Subject: [PATCH] arm64: KVM: Turn kvm_ksym_ref into a NOP on VHE

From: [email-masked] (Robin Murphy)
Date: Fri, 18 Mar 2016 17:41:19 +0000

Hi Marc,

On 18/03/16 17:25, Marc Zyngier wrote:
> When running with VHE, there is no need to translate kernel pointers
> to the EL2 memory space, since we're already there (and we have a much
> saner memory map to start with).
>
> Unfortunately, kvm_ksym_ref is getting in the way, and the first
> call into the "hypervisor" section is going to end up in fireworks,
> since we're now branching into nowhereland. Meh.
>
> A potential solution is to test if VHE is engaged or not, and only
> perform the translation in the negative case. With this in place,
> VHE is able to run again.
>
> Signed-off-by: Marc Zyngier <[email-masked]>
> ---
>   arch/arm64/include/asm/kvm_asm.h | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 226f49d..282f907 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -26,7 +26,13 @@
>   #define KVM_ARM64_DEBUG_DIRTY_SHIFT	0
>   #define KVM_ARM64_DEBUG_DIRTY		(1 << KVM_ARM64_DEBUG_DIRTY_SHIFT)
>
> -#define kvm_ksym_ref(sym)		phys_to_virt((u64)&sym - kimage_voffset)
> +#define kvm_ksym_ref(sym)						\
> +	({								\
> +		void *val = sym;					\
> +		if (!is_kernel_in_hyp_mode())				\
> +			val = phys_to_virt((u64)&sym - kimage_voffset);	\

Is it definitely OK to evaluate sym twice here?

Robin.

> +		val;							\
> +	 })
>   #ifndef __ASSEMBLY__
>   struct kvm;