On 22/02/18 16:02, Christoffer Dall wrote:
> On Thu, Feb 22, 2018 at 03:01:17PM +0000, Marc Zyngier wrote:
>> On Thu, 22 Feb 2018 14:42:27 +0000,
>> Christoffer Dall wrote:
>>>
>>> On Thu, Feb 22, 2018 at 12:32:11PM +0000, Marc Zyngier wrote:
>>>> On 15/02/18 21:03, Christoffer Dall wrote:
>>>>> Just like we can program the GICv2 hypervisor control interface directly
>>>>> from the core vgic code, we can do the same for the GICv3 hypervisor
>>>>> control interface on VHE systems.
>>>>>
>>>>> We do this by simply calling the save/restore functions when we have VHE
>>>>> and we can then get rid of the save/restore function calls from the VHE
>>>>> world switch function.
>>>>>
>>>>> One caveat is that we now write GICv3 system register state before the
>>>>> potential early exit path in the run loop, and because we sync back
>>>>> state in the early exit path, we have to ensure that we read a
>>>>> consistent GIC state from the sync path, even though we have never
>>>>> actually run the guest with the newly written GIC state. We solve this
>>>>> by inserting an ISB in the early exit path.
>>>>>
>>>>> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
>>>>> ---
>>>>>
>>>>> Notes:
>>>>> Changes since v2:
>>>>> - Added ISB in the early exit path in the run loop as explained
>>>>> in the commit message.
>>>>>
>>>>> arch/arm64/kvm/hyp/switch.c | 3 ---
>>>>> virt/kvm/arm/arm.c | 1 +
>>>>> virt/kvm/arm/vgic/vgic.c | 5 +++++
>>>>> 3 files changed, 6 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
>>>>> index cbafc27a617b..466cfcdbcaf3 100644
>>>>> --- a/arch/arm64/kvm/hyp/switch.c
>>>>> +++ b/arch/arm64/kvm/hyp/switch.c
>>>>> @@ -399,8 +399,6 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
>>>>> __activate_traps(vcpu);
>>>>> __activate_vm(vcpu->kvm);
>>>>>
>>>>> - __vgic_restore_state(vcpu);
>>>>> -
>>>>> sysreg_restore_guest_state_vhe(guest_ctxt);
>>>>> __debug_switch_to_guest(vcpu);
>>>>>
>>>>> @@ -414,7 +412,6 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
>>>>> fp_enabled = fpsimd_enabled_vhe();
>>>>>
>>>>> sysreg_save_guest_state_vhe(guest_ctxt);
>>>>> - __vgic_save_state(vcpu);
>>>>>
>>>>> __deactivate_traps(vcpu);
>>>>>
>>>>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
>>>>> index 5bd879c78951..6de7641f3ff2 100644
>>>>> --- a/virt/kvm/arm/arm.c
>>>>> +++ b/virt/kvm/arm/arm.c
>>>>> @@ -717,6 +717,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>>>>> if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
>>>>> kvm_request_pending(vcpu)) {
>>>>> vcpu->mode = OUTSIDE_GUEST_MODE;
>>>>> + isb(); /* Ensure work in x_flush_hwstate is committed */
>>>>> kvm_pmu_sync_hwstate(vcpu);
>>>>> if (static_branch_unlikely(&userspace_irqchip_in_use))
>>>>> kvm_timer_sync_hwstate(vcpu);
>>>>> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
>>>>> index 12e2a28f437e..d0a19a8c196a 100644
>>>>> --- a/virt/kvm/arm/vgic/vgic.c
>>>>> +++ b/virt/kvm/arm/vgic/vgic.c
>>>>> @@ -19,6 +19,7 @@
>>>>> #include <linux/list_sort.h>
>>>>> #include <linux/interrupt.h>
>>>>> #include <linux/irq.h>
>>>>> +#include <asm/kvm_hyp.h>
>>>>>
>>>>> #include "vgic.h"
>>>>>
>>>>> @@ -753,6 +754,8 @@ static inline void vgic_save_state(struct kvm_vcpu *vcpu)
>>>>> {
>>>>> if (!static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif))
>>>>> vgic_v2_save_state(vcpu);
>>>>> + else if (has_vhe())
>>>>> + __vgic_v3_save_state(vcpu);
>>>>> }
>>>>>
>>>>> /* Sync back the hardware VGIC state into our emulation after a guest's run. */
>>>>> @@ -777,6 +780,8 @@ static inline void vgic_restore_state(struct kvm_vcpu *vcpu)
>>>>> {
>>>>> if (!static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif))
>>>>> vgic_v2_restore_state(vcpu);
>>>>> + else if (has_vhe())
>>>>> + __vgic_v3_restore_state(vcpu);
>>>>> }
>>>>>
>>>>> /* Flush our emulation state into the GIC hardware before entering the guest. */
>>>>>
>>>>
>>>> I'm slowly wrapping my brain around this thing again. If I grasp the
>>>> general idea, we end up with two cases:
>>>>
>>>> (1) The GIC is accessible from the kernel, and we save/restore it
>>>> outside of the HYP code.
>>>>
>>>> (2) The GIC is only accessible from the HYP code, and we do it there.
>>>>
>>>> Maybe we should bite the bullet and introduce that primitive instead?
>>>>
>>>
>>> You mean something the following?
>>>
>>> static inline bool can_access_vgic_from_kernel(void)
>>> {
>>> /*
>>> * GICv2 can always be accessed from the kernel because it is
>>> * memory-mapped, and VHE systems can access GICv3 EL2 system
>>> * registers.
>>> */
>>> return !static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif) || has_vhe();
>>> }
>>
>> Yes. I think this would go a long way in making this code easy to
>> understand.
>
> I'll give it a go on the next respin.
>
>> It also mean that we can have a unified save/restore
>> function that picks the right GIC back-end, resulting in less
>> code duplication.
>>
> Not sure I understand hat you mean here?
We now have:
static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)
{
if (static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif)) {
__vgic_v3_activate_traps(vcpu);
__vgic_v3_restore_state(vcpu);
}
}
and
static inline void vgic_restore_state(struct kvm_vcpu *vcpu)
{
if (!static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif))
vgic_v2_restore_state(vcpu);
else if (has_vhe())
__vgic_v3_restore_state(vcpu);
}
I have the feeling that we could reconcile them in a nice way, but
I'm not completely sure now...
M.
--
Jazz is not dead. It just smells funny...
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