[PATCH 06/15] KVM: arm64: Advance debug_owner state machine for sysreg traps

[Oliver Upton <oliver.upton@linux.dev>]

Preserve lazy restore of the breakpoint/watchpoint registers by updating
the debug owner after the first trap, assuming the host isn't using
them.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/include/asm/kvm_host.h | 1 +
 arch/arm64/kvm/debug.c            | 9 +++++++++
 arch/arm64/kvm/sys_regs.c         | 2 ++
 3 files changed, 12 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f954b082dc4f..d76e4e44b65b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1352,6 +1352,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
 void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu);
+void kvm_handle_debug_access(struct kvm_vcpu *vcpu);
 
 #define kvm_vcpu_os_lock_enabled(vcpu)		\
 	(!!(__vcpu_sys_reg(vcpu, OSLSR_EL1) & OSLSR_EL1_OSLK))
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index e2798a4eec47..c2bf1b296b14 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -336,3 +336,12 @@ void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu)
 			vcpu->arch.debug_owner = VCPU_DEBUG_FREE;
 	}
 }
+
+void kvm_handle_debug_access(struct kvm_vcpu *vcpu)
+{
+	if (kvm_host_owns_debug_regs(vcpu))
+		return;
+
+	WARN_ON_ONCE(vcpu->arch.debug_owner == VCPU_DEBUG_GUEST_OWNED);
+	vcpu->arch.debug_owner = VCPU_DEBUG_GUEST_OWNED;
+}
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 91714639bebf..3632a4b52cc7 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -656,6 +656,7 @@ static bool trap_debug_regs(struct kvm_vcpu *vcpu,
 	if (p->is_write)
 		vcpu_set_flag(vcpu, DEBUG_DIRTY);
 
+	kvm_handle_debug_access(vcpu);
 	trace_trap_reg(__func__, r->reg, p->is_write, p->regval);
 
 	return true;
@@ -709,6 +710,7 @@ static bool trap_bvr(struct kvm_vcpu *vcpu,
 	else
 		dbg_to_reg(vcpu, p, rd, dbg_reg);
 
+	kvm_handle_debug_access(vcpu);
 	trace_trap_reg(__func__, rd->CRm, p->is_write, *dbg_reg);
 
 	return true;
-- 
2.39.5