linux/include/kvm/arm_arch_timer.h, branch v4.15

KVM: arm/arm64: timer: Don't set irq as forwarded if no usable GIC

2017-12-18T09:53:23Z

If we don't have a usable GIC, do not try to set the vcpu affinity as this is guaranteed to fail. Reported-by: Andre Przywara Reviewed-by: Andre Przywara Tested-by: Andre Przywara Reviewed-by: Christoffer Dall Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall

KVM: arm/arm64: Don't enable/disable physical timer access on VHE

2017-11-29T15:46:09Z

After the timer optimization rework we accidentally end up calling physical timer enable/disable functions on VHE systems, which is neither needed nor correct, since the CNTHCTL_EL2 register format is different when HCR_EL2.E2H is set. The CNTHCTL_EL2 is initialized when CPUs become online in kvm_timer_init_vhe() and we don't have to call these functions on VHE systems, which also allows us to inline the non-VHE functionality. Reported-by: Jintack Lim Signed-off-by: Christoffer Dall

KVM: arm/arm64: Rework kvm_timer_should_fire

2017-11-06T15:23:17Z

kvm_timer_should_fire() can be called in two different situations from the kvm_vcpu_block(). The first case is before calling kvm_timer_schedule(), used for wait polling, and in this case the VCPU thread is running and the timer state is loaded onto the hardware so all we have to do is check if the virtual interrupt lines are asserted, becasue the timer interrupt handler functions will raise those lines as appropriate. The second case is inside the wait loop of kvm_vcpu_block(), where we have already called kvm_timer_schedule() and therefore the hardware will be disabled and the software view of the timer state is up to date (timer->loaded is false), and so we can simply check if the timer should fire by looking at the software state. Signed-off-by: Christoffer Dall Reviewed-by: Marc Zyngier

KVM: arm/arm64: Get rid of kvm_timer_flush_hwstate

2017-11-06T15:23:16Z

Now when both the vtimer and the ptimer when using both the in-kernel vgic emulation and a userspace IRQ chip are driven by the timer signals and at the vcpu load/put boundaries, instead of recomputing the timer state at every entry/exit to/from the guest, we can get entirely rid of the flush hwstate function. Signed-off-by: Christoffer Dall Acked-by: Marc Zyngier

KVM: arm/arm64: Avoid timer save/restore in vcpu entry/exit

2017-11-06T15:23:14Z

We don't need to save and restore the hardware timer state and examine if it generates interrupts on on every entry/exit to the guest. The timer hardware is perfectly capable of telling us when it has expired by signaling interrupts. When taking a vtimer interrupt in the host, we don't want to mess with the timer configuration, we just want to forward the physical interrupt to the guest as a virtual interrupt. We can use the split priority drop and deactivate feature of the GIC to do this, which leaves an EOI'ed interrupt active on the physical distributor, making sure we don't keep taking timer interrupts which would prevent the guest from running. We can then forward the physical interrupt to the VM using the HW bit in the LR of the GIC, like we do already, which lets the guest directly deactivate both the physical and virtual timer simultaneously, allowing the timer hardware to exit the VM and generate a new physical interrupt when the timer output is again asserted later on. We do need to capture this state when migrating VCPUs between physical CPUs, however, which we use the vcpu put/load functions for, which are called through preempt notifiers whenever the thread is scheduled away from the CPU or called directly if we return from the ioctl to userspace. One caveat is that we have to save and restore the timer state in both kvm_timer_vcpu_[put/load] and kvm_timer_[schedule/unschedule], because we can have the following flows: 1. kvm_vcpu_block 2. kvm_timer_schedule 3. schedule 4. kvm_timer_vcpu_put (preempt notifier) 5. schedule (vcpu thread gets scheduled back) 6. kvm_timer_vcpu_load (preempt notifier) 7. kvm_timer_unschedule And a version where we don't actually call schedule: 1. kvm_vcpu_block 2. kvm_timer_schedule 7. kvm_timer_unschedule Since kvm_timer_[schedule/unschedule] may not be followed by put/load, but put/load also may be called independently, we call the timer save/restore functions from both paths. Since they rely on the loaded flag to never save/restore when unnecessary, this doesn't cause any harm, and we ensure that all invokations of either set of functions work as intended. An added benefit beyond not having to read and write the timer sysregs on every entry and exit is that we no longer have to actively write the active state to the physical distributor, because we configured the irq for the vtimer to only get a priority drop when handling the interrupt in the GIC driver (we called irq_set_vcpu_affinity()), and the interrupt stays active after firing on the host. Reviewed-by: Marc Zyngier Signed-off-by: Christoffer Dall

