg.o
> +
> +$(obj)/vfp.o: CFLAGS_REMOVE += -mgeneral-regs-only
This, after all, allows the compiler to also use them behind our backs.
Jan
|
