[PATCH v4 12/15] KVM: arm: keep track of host use of the debug registers

[Zhichao Huang]

Every guest entry, we need to keep track of host use of the debug
registers.

We only call the function upon guest entry, after preempt_disable()
and local_irq_disable(), so there is no race for it.

Signed-off-by: Zhichao Huang <zhichao.huang at linaro.org>
---
 arch/arm/include/asm/kvm_asm.h    | 3 +++
 arch/arm/include/asm/kvm_host.h   | 4 ++++
 arch/arm/kernel/asm-offsets.c     | 1 +
 arch/arm/kvm/arm.c                | 2 ++
 arch/arm/kvm/coproc.c             | 8 ++++++++
 arch/arm64/include/asm/kvm_host.h | 1 +
 6 files changed, 19 insertions(+)

diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h
index 7443a3a..5b1c3eb 100644
--- a/arch/arm/include/asm/kvm_asm.h
+++ b/arch/arm/include/asm/kvm_asm.h
@@ -64,6 +64,9 @@
 #define cp14_DBGDSCRext	65	/* Debug Status and Control external */
 #define NR_CP14_REGS	66	/* Number of regs (incl. invalid) */
 
+#define KVM_ARM_DEBUG_HOST_INUSE_SHIFT	0
+#define KVM_ARM_DEBUG_HOST_INUSE	(1 << KVM_ARM_DEBUG_HOST_INUSE_SHIFT)
+
 #define ARM_EXCEPTION_RESET	  0
 #define ARM_EXCEPTION_UNDEFINED   1
 #define ARM_EXCEPTION_SOFTWARE    2
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index fc461ac..7338f34 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -131,6 +131,9 @@ struct kvm_vcpu_arch {
 	/* System control coprocessor (cp14) */
 	u32 cp14[NR_CP14_REGS];
 
+	/* Debug State */
+	u32 debug_flags;
+
 	/*
 	 * Anything that is not used directly from assembly code goes
 	 * here.
@@ -237,5 +240,6 @@ static inline void kvm_arch_hardware_unsetup(void) {}
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
+void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
 
 #endif /* __ARM_KVM_HOST_H__ */
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index cee4254..7750597 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -178,6 +178,7 @@ int main(void)
   DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
   DEFINE(VCPU_VFP_HOST,		offsetof(struct kvm_cpu_context, vfp));
   DEFINE(VCPU_CP14_HOST,	offsetof(struct kvm_cpu_context, cp14));
+  DEFINE(VCPU_DEBUG_FLAGS,	offsetof(struct kvm_vcpu, arch.debug_flags));
   DEFINE(VCPU_REGS,		offsetof(struct kvm_vcpu, arch.regs));
   DEFINE(VCPU_USR_REGS,		offsetof(struct kvm_vcpu, arch.regs.usr_regs));
   DEFINE(VCPU_SVC_REGS,		offsetof(struct kvm_vcpu, arch.regs.svc_regs));
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index bc738d2..0129346 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -550,6 +550,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 			continue;
 		}
 
+		kvm_arm_setup_debug(vcpu);
+
 		/**************************************************************
 		 * Enter the guest
 		 */
diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index d15b250..b37afd6 100644
--- a/arch/arm/kvm/coproc.c
+++ b/arch/arm/kvm/coproc.c
@@ -1516,3 +1516,11 @@ void kvm_reset_coprocs(struct kvm_vcpu *vcpu)
 		if (vcpu->arch.cp15[num] == 0x42424242)
 			panic("Didn't reset vcpu->arch.cp15[%zi]", num);
 }
+
+void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
+{
+	if (hw_breakpoint_enabled())
+		vcpu->arch.debug_flags |= KVM_ARM_DEBUG_HOST_INUSE;
+	else
+		vcpu->arch.debug_flags &= ~KVM_ARM_DEBUG_HOST_INUSE;
+}
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2709db2..84fa4f0 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -226,5 +226,6 @@ static inline void kvm_arch_hardware_unsetup(void) {}
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
+static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
 
 #endif /* __ARM64_KVM_HOST_H__ */
-- 
1.7.12.4