[PATCH v3 17/19] arm64: KVM: move hcr_el2 setting into vgic-v2-switch.S

[Christoffer Dall]

On 14 May 2014 15:33, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On Fri, May 09 2014 at  3:07:23 pm BST, Christoffer Dall <christoffer.dall at linaro.org> wrote:
>> On Wed, Apr 16, 2014 at 02:39:49PM +0100, Marc Zyngier wrote:
>>> GICv3 requires the hcr_el2 switch to be tightly coupled with some
>>> of the interrupt controller's register switch.
>>
>> can you be more specific, this feels a bit odd, enabling Stage-2
>> translation and configuring all traps from within the vgic code...
>
> The IMO and FMO bits must be set before restoring the various system
> registers in GICv3. But I agreee that this looks pretty horrible.
>
> The alternative is to split the bits we set in HCR_EL2 into two sets (VM
> and trap control on one side, interrupt control on the other). This
> would translate into two accesses to HCR_EL2, but it would look
> nicer. I'll have a look.
>
>>> In order to have similar code paths, start moving the hcr_el2
>>> manipulation code to the GICv2 switch code.
>>>
>>> Acked-by: Catalin Marinas <catalin.marinas at arm.com>
>>> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
>>> ---
>>>  arch/arm64/kvm/hyp.S            | 7 -------
>>>  arch/arm64/kvm/vgic-v2-switch.S | 8 ++++++++
>>>  2 files changed, 8 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
>>> index aed72d0..92b9120 100644
>>> --- a/arch/arm64/kvm/hyp.S
>>> +++ b/arch/arm64/kvm/hyp.S
>>> @@ -335,11 +335,6 @@
>>>  .endm
>>>
>>>  .macro activate_traps
>>> -    ldr     x2, [x0, #VCPU_IRQ_LINES]
>>> -    ldr     x1, [x0, #VCPU_HCR_EL2]
>>> -    orr     x2, x2, x1
>>> -    msr     hcr_el2, x2
>>> -
>>>      ldr     x2, =(CPTR_EL2_TTA)
>>>      msr     cptr_el2, x2
>>>
>>> @@ -353,8 +348,6 @@
>>>  .endm
>>>
>>>  .macro deactivate_traps
>>> -    mov     x2, #HCR_RW
>>> -    msr     hcr_el2, x2
>>>      msr     cptr_el2, xzr
>>>      msr     hstr_el2, xzr
>>>
>>> diff --git a/arch/arm64/kvm/vgic-v2-switch.S b/arch/arm64/kvm/vgic-v2-switch.S
>>> index c5dc777..d36cd7a 100644
>>> --- a/arch/arm64/kvm/vgic-v2-switch.S
>>> +++ b/arch/arm64/kvm/vgic-v2-switch.S
>>> @@ -85,6 +85,9 @@ CPU_BE(    rev     w5, w5 )
>>>      sub     w4, w4, #1
>>>      cbnz    w4, 1b
>>>  2:
>>> +    mov     x2, #HCR_RW
>>> +    msr     hcr_el2, x2
>>> +    isb
>>>  .endm
>>>
>>>  /*
>>> @@ -92,6 +95,11 @@ CPU_BE(   rev     w5, w5 )
>>>   * x0: Register pointing to VCPU struct
>>>   */
>>>  .macro restore_vgic_v2_state
>>> +    ldr     x2, [x0, #VCPU_IRQ_LINES]
>>
>> will this ever have any values on aarch64?  Don't we mandate vgic
>> support and bail out during hyp init if we cannot init a vgic?
>
> Yes. But that doesn't mean we don't support the feature either. The case
> is fairly slim, I agree, but it has been there since Day-1...
>
See kvm_vm_ioctl_irq_line() in arch/arm/kvm/arm.c:

case KVM_ARM_IRQ_TYPE_CPU:
    if (irqchip_in_kernel(kvm))
        return -ENXIO;

-Christoffer