diff options
author | Christoffer Dall <cdall@cs.columbia.edu> | 2012-02-23 00:11:57 -0500 |
---|---|---|
committer | Marc Zyngier <marc.zyngier@arm.com> | 2012-07-23 14:08:34 +0100 |
commit | 0658df91d21a8c2df82e6ef36177ac8c7007c8b3 (patch) | |
tree | ae19e8186e2c0100c2d1751f1a1e5451547b806b | |
parent | 2b743ecc7f098c02a8c3fe40dabc8ee173c800df (diff) | |
download | linux-kvm-arm-kvm-a15-v10-stage-v3.5.tar.gz |
ARM: KVM: Guest wait-for-interrupts (WFI) supportkvm-a15-v10-stage-v3.5
When the guest executes a WFI instruction the operation is trapped to
KVM, which emulates the instruction in software. There is no correlation
between a guest executing a WFI instruction and actually putting the
hardware into a low-power mode, since a KVM guest is essentially a
process and the WFI instruction can be seen as 'sleep' call from this
process. Therefore, we flag the VCPU to be in wait_for_interrupts mode
and call the main KVM function kvm_vcpu_block() function. This function
will put the thread on a wait-queue and call schedule.
When an interrupt comes in through KVM_IRQ_LINE (see previous patch) we
signal the VCPU thread and unflag the VCPU to no longer wait for
interrupts. All calls to kvm_arch_vcpu_ioctl_run() result in a call to
kvm_vcpu_block() as long as the VCPU is in wfi-mode.
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
-rw-r--r-- | arch/arm/kvm/arm.c | 15 | ||||
-rw-r--r-- | arch/arm/kvm/emulate.c | 12 | ||||
-rw-r--r-- | arch/arm/kvm/trace.h | 16 |
3 files changed, 42 insertions, 1 deletions
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c index b18f68fafa004..f3b206ac1fe55 100644 --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -306,9 +306,17 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu, return -EINVAL; } +/** + * kvm_arch_vcpu_runnable - determine if the vcpu can be scheduled + * @v: The VCPU pointer + * + * If the guest CPU is not waiting for interrupts (or waiting and + * an interrupt is pending) then it is by definition runnable. + */ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) { - return 0; + return !!v->arch.irq_lines || + !v->arch.wait_for_interrupts; } int kvm_arch_vcpu_in_guest_mode(struct kvm_vcpu *v) @@ -538,6 +546,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) */ cond_resched(); + if (vcpu->arch.wait_for_interrupts) + kvm_vcpu_block(vcpu); + update_vttbr(vcpu->kvm); /* @@ -635,6 +646,8 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level) * trigger a world-switch round on the running physical CPU to set the * virtual IRQ/FIQ fields in the HCR appropriately. */ + if (irq_level->level) + vcpu->arch.wait_for_interrupts = 0; kvm_vcpu_kick(vcpu); return 0; diff --git a/arch/arm/kvm/emulate.c b/arch/arm/kvm/emulate.c index 99432d83006fb..564add20f2e02 100644 --- a/arch/arm/kvm/emulate.c +++ b/arch/arm/kvm/emulate.c @@ -505,9 +505,21 @@ int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run) return emulate_cp15(vcpu, ¶ms); } +/** + * kvm_handle_wfi - handle a wait-for-interrupts instruction executed by a guest + * @vcpu: the vcpu pointer + * @run: the kvm_run structure pointer + * + * Simply sets the wait_for_interrupts flag on the vcpu structure, which will + * halt execution of world-switches and schedule other host processes until + * there is an incoming IRQ or FIQ to the VM. + */ int kvm_handle_wfi(struct kvm_vcpu *vcpu, struct kvm_run *run) { + trace_kvm_wfi(vcpu->arch.regs.pc); vcpu->stat.wfi_exits++; + if (!vcpu->arch.irq_lines) + vcpu->arch.wait_for_interrupts = 1; return 0; } diff --git a/arch/arm/kvm/trace.h b/arch/arm/kvm/trace.h index 325106c8f88c4..28ed1a18b289e 100644 --- a/arch/arm/kvm/trace.h +++ b/arch/arm/kvm/trace.h @@ -90,6 +90,22 @@ TRACE_EVENT(kvm_emulate_cp15_imp, __entry->CRm, __entry->Op2) ); +TRACE_EVENT(kvm_wfi, + TP_PROTO(unsigned long vcpu_pc), + TP_ARGS(vcpu_pc), + + TP_STRUCT__entry( + __field( unsigned long, vcpu_pc ) + ), + + TP_fast_assign( + __entry->vcpu_pc = vcpu_pc; + ), + + TP_printk("guest executed wfi at: 0x%08lx", __entry->vcpu_pc) +); + + #endif /* _TRACE_KVM_H */ #undef TRACE_INCLUDE_PATH |