KVM: arm64: introduce vcpu->arch.debug_ptr

This introduces a level of indirection for the debug registers. Instead
of using the sys_regs[] directly we store registers in a structure in
the vcpu. The new kvm_arm_reset_debug_ptr() sets the debug ptr to the
guest context.

Because we no longer give the sys_regs offset for the sys_reg_desc->reg
field, but instead the index into a debug-specific struct we need to
add a number of additional trap functions for each register. Also as the
generic generic user-space access code no longer works we have
introduced a new pair of function pointers to the sys_reg_desc structure
to override the generic code when needed.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/include/asm/kvm_host.h

@@ -234,5 +234,6 @@ static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 static inline void kvm_arm_init_debug(void) {}
 static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
+static inline void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) {}
 
 #endif /* __ARM_KVM_HOST_H__ */

arch/arm/kvm/arm.c

@@ -278,6 +278,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 	/* Set up the timer */
 	kvm_timer_vcpu_init(vcpu);
 
+	kvm_arm_reset_debug_ptr(vcpu);
+
 	return 0;
 }
 

arch/arm64/include/asm/kvm_asm.h

@@ -46,24 +46,16 @@
 #define	CNTKCTL_EL1	20	/* Timer Control Register (EL1) */
 #define	PAR_EL1		21	/* Physical Address Register */
 #define MDSCR_EL1	22	/* Monitor Debug System Control Register */
-#define DBGBCR0_EL1	23	/* Debug Breakpoint Control Registers (0-15) */
-#define DBGBCR15_EL1	38
-#define DBGBVR0_EL1	39	/* Debug Breakpoint Value Registers (0-15) */
-#define DBGBVR15_EL1	54
-#define DBGWCR0_EL1	55	/* Debug Watchpoint Control Registers (0-15) */
-#define DBGWCR15_EL1	70
-#define DBGWVR0_EL1	71	/* Debug Watchpoint Value Registers (0-15) */
-#define DBGWVR15_EL1	86
-#define MDCCINT_EL1	87	/* Monitor Debug Comms Channel Interrupt Enable Reg */
+#define MDCCINT_EL1	23	/* Monitor Debug Comms Channel Interrupt Enable Reg */
 
 /* 32bit specific registers. Keep them at the end of the range */
-#define	DACR32_EL2	88	/* Domain Access Control Register */
-#define	IFSR32_EL2	89	/* Instruction Fault Status Register */
-#define	FPEXC32_EL2	90	/* Floating-Point Exception Control Register */
-#define	DBGVCR32_EL2	91	/* Debug Vector Catch Register */
-#define	TEECR32_EL1	92	/* ThumbEE Configuration Register */
-#define	TEEHBR32_EL1	93	/* ThumbEE Handler Base Register */
-#define	NR_SYS_REGS	94
+#define	DACR32_EL2	24	/* Domain Access Control Register */
+#define	IFSR32_EL2	25	/* Instruction Fault Status Register */
+#define	FPEXC32_EL2	26	/* Floating-Point Exception Control Register */
+#define	DBGVCR32_EL2	27	/* Debug Vector Catch Register */
+#define	TEECR32_EL1	28	/* ThumbEE Configuration Register */
+#define	TEEHBR32_EL1	29	/* ThumbEE Handler Base Register */
+#define	NR_SYS_REGS	30
 
 /* 32bit mapping */
 #define c0_MPIDR	(MPIDR_EL1 * 2)	/* MultiProcessor ID Register */

arch/arm64/include/asm/kvm_host.h

@@ -108,11 +108,25 @@ struct kvm_vcpu_arch {
 	/* Exception Information */
 	struct kvm_vcpu_fault_info fault;
 
-	/* Debug state */
+	/* Guest debug state */
 	u64 debug_flags;
 
+	/*
+	 * We maintain more than a single set of debug registers to support
+	 * debugging the guest from the host and to maintain separate host and
+	 * guest state during world switches. vcpu_debug_state are the debug
+	 * registers of the vcpu as the guest sees them.  host_debug_state are
+	 * the host registers which are saved and restored during world switches.
+	 *
+	 * debug_ptr points to the set of debug registers that should be loaded
+	 * onto the hardware when running the guest.
+	 */
+	struct kvm_guest_debug_arch *debug_ptr;
+	struct kvm_guest_debug_arch vcpu_debug_state;
+
 	/* Pointer to host CPU context */
 	kvm_cpu_context_t *host_cpu_context;
+	struct kvm_guest_debug_arch host_debug_state;
 
 	/* VGIC state */
 	struct vgic_cpu vgic_cpu;
@@ -242,5 +256,6 @@ static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 void kvm_arm_init_debug(void);
 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);
 
