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

From: [email-masked] (Marc Zyngier)
Date: Fri, 19 Jun 2015 14:50:33 +0100

On 19/06/15 00:49, Mario Smarduch wrote:
> On 06/18/2015 10:27 AM, Marc Zyngier wrote:
>> 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 <[email-masked]>
>>> ---
>>>  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.
> 
> Ah I see, I'll update.
>>
>> Not very consistent, I know...
>>
>>>  	load_vcpu			@ Load VCPU pointer to r0
> 
> How about move it here - then it does not stick out like
> before.
> 
> guest_trap:
>         load_vcpu                       @ Load VCPU pointer to r0
>         str     r1, [vcpu, #VCPU_HSR]
> 
>         @ Check if we need the fault information
>         lsr     r1, r1, #HSR_EC_SHIFT
> #ifdef CONFIG_VFPv3
>         /* Guest accessed VFP/SIMD registers, save host, restore Guest */
>         cmp     r1, #HSR_EC_CP_0_13
>         beq     switch_to_guest_vfp
> #endif

That would work.

> Regarding "host_switch_to_hyp:" it has no reference but appears
> like a clean separator, that's on purpose?

Not really. It looks like a leftover from the original HYP calling
method that we used to have, before the code got merged.

You could replace it by a simple comment saying that from this point on,
we're dealing with a HVC call from the host.

Thanks,

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