[PATCH 4/4 v2] KVM: PPC: Add userspace debug stub support

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From: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>

This patch adds the debug stub support on booke/bookehv.
Now QEMU debug stub can use hw breakpoint, watchpoint and
software breakpoint to debug guest.

Debug registers are saved/restored on vcpu_put()/vcpu_get().
Also the debug registers are saved restored only if guest is using
debug resources.

Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
---
v2:
 - save/restore in vcpu_get()/vcpu_put()
 - some more minor cleanup based on review comments.

 arch/powerpc/include/asm/kvm_host.h |   10 ++
 arch/powerpc/include/uapi/asm/kvm.h |   22 +++-
 arch/powerpc/kvm/booke.c            |  252 ++++++++++++++++++++++++++++++++---
 arch/powerpc/kvm/e500_emulate.c     |   10 ++
 4 files changed, 272 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index f4ba881..8571952 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -504,7 +504,17 @@ struct kvm_vcpu_arch {
 	u32 mmucfg;
 	u32 epr;
 	u32 crit_save;
+	/* guest debug registers*/
 	struct kvmppc_booke_debug_reg dbg_reg;
+	/* shadow debug registers */
+	struct kvmppc_booke_debug_reg shadow_dbg_reg;
+	/* host debug registers*/
+	struct kvmppc_booke_debug_reg host_dbg_reg;
+	/*
+	 * Flag indicating that debug registers are used by guest
+	 * and requires save restore.
+	*/
+	bool debug_save_restore;
 #endif
 	gpa_t paddr_accessed;
 	gva_t vaddr_accessed;
diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
index 15f9a00..d7ce449 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -25,6 +25,7 @@
 /* Select powerpc specific features in <linux/kvm.h> */
 #define __KVM_HAVE_SPAPR_TCE
 #define __KVM_HAVE_PPC_SMT
+#define __KVM_HAVE_GUEST_DEBUG
 
 struct kvm_regs {
 	__u64 pc;
@@ -267,7 +268,24 @@ struct kvm_fpu {
 	__u64 fpr[32];
 };
 
+/*
+ * Defines for h/w breakpoint, watchpoint (read, write or both) and
+ * software breakpoint.
+ * These are used as "type" in KVM_SET_GUEST_DEBUG ioctl and "status"
+ * for KVM_DEBUG_EXIT.
+ */
+#define KVMPPC_DEBUG_NONE		0x0
+#define KVMPPC_DEBUG_BREAKPOINT		(1UL << 1)
+#define KVMPPC_DEBUG_WATCH_WRITE	(1UL << 2)
+#define KVMPPC_DEBUG_WATCH_READ		(1UL << 3)
 struct kvm_debug_exit_arch {
+	__u64 address;
+	/*
+	 * exiting to userspace because of h/w breakpoint, watchpoint
+	 * (read, write or both) and software breakpoint.
+	 */
+	__u32 status;
+	__u32 reserved;
 };
 
 /* for KVM_SET_GUEST_DEBUG */
@@ -279,10 +297,6 @@ struct kvm_guest_debug_arch {
 		 * Type denotes h/w breakpoint, read watchpoint, write
 		 * watchpoint or watchpoint (both read and write).
 		 */
-#define KVMPPC_DEBUG_NOTYPE		0x0
-#define KVMPPC_DEBUG_BREAKPOINT		(1UL << 1)
-#define KVMPPC_DEBUG_WATCH_WRITE	(1UL << 2)
-#define KVMPPC_DEBUG_WATCH_READ		(1UL << 3)
 		__u32 type;
 		__u32 reserved;
 	} bp[16];
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 1de93a8..bf20056 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -133,6 +133,30 @@ static void kvmppc_vcpu_sync_fpu(struct kvm_vcpu *vcpu)
 #endif
 }
 