 #endif /* __ARM64_KVM_HOST_H__ */

arch/arm64/kernel/asm-offsets.c

@@ -116,10 +116,16 @@ int main(void)
   DEFINE(VCPU_FAR_EL2,		offsetof(struct kvm_vcpu, arch.fault.far_el2));
   DEFINE(VCPU_HPFAR_EL2,	offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
   DEFINE(VCPU_DEBUG_FLAGS,	offsetof(struct kvm_vcpu, arch.debug_flags));
+  DEFINE(VCPU_DEBUG_PTR,	offsetof(struct kvm_vcpu, arch.debug_ptr));
+  DEFINE(DEBUG_BCR, 		offsetof(struct kvm_guest_debug_arch, dbg_bcr));
+  DEFINE(DEBUG_BVR, 		offsetof(struct kvm_guest_debug_arch, dbg_bvr));
+  DEFINE(DEBUG_WCR, 		offsetof(struct kvm_guest_debug_arch, dbg_wcr));
+  DEFINE(DEBUG_WVR, 		offsetof(struct kvm_guest_debug_arch, dbg_wvr));
   DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
   DEFINE(VCPU_MDCR_EL2,	offsetof(struct kvm_vcpu, arch.mdcr_el2));
   DEFINE(VCPU_IRQ_LINES,	offsetof(struct kvm_vcpu, arch.irq_lines));
   DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
+  DEFINE(VCPU_HOST_DEBUG_STATE, offsetof(struct kvm_vcpu, arch.host_debug_state));
   DEFINE(VCPU_TIMER_CNTV_CTL,	offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
   DEFINE(VCPU_TIMER_CNTV_CVAL,	offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_cval));
   DEFINE(KVM_TIMER_CNTVOFF,	offsetof(struct kvm, arch.timer.cntvoff));

arch/arm64/kvm/debug.c

@@ -66,6 +66,15 @@ void kvm_arm_init_debug(void)
 	__this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
 }
 
+/**
+ * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
+ */
+
+void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
+{
+	vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
+}
+
 /**
  * kvm_arm_setup_debug - set up debug related stuff
  *

arch/arm64/kvm/hyp.S

@@ -596,6 +596,7 @@ __restore_sysregs:
 /* Save debug state */
 __save_debug:
 	// x2: ptr to CPU context
+	// x3: ptr to debug reg struct
 	// x4/x5/x6-22/x24-26: trashed
 
 	mrs	x26, id_aa64dfr0_el1
@@ -606,15 +607,15 @@ __save_debug:
 	sub	w25, w26, w25		// How many WPs to skip
 
 	mov	x5, x24
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGBCR0_EL1)
+	add	x4, x3, #DEBUG_BCR
 	save_debug dbgbcr
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGBVR0_EL1)
+	add	x4, x3, #DEBUG_BVR
 	save_debug dbgbvr
 
 	mov	x5, x25
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGWCR0_EL1)
+	add	x4, x3, #DEBUG_WCR
 	save_debug dbgwcr
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGWVR0_EL1)
+	add	x4, x3, #DEBUG_WVR
 	save_debug dbgwvr
 
 	mrs	x21, mdccint_el1
@@ -624,6 +625,7 @@ __save_debug:
 /* Restore debug state */
 __restore_debug:
 	// x2: ptr to CPU context
+	// x3: ptr to debug reg struct
 	// x4/x5/x6-22/x24-26: trashed
 
 	mrs	x26, id_aa64dfr0_el1
@@ -634,15 +636,15 @@ __restore_debug:
 	sub	w25, w26, w25		// How many WPs to skip
 
 	mov	x5, x24
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGBCR0_EL1)
+	add	x4, x3, #DEBUG_BCR
 	restore_debug dbgbcr
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGBVR0_EL1)
+	add	x4, x3, #DEBUG_BVR
 	restore_debug dbgbvr
 
 	mov	x5, x25
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGWCR0_EL1)
+	add	x4, x3, #DEBUG_WCR
 	restore_debug dbgwcr
-	add	x4, x2, #CPU_SYSREG_OFFSET(DBGWVR0_EL1)
+	add	x4, x3, #DEBUG_WVR
 	restore_debug dbgwvr
 
 	ldr	x21, [x2, #CPU_SYSREG_OFFSET(MDCCINT_EL1)]
@@ -682,6 +684,7 @@ ENTRY(__kvm_vcpu_run)
 	bl __save_sysregs
 
 	compute_debug_state 1f
+	add	x3, x0, #VCPU_HOST_DEBUG_STATE
 	bl	__save_debug
 1:
 	activate_traps
@@ -697,6 +700,8 @@ ENTRY(__kvm_vcpu_run)
 	bl __restore_fpsimd
 
 	skip_debug_state x3, 1f
+	ldr	x3, [x0, #VCPU_DEBUG_PTR]
+	kern_hyp_va x3
 	bl	__restore_debug
 1:
 	restore_guest_32bit_state
@@ -717,6 +722,8 @@ __kvm_vcpu_return:
 	bl __save_sysregs
 
 	skip_debug_state x3, 1f
+	ldr	x3, [x0, #VCPU_DEBUG_PTR]
+	kern_hyp_va x3
 	bl	__save_debug
 1:
 	save_guest_32bit_state
@@ -739,6 +746,7 @@ __kvm_vcpu_return:
 	// already been saved. Note that we nuke the whole 64bit word.
 	// If we ever add more flags, we'll have to be more careful...
 	str	xzr, [x0, #VCPU_DEBUG_FLAGS]
+	add	x3, x0, #VCPU_HOST_DEBUG_STATE
 	bl	__restore_debug
 1:
 	restore_host_regs