KVM: arm/arm64: Use separate timer for phys timer emulation

2017-11-06T15:23:12Z

We were using the same hrtimer for emulating the physical timer and for making sure a blocking VCPU thread would be eventually woken up. That worked fine in the previous arch timer design, but as we are about to actually use the soft timer expire function for the physical timer emulation, change the logic to use a dedicated hrtimer. This has the added benefit of not having to cancel any work in the sync path, which in turn allows us to run the flush and sync with IRQs disabled. Note that the hrtimer used to program the host kernel's timer to generate an exit from the guest when the emulated physical timer fires never has to inject any work, and to share the soft_timer_cancel() function with the bg_timer, we change the function to only cancel any pending work if the pointer to the work struct is not null. Acked-by: Marc Zyngier Signed-off-by: Christoffer Dall

KVM: arm/arm64: Rename soft timer to bg_timer

2017-11-06T15:23:11Z

As we are about to introduce a separate hrtimer for the physical timer, call this timer bg_timer, because we refer to this timer as the background timer in the code and comments elsewhere. Signed-off-by: Christoffer Dall Acked-by: Marc Zyngier

KVM: arm/arm64: Make timer_arm and timer_disarm helpers more generic

2017-11-06T15:23:11Z

We are about to add an additional soft timer to the arch timer state for a VCPU and would like to be able to reuse the functions to program and cancel a timer, so we make them slightly more generic and rename to make it more clear that these functions work on soft timers and not the hardware resource that this code is managing. The armed flag on the timer state is only used to assert a condition, and we don't rely on this assertion in any meaningful way, so we can simply get rid of this flack and slightly reduce complexity. Acked-by: Marc Zyngier Signed-off-by: Christoffer Dall

KVM: arm/arm64: Allow setting the timer IRQ numbers from userspace

2017-06-08T14:59:57Z

First we define an ABI using the vcpu devices that lets userspace set the interrupt numbers for the various timers on both the 32-bit and 64-bit KVM/ARM implementations. Second, we add the definitions for the groups and attributes introduced by the above ABI. (We add the PMU define on the 32-bit side as well for symmetry and it may get used some day.) Third, we set up the arch-specific vcpu device operation handlers to call into the timer code for anything related to the KVM_ARM_VCPU_TIMER_CTRL group. Fourth, we implement support for getting and setting the timer interrupt numbers using the above defined ABI in the arch timer code. Fifth, we introduce error checking upon enabling the arch timer (which is called when first running a VCPU) to check that all VCPUs are configured to use the same PPI for the timer (as mandated by the architecture) and that the virtual and physical timers are not configured to use the same IRQ number. Signed-off-by: Christoffer Dall Reviewed-by: Marc Zyngier

KVM: arm/arm64: Move timer IRQ default init to arch_timer.c

2017-06-08T14:59:56Z

We currently initialize the arch timer IRQ numbers from the reset code, presumably because we once intended to model multiple CPU or SoC types from within the kernel and have hard-coded reset values in the reset code. As we are moving towards userspace being in charge of more fine-grained CPU emulation and stitching together the pieces needed to emulate a particular type of CPU, we should no longer have a tight coupling between resetting a VCPU and setting IRQ numbers. Therefore, move the logic to define and use the default IRQ numbers to the timer code and set the IRQ number immediately when creating the VCPU. Signed-off-by: Christoffer Dall Reviewed-by: Marc Zyngier