1 files changed, 68 insertions, 19 deletions

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index db9361338b2a..fccf9ec01813 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -32,6 +32,10 @@ static DEFINE_PER_CPU(u64, mdcr_el2);
  *
  * Guest access to MDSCR_EL1 is trapped by the hypervisor and handled
  * after we have restored the preserved value to the main context.
+ *
+ * When single-step is enabled by userspace, we tweak PSTATE.SS on every
+ * guest entry. Preserve PSTATE.SS so we can restore the original value
+ * for the vcpu after the single-step is disabled.
  */
 static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
 {
@@ -41,6 +45,9 @@ static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
 
 	trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
 				vcpu->arch.guest_debug_preserved.mdscr_el1);
+
+	vcpu->arch.guest_debug_preserved.pstate_ss =
+					(*vcpu_cpsr(vcpu) & DBG_SPSR_SS);
 }
 
 static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
@@ -51,6 +58,11 @@ static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
 
 	trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
 				vcpu_read_sys_reg(vcpu, MDSCR_EL1));
+
+	if (vcpu->arch.guest_debug_preserved.pstate_ss)
+		*vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+	else
+		*vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
 }
 
 /**
@@ -104,10 +116,12 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
 	 * Trap debug register access when one of the following is true:
 	 *  - Userspace is using the hardware to debug the guest
 	 *  (KVM_GUESTDBG_USE_HW is set).
-	 *  - The guest is not using debug (KVM_ARM64_DEBUG_DIRTY is clear).
+	 *  - The guest is not using debug (DEBUG_DIRTY clear).
+	 *  - The guest has enabled the OS Lock (debug exceptions are blocked).
 	 */
 	if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) ||
-	    !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
+	    !vcpu_get_flag(vcpu, DEBUG_DIRTY) ||
+	    kvm_vcpu_os_lock_enabled(vcpu))
 		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
 
 	trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
@@ -145,8 +159,8 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
  * debug related registers.
  *
  * Additionally, KVM only traps guest accesses to the debug registers if
- * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
- * flag on vcpu->arch.flags).  Since the guest must not interfere
+ * the guest is not actively using them (see the DEBUG_DIRTY
+ * flag on vcpu->arch.iflags).  Since the guest must not interfere
  * with the hardware state when debugging the guest, we must ensure that
  * trapping is enabled whenever we are debugging the guest using the
  * debug registers.
@@ -160,8 +174,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 
 	kvm_arm_setup_mdcr_el2(vcpu);
 
-	/* Is Guest debugging in effect? */
-	if (vcpu->guest_debug) {
+	/* Check if we need to use the debug registers. */
+	if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
 		/* Save guest debug state */
 		save_guest_debug_regs(vcpu);
 
@@ -186,7 +200,18 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 		 * debugging the system.
 		 */
 		if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
-			*vcpu_cpsr(vcpu) |=  DBG_SPSR_SS;
+			/*
+			 * If the software step state at the last guest exit
+			 * was Active-pending, we don't set DBG_SPSR_SS so
+			 * that the state is maintained (to not run another
+			 * single-step until the pending Software Step
+			 * exception is taken).
+			 */
+			if (!vcpu_get_flag(vcpu, DBG_SS_ACTIVE_PENDING))
+				*vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+			else
+				*vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
+
 			mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
 			mdscr |= DBG_MDSCR_SS;
 			vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
@@ -203,9 +228,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 		 *
 		 * We simply switch the debug_ptr to point to our new
 		 * external_debug_state which has been populated by the
-		 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
-		 * mechanism ensures the registers are updated on the
-		 * world switch.
+		 * debug ioctl. The existing DEBUG_DIRTY mechanism ensures
+		 * the registers are updated on the world switch.
 		 */
 		if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
 			/* Enable breakpoints/watchpoints */
@@ -214,7 +238,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 			vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
 
 			vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
-			vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
+			vcpu_set_flag(vcpu, DEBUG_DIRTY);
 
 			trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
 						&vcpu->arch.debug_ptr->dbg_bcr[0],
@@ -223,6 +247,19 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 			trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
 						&vcpu->arch.debug_ptr->dbg_wcr[0],
 						&vcpu->arch.debug_ptr->dbg_wvr[0]);
+
+		/*
+		 * The OS Lock blocks debug exceptions in all ELs when it is
+		 * enabled. If the guest has enabled the OS Lock, constrain its
+		 * effects to the guest. Emulate the behavior by clearing
+		 * MDSCR_EL1.MDE. In so doing, we ensure that host debug
+		 * exceptions are unaffected by guest configuration of the OS
+		 * Lock.
+		 */
+		} else if (kvm_vcpu_os_lock_enabled(vcpu)) {
+			mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+			mdscr &= ~DBG_MDSCR_MDE;
+			vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
 		}
 	}
 
@@ -231,7 +268,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 
 	/* If KDE or MDE are set, perform a full save/restore cycle. */
 	if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
-		vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
+		vcpu_set_flag(vcpu, DEBUG_DIRTY);
 
 	/* Write mdcr_el2 changes since vcpu_load on VHE systems */
 	if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2)
@@ -244,7 +281,19 @@ void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
 {
 	trace_kvm_arm_clear_debug(vcpu->guest_debug);
 
-	if (vcpu->guest_debug) {
+	/*
+	 * Restore the guest's debug registers if we were using them.
+	 */
+	if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
+		if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+			if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS))
+				/*
+				 * Mark the vcpu as ACTIVE_PENDING
+				 * until Software Step exception is taken.
+				 */
+				vcpu_set_flag(vcpu, DBG_SS_ACTIVE_PENDING);
+		}
+
 		restore_guest_debug_regs(vcpu);
 
 		/*
@@ -278,18 +327,18 @@ void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu)
 	 * If SPE is present on this CPU and is available at current EL,
 	 * we may need to check if the host state needs to be saved.
 	 */
-	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_PMSVER_SHIFT) &&
+	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&
 	    !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(SYS_PMBIDR_EL1_P_SHIFT)))
-		vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_SPE;
+		vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_SPE);
 
 	/* Check if we have TRBE implemented and available at the host */
-	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_TRBE_SHIFT) &&
+	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
 	    !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG))
-		vcpu->arch.flags |= KVM_ARM64_DEBUG_STATE_SAVE_TRBE;
+		vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
 }
 
 void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu)
 {
-	vcpu->arch.flags &= ~(KVM_ARM64_DEBUG_STATE_SAVE_SPE |
-			      KVM_ARM64_DEBUG_STATE_SAVE_TRBE);
+	vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE);
+	vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
 }