+static void kvmppc_vcpu_sync_debug(struct kvm_vcpu *vcpu)
+{
+	/* Synchronize guest's desire to get debug interrupts into shadow MSR */
+#ifndef CONFIG_KVM_BOOKE_HV
+	vcpu->arch.shadow_msr &= ~MSR_DE;
+	vcpu->arch.shadow_msr |= vcpu->arch.shared->msr & MSR_DE;
+#endif
+
+	/* Force enable debug interrupts when user space wants to debug */
+	if (vcpu->guest_debug) {
+#ifdef CONFIG_KVM_BOOKE_HV
+		/*
+		 * Since there is no shadow MSR, sync MSR_DE into the guest
+		 * visible MSR. Do not allow guest to change MSR[DE].
+		 */
+		vcpu->arch.shared->msr |= MSR_DE;
+		mtspr(SPRN_MSRP, mfspr(SPRN_MSRP) | MSRP_DEP);
+#else
+		vcpu->arch.shadow_msr |= MSR_DE;
+		vcpu->arch.shared->msr &= ~MSR_DE;
+#endif
+	}
+}
+
 /*
  * Helper function for "full" MSR writes.  No need to call this if only
  * EE/CE/ME/DE/RI are changing.
@@ -150,6 +174,7 @@ void kvmppc_set_msr(struct kvm_vcpu *vcpu, u32 new_msr)
 	kvmppc_mmu_msr_notify(vcpu, old_msr);
 	kvmppc_vcpu_sync_spe(vcpu);
 	kvmppc_vcpu_sync_fpu(vcpu);
+	kvmppc_vcpu_sync_debug(vcpu);
 }
 
 static void kvmppc_booke_queue_irqprio(struct kvm_vcpu *vcpu,
@@ -736,6 +761,9 @@ static int emulation_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		run->exit_reason = KVM_EXIT_DCR;
 		return RESUME_HOST;
 
+	case EMULATE_EXIT_USER:
+		return RESUME_HOST;
+
 	case EMULATE_FAIL:
 		printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",
 		       __func__, vcpu->arch.pc, vcpu->arch.last_inst);
@@ -751,6 +779,30 @@ static int emulation_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
 	}
 }
 
+static int kvmppc_handle_debug(struct kvm_run *run, struct kvm_vcpu *vcpu)
+{
+	u32 dbsr = mfspr(SPRN_DBSR);
+	mtspr(SPRN_DBSR, dbsr);
+
+	run->debug.arch.status = 0;
+	run->debug.arch.address = vcpu->arch.pc;
+
+	if (dbsr & (DBSR_IAC1 | DBSR_IAC2 | DBSR_IAC3 | DBSR_IAC4)) {
+		run->debug.arch.status |= KVMPPC_DEBUG_BREAKPOINT;
+	} else {
+		if (dbsr & (DBSR_DAC1W | DBSR_DAC2W))
+			run->debug.arch.status |= KVMPPC_DEBUG_WATCH_WRITE;
+		else if (dbsr & (DBSR_DAC1R | DBSR_DAC2R))
+			run->debug.arch.status |= KVMPPC_DEBUG_WATCH_READ;
+		if (dbsr & (DBSR_DAC1R | DBSR_DAC1W))
+			run->debug.arch.address = vcpu->arch.shadow_dbg_reg.dac[0];
+		else if (dbsr & (DBSR_DAC2R | DBSR_DAC2W))
+			run->debug.arch.address = vcpu->arch.shadow_dbg_reg.dac[1];
+	}
+
+	return RESUME_HOST;
+}
+
 static void kvmppc_fill_pt_regs(struct pt_regs *regs)
 {
 	ulong r1, ip, msr, lr;
@@ -1110,18 +1162,10 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	}
 
 	case BOOKE_INTERRUPT_DEBUG: {
-		u32 dbsr;
-
-		vcpu->arch.pc = mfspr(SPRN_CSRR0);
-
-		/* clear IAC events in DBSR register */
-		dbsr = mfspr(SPRN_DBSR);
-		dbsr &= DBSR_IAC1 | DBSR_IAC2 | DBSR_IAC3 | DBSR_IAC4;
-		mtspr(SPRN_DBSR, dbsr);
-
-		run->exit_reason = KVM_EXIT_DEBUG;
+		r = kvmppc_handle_debug(run, vcpu);
+		if (r == RESUME_HOST)
+			run->exit_reason = KVM_EXIT_DEBUG;
 		kvmppc_account_exit(vcpu, DEBUG_EXITS);
-		r = RESUME_HOST;
 		break;
 	}
 
