[PATCH 0/4 v6] KVM :PPC: Userspace Debug support

[PATCH 0/4 v6] KVM :PPC: Userspace Debug support

[Bharat Bhushan]

From: Bharat Bhushan <bharat.bhushan@freescale.com>

Note: These patches depends on https://lkml.org/lkml/2013/7/4/49.

This patchset adds the userspace debug support for booke/bookehv.
this is tested on powerpc e500v2/e500mc devices.

We are now assuming that debug resource will not be used by kernel for
its own debugging. It will be used for only kernel user process debugging.
So the kernel debug load interface during context_to is used to load
debug conext for that selected process.

v5->v6
 - Earlier it was a patchset of six patches. Now this is devided into
   two parts: 1) powerpc spcific changes 2) kvm specific changes.
   This patchset now contains only KVM specific changes.
 - using "ehpriv 1" (earlier using "ehpriv") for software breakpoint
 -

v4->v5
 - Some comments reworded and other cleanup (like change of function name etc)
 - Added a function for setting MSRP rather than inline

v3->v4
 - 4 out of 7 patches of initial patchset were applied.
   This patchset is on and above those 4 patches
 - KVM local "struct kvmppc_booke_debug_reg" is replaced by
   powerpc global "struct debug_reg"
 - use switch_booke_debug_regs() for debug register context switch.
 - Save DBSR before kernel pre-emption is enabled.
 - Some more cleanup

v2->v3
 - We are now assuming that debug resource will not be used by
   kernel for its own debugging.
   It will be used for only kernel user process debugging.
   So the kernel debug load interface during context_to is
   used to load debug conext for that selected process.

v1->v2
 - Debug registers are save/restore in vcpu_put/vcpu_get.
   Earlier the debug registers are saved/restored in guest entry/exit

Bharat Bhushan (4):
  powerpc: export debug registers save function for KVM
  KVM: PPC: exit to user space on "ehpriv 1" instruction
  KVM: PPC: Using "struct debug_reg"
  KVM: PPC: Add userspace debug stub support

 arch/powerpc/include/asm/disassemble.h |    4 +
 arch/powerpc/include/asm/kvm_booke.h   |    7 +-
 arch/powerpc/include/asm/kvm_host.h    |   16 +--
 arch/powerpc/include/asm/switch_to.h   |    1 +
 arch/powerpc/include/uapi/asm/kvm.h    |   22 ++-
 arch/powerpc/kernel/process.c          |    3 +-
 arch/powerpc/kvm/booke.c               |  275 ++++++++++++++++++++++++++++----
 arch/powerpc/kvm/booke.h               |    5 +
 arch/powerpc/kvm/e500_emulate.c        |   26 +++
 9 files changed, 312 insertions(+), 47 deletions(-)

[PATCH 1/4 v6] powerpc: export debug registers save function for KVM

[Bharat Bhushan]

KVM need this function when switching from vcpu to user-space
thread. My subsequent patch will use this function.

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v5->v6
 - switch_booke_debug_regs() not guarded by the compiler switch

 arch/powerpc/include/asm/switch_to.h |    1 +
 arch/powerpc/kernel/process.c        |    3 ++-
 2 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 200d763..db68f1d 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -29,6 +29,7 @@ extern void giveup_vsx(struct task_struct *);
 extern void enable_kernel_spe(void);
 extern void giveup_spe(struct task_struct *);
 extern void load_up_spe(struct task_struct *);
+extern void switch_booke_debug_regs(struct thread_struct *new_thread);
 
 #ifndef CONFIG_SMP
 extern void discard_lazy_cpu_state(void);
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 01ff496..da586aa 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -362,12 +362,13 @@ static void prime_debug_regs(struct thread_struct *thread)
  * debug registers, set the debug registers from the values
  * stored in the new thread.
  */
-static void switch_booke_debug_regs(struct thread_struct *new_thread)
+void switch_booke_debug_regs(struct thread_struct *new_thread)
 {
 	if ((current->thread.debug.dbcr0 & DBCR0_IDM)
 		|| (new_thread->debug.dbcr0 & DBCR0_IDM))
 			prime_debug_regs(new_thread);
 }
+EXPORT_SYMBOL_GPL(switch_booke_debug_regs);
 #else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
 #ifndef CONFIG_HAVE_HW_BREAKPOINT
 static void set_debug_reg_defaults(struct thread_struct *thread)
-- 
1.7.0.4

Re: [PATCH 1/4 v6] powerpc: export debug registers save function for KVM

[Alexander Graf]

On 04.07.2013, at 08:57, Bharat Bhushan wrote:

> KVM need this function when switching from vcpu to user-space
> thread. My subsequent patch will use this function.
>=20
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>

Ben / Michael, please ack.


Alex

> ---
> v5->v6
> - switch_booke_debug_regs() not guarded by the compiler switch
>=20
> arch/powerpc/include/asm/switch_to.h |    1 +
> arch/powerpc/kernel/process.c        |    3 ++-
> 2 files changed, 3 insertions(+), 1 deletions(-)
>=20
> diff --git a/arch/powerpc/include/asm/switch_to.h =
b/arch/powerpc/include/asm/switch_to.h
> index 200d763..db68f1d 100644
> --- a/arch/powerpc/include/asm/switch_to.h
> +++ b/arch/powerpc/include/asm/switch_to.h
> @@ -29,6 +29,7 @@ extern void giveup_vsx(struct task_struct *);
> extern void enable_kernel_spe(void);
> extern void giveup_spe(struct task_struct *);
> extern void load_up_spe(struct task_struct *);
> +extern void switch_booke_debug_regs(struct thread_struct =
*new_thread);
>=20
> #ifndef CONFIG_SