Re: [PATCH v2 2/2] arm: KVM: keep arm vfp/simd exit handling consistent with arm64

[Marc Zyngier <marc.zyngier@arm.com>]

On 16/06/15 22:50, Mario Smarduch wrote:
> After enhancing arm64 FP/SIMD exit handling, FP/SIMD exit branch is moved
> to guest trap handling. This keeps exiting handling flow between both
> architectures consistent.
> 
> Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>
> ---
>  arch/arm/kvm/interrupts.S |   12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index 79caf79..fca2c56 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -363,10 +363,6 @@ hyp_hvc:
>  	@ Check syndrome register
>  	mrc	p15, 4, r1, c5, c2, 0	@ HSR
>  	lsr	r0, r1, #HSR_EC_SHIFT
> -#ifdef CONFIG_VFPv3
> -	cmp	r0, #HSR_EC_CP_0_13
> -	beq	switch_to_guest_vfp
> -#endif
>  	cmp	r0, #HSR_EC_HVC
>  	bne	guest_trap		@ Not HVC instr.
>  
> @@ -406,6 +402,12 @@ THUMB(	orr	lr, #1)
>  1:	eret
>  
>  guest_trap:
> +#ifdef CONFIG_VFPv3
> +	/* Guest accessed VFP/SIMD registers, save host, restore Guest */
> +	cmp	r0, #HSR_EC_CP_0_13
> +	beq	switch_to_guest_fpsimd
> +#endif
> +
>  	load_vcpu			@ Load VCPU pointer to r0
>  	str	r1, [vcpu, #VCPU_HSR]
>  
> @@ -478,7 +480,7 @@ guest_trap:
>   * inject an undefined exception to the guest.
>   */
>  #ifdef CONFIG_VFPv3
> -switch_to_guest_vfp:
> +switch_to_guest_fpsimd:

Ah, I think I managed to confuse you in my previous comment.
On ARMv7, we call the floating point stuff VFP.
On ARMv8, we call it FP/SIMD.

Not very consistent, I know...

>  	load_vcpu			@ Load VCPU pointer to r0

It would be interesting to find out if we can make this load_vcpu part
of the common sequence (without spilling another register, of course).
Probably involves moving the exception class to r2.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...