@@ -1172,7 +1216,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 	kvmppc_set_msr(vcpu, 0);
 
 #ifndef CONFIG_KVM_BOOKE_HV
-	vcpu->arch.shadow_msr = MSR_USER | MSR_DE | MSR_IS | MSR_DS;
+	vcpu->arch.shadow_msr = MSR_USER | MSR_IS | MSR_DS;
 	vcpu->arch.shadow_pid = 1;
 	vcpu->arch.shared->msr = 0;
 #endif
@@ -1527,12 +1571,6 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 	return r;
 }
 
-int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
-					 struct kvm_guest_debug *dbg)
-{
-	return -EINVAL;
-}
-
 int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
 {
 	return -ENOTSUPP;
@@ -1638,16 +1676,194 @@ void kvmppc_decrementer_func(unsigned long data)
 	kvmppc_set_tsr_bits(vcpu, TSR_DIS);
 }
 
+static void kvmppc_booke_vcpu_put_debug_regs(struct kvm_vcpu *vcpu)
+{
+	if (!vcpu->arch.debug_save_restore)
+		return;
+
+	/* Restore Host Context. Disable all debug events First */
+	mtspr(SPRN_DBCR0, 0x0);
+	/* Disable pending debug event by Clearing DBSR */
+	mtspr(SPRN_DBSR, mfspr(SPRN_DBSR));
+
+	mtspr(SPRN_DBCR1, vcpu->arch.host_dbg_reg.dbcr1);
+	mtspr(SPRN_DBCR2, vcpu->arch.host_dbg_reg.dbcr2);
+#ifdef CONFIG_KVM_E500MC
+	mtspr(SPRN_DBCR4, vcpu->arch.host_dbg_reg.dbcr4);
+#endif
+	mtspr(SPRN_IAC1, vcpu->arch.host_dbg_reg.iac[0]);
+	mtspr(SPRN_IAC2, vcpu->arch.host_dbg_reg.iac[1]);
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
+	mtspr(SPRN_IAC3, vcpu->arch.host_dbg_reg.iac[2]);
+	mtspr(SPRN_IAC4, vcpu->arch.host_dbg_reg.iac[3]);
+#endif
+	mtspr(SPRN_DAC1, vcpu->arch.host_dbg_reg.dac[0]);
+	mtspr(SPRN_DAC2, vcpu->arch.host_dbg_reg.dac[1]);
+
+	/* Enable debug events after all other debug registers restored */
+	mtspr(SPRN_DBCR0, vcpu->arch.host_dbg_reg.dbcr0);
+
+	/* Host debug register are restored */
+	vcpu->arch.debug_save_restore = false;
+}
+
+static void kvmppc_booke_vcpu_load_debug_regs(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * Check whether guest still need debug resource, if not then there
+	 * is no need to resotre guest context.
+	 */
+	if (!vcpu->arch.shadow_dbg_reg.dbcr0)
+		return;
+
+	/*
+	 * Save Host debug register only after restore. If host debug
+	 * registers are saved and not restored then do not save again.
+	 */
+	if (!vcpu->arch.debug_save_restore) {
+		/* Save Host context */
+		vcpu->arch.host_dbg_reg.dbcr0 = mfspr(SPRN_DBCR0);
+		vcpu->arch.host_dbg_reg.dbcr1 = mfspr(SPRN_DBCR1);
+		vcpu->arch.host_dbg_reg.dbcr2 = mfspr(SPRN_DBCR2);
+#ifdef CONFIG_KVM_E500MC
+		vcpu->arch.host_dbg_reg.dbcr4 = mfspr(SPRN_DBCR4);
+#endif
+		vcpu->arch.host_dbg_reg.iac[0] = mfspr(SPRN_IAC1);
+		vcpu->arch.host_dbg_reg.iac[1] = mfspr(SPRN_IAC2);
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
+		vcpu->arch.host_dbg_reg.iac[2] = mfspr(SPRN_IAC3);
+		vcpu->arch.host_dbg_reg.iac[3] = mfspr(SPRN_IAC4);
+#endif
+		vcpu->arch.host_dbg_reg.dac[0] = mfspr(SPRN_DAC1);
+		vcpu->arch.host_dbg_reg.dac[1] = mfspr(SPRN_DAC2);
+		vcpu->arch.debug_save_restore = true;
+	}
+
+	/* Restore Guest Context. Disable all debug events First */
+	mtspr(SPRN_DBCR0, 0x0);
+	/* Clear h/w DBSR */
+	mtspr(SPRN_DBSR, mfspr(SPRN_DBSR));
+
+	mtspr(SPRN_DBCR1, vcpu->arch.shadow_dbg_reg.dbcr1);
+	mtspr(SPRN_DBCR2, vcpu->arch.shadow_dbg_reg.dbcr2);
+#ifdef CONFIG_KVM_E500MC
+	mtspr(SPRN_DBCR4, vcpu->arch.shadow_dbg_reg.dbcr4);
+#endif
+	mtspr(SPRN_IAC1, vcpu->arch.shadow_dbg_reg.iac[0]);
+	mtspr(SPRN_IAC2, vcpu->arch.shadow_dbg_reg.iac[1]);
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
+	mtspr(SPRN_IAC3, vcpu->arch.shadow_dbg_reg.iac[2]);
+	mtspr(SPRN_IAC4, vcpu->arch.shadow_dbg_reg.iac[3]);
+#endif
+	mtspr(SPRN_DAC1, vcpu->arch.shadow_dbg_reg.dac[0]);
+	mtspr(SPRN_DAC2, vcpu->arch.shadow_dbg_reg.dac[1]);
+
+	/* Enable debug events after other debug registers restored */
+	mtspr(SPRN_DBCR0, vcpu->arch.shadow_dbg_reg.dbcr0);
+}
+
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					 struct kvm_guest_debug *dbg)
+{
+	struct kvmppc_booke_debug_reg *dbg_reg;
+	int n, b = 0, w = 0;
+	const u32 bp_code[] = {
+		DBCR0_IAC1 | DBCR0_IDM,
+		DBCR0_IAC2 | DBCR0_IDM,
+		DBCR0_IAC3 | DBCR0_IDM,
+		DBCR0_IAC4 | DBCR0_IDM
+	};
+	const u32 wp_code[] = {
+		DBCR0_DAC1W | DBCR0_IDM,
+		DBCR0_DAC2W | DBCR0_IDM,
+		DBCR0_DAC1R | DBCR0_IDM,
+		DBCR0_DAC2R | DBCR0_IDM
+	};
+
+	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
+		/* Clear All debug events */
+		vcpu->arch.shadow_dbg_reg.dbcr0 = 0;
+		vcpu->guest_debug = 0;
+		return 0;
+	}
+
+	vcpu->guest_debug = dbg->control;
+	vcpu->arch.shadow_dbg_reg.dbcr0 = 0;
+	/* Set DBCR0_EDM in guest visible DBCR0 register. */
+	vcpu->arch.dbg_reg.dbcr0 = DBCR0_EDM;
+
+	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
+		vcpu->arch.shadow_dbg_reg.dbcr0 |= DBCR0_IDM | DBCR0_IC;
+
+	if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)) {
+		/* Code below handles only HW breakpoints */
+		kvmppc_booke_vcpu_load_debug_regs(vcpu);
+		return 0;
+	}
+
+	dbg_reg = &(vcpu->arch.shadow_dbg_reg);
+
+	/*
+	 * On BOOKE (e500v2); Set DBCR1 and DBCR2 to allow debug events
+	 * to occur when MSR.PR is set.
+	 * On BOOKE-HV (e500mc+); MSR.PR = 0 when guest is running. So we
+	 * should clear DBCR1 and DBCR2.
+	 */
+#ifdef CONFIG_KVM_BOOKE_HV
+	dbg_reg->dbcr1 = 0;
+	dbg_reg->dbcr2 = 0;
+#else
+	dbg_reg->dbcr1 = DBCR1_IAC1US | DBCR1_IAC2US | DBCR1_IAC3US |
+			  DBCR1_IAC4US;
+	dbg_reg->dbcr2 = DBCR2_DAC1US | DBCR2_DAC2US;
+#endif
+
+	for (n = 0; n < (KVMPPC_BOOKE_IAC_NUM + KVMPPC_BOOKE_DAC_NUM); n++) {
+		u32 type = dbg->arch.bp[n].type;
+
+		if (!type)
+			break;
+
+		if (type & (KVMPPC_DEBUG_WATCH_READ |
+			    KVMPPC_DEBUG_WATCH_WRITE)) {
+			if (w >= KVMPPC_BOOKE_DAC_NUM)
+				continue;
+
+			if (type & KVMPPC_DEBUG_WATCH_READ)
+				dbg_reg->dbcr0 |= wp_code[w + 2];
+			if (type & KVMPPC_DEBUG_WATCH_WRITE)
+				dbg_reg->dbcr0 |= wp_code[w];
+
+			dbg_reg->dac[w] = dbg->arch.bp[n].addr;
+			w++;
+		} else if (type & KVMPPC_DEBUG_BREAKPOINT) {
+			if (b >= KVMPPC_BOOKE_IAC_NUM)
+				continue;
+
+			dbg_reg->dbcr0 |= bp_code[b];
+			dbg_reg->iac[b] = dbg->arch.bp[n].addr;
+			b++;
+		}
+	}
+
+	kvmppc_booke_vcpu_load_debug_regs(vcpu);
+	return 0;
+}
+
 void kvmppc_booke_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 	vcpu->cpu = smp_processor_id();
 	current->thread.kvm_vcpu = vcpu;
+
+	kvmppc_booke_vcpu_load_debug_regs(vcpu);
 }
 
