On 07/05/2015 12:34 PM, Christoffer Dall wrote:
> On Wed, Jun 24, 2015 at 08:30:27PM -0700, Mario Smarduch wrote:
>> This patch implements the VFP context switch code called from vcpu_put in
>> Host KVM. In addition it implements the logic to skip setting a VFP trap if
>> one
>> is not needed. Also resets the flag if Host KVM switched registers to trap
>> new
>> guest vfp accesses.
>>
>>
>> Signed-off-by: Mario Smarduch <m.smard...@samsung.com>
>> ---
>> arch/arm/kvm/interrupts.S | 49
>> ++++++++++++++++++++++++++++-----------------
>> 1 file changed, 31 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
>> index 79caf79..0912edd 100644
>> --- a/arch/arm/kvm/interrupts.S
>> +++ b/arch/arm/kvm/interrupts.S
>> @@ -96,6 +96,21 @@ ENTRY(__kvm_flush_vm_context)
>> bx lr
>> ENDPROC(__kvm_flush_vm_context)
>>
>> +ENTRY(__kvm_restore_host_vfp_state)
>> + push {r3-r7}
>> +
>> + mov r1, #0
>> + str r1, [r0, #VCPU_VFP_SAVED]
>> +
>> + add r7, r0, #VCPU_VFP_GUEST
>> + store_vfp_state r7
>> + add r7, r0, #VCPU_VFP_HOST
>> + ldr r7, [r7]
>> + restore_vfp_state r7
>> +
>> + pop {r3-r7}
>> + bx lr
>> +ENDPROC(__kvm_restore_host_vfp_state)
>
> it feels a bit strange to introduce this function here when I cannot see
> how it's called.
>
> At the very least, could you provide the C equivalent prototype in a
> comment or specify what the input registers are? E.g.
Yes again that's on a todo list.
>
> /*
> * void __kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu);
> */
>
>>
>> /********************************************************************
>> * Hypervisor world-switch code
>> @@ -131,7 +146,13 @@ ENTRY(__kvm_vcpu_run)
>>
>> @ Trap coprocessor CRx accesses
>> set_hstr vmentry
>> +
>> + ldr r1, [vcpu, #VCPU_VFP_SAVED]
>> + cmp r1, #1
>> + beq skip_guest_vfp_trap
>> set_hcptr vmentry, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
>> +skip_guest_vfp_trap:
>> +
>> set_hdcr vmentry
>>
>> @ Write configured ID register into MIDR alias
>> @@ -173,18 +194,6 @@ __kvm_vcpu_return:
>> set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
>>
>> #ifdef CONFIG_VFPv3
>> - @ Save floating point registers we if let guest use them.
>> - tst r2, #(HCPTR_TCP(10) | HCPTR_TCP(11))
>> - bne after_vfp_restore
>> -
>> - @ Switch VFP/NEON hardware state to the host's
>> - add r7, vcpu, #VCPU_VFP_GUEST
>> - store_vfp_state r7
>> - add r7, vcpu, #VCPU_VFP_HOST
>> - ldr r7, [r7]
>> - restore_vfp_state r7
>> -
>> -after_vfp_restore:
>> @ Restore FPEXC_EN which we clobbered on entry
>> pop {r2}
>> VFPFMXR FPEXC, r2
>> @@ -363,10 +372,6 @@ 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.
>>
>> @@ -380,7 +385,10 @@ hyp_hvc:
>> cmp r2, #0
>> bne guest_trap @ Guest called HVC
>>
>> -host_switch_to_hyp:
>> + /*
>> + * Getting here means host called HVC, we shift parameters and branch
>> + * to Hyp function.
>> + */
>
> not sure this comment change belongs in this patch (but the comment is
> well-written).
I built this patch on top of previous one. But IMO this series
is not ready for upstream yet.
>
>> pop {r0, r1, r2}
>>
>> /* Check for __hyp_get_vectors */
>> @@ -411,6 +419,10 @@ guest_trap:
>>
>> @ Check if we need the fault information
>> lsr r1, r1, #HSR_EC_SHIFT
>> +#ifdef CONFIG_VFPv3
>> + cmp r1, #HSR_EC_CP_0_13
>> + beq switch_to_guest_vfp
>> +#endif
>> cmp r1, #HSR_EC_IABT
>> mrceq p15, 4, r2, c6, c0, 2 @ HIFAR
>> beq 2f
>> @@ -479,11 +491,12 @@ guest_trap:
>> */
>> #ifdef CONFIG_VFPv3
>> switch_to_guest_vfp:
>> - load_vcpu @ Load VCPU pointer to r0
>> push {r3-r7}
>>
>> @ NEON/VFP used. Turn on VFP access.
>> set_hcptr vmexit, (HCPTR_TCP(10) | HCPTR_TCP(11))
>> + mov r1, #1
>> + str r1, [vcpu, #VCPU_VFP_SAVED]
>>
>> @ Switch VFP/NEON hardware state to the guest's
>> add r7, r0, #VCPU_VFP_HOST
>> --
>> 1.7.9.5
>>
> It would probably be easier to just rebase this on the previous series
> and refer to that in the cover letter, but the approach here looks
> otherwise right to me.
What if we used the simplified approach (as Marc mentioned) and
let it run for quite a while and then move this series?
>
> -Christoffer
>
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