 void kvmppc_booke_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	current->thread.kvm_vcpu = NULL;
 	vcpu->cpu = -1;
+
+	kvmppc_booke_vcpu_put_debug_regs(vcpu);
 }
 
 int __init kvmppc_booke_init(void)
diff --git a/arch/powerpc/kvm/e500_emulate.c b/arch/powerpc/kvm/e500_emulate.c
index e78f353..cefdd38 100644
--- a/arch/powerpc/kvm/e500_emulate.c
+++ b/arch/powerpc/kvm/e500_emulate.c
@@ -26,6 +26,7 @@
 #define XOP_TLBRE   946
 #define XOP_TLBWE   978
 #define XOP_TLBILX  18
+#define XOP_EHPRIV  270
 
 #ifdef CONFIG_KVM_E500MC
 static int dbell2prio(ulong param)
@@ -130,6 +131,15 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			emulated = kvmppc_e500_emul_tlbivax(vcpu, ea);
 			break;
 
+		case XOP_EHPRIV:
+			run->exit_reason = KVM_EXIT_DEBUG;
+			run->debug.arch.address = vcpu->arch.pc;
+			run->debug.arch.status = 0;
+			kvmppc_account_exit(vcpu, DEBUG_EXITS);
+			emulated = EMULATE_EXIT_USER;
+			*advance = 0;
+			break;
+
 		default:
 			emulated = EMULATE_FAIL;
 		}
-- 
1.7.0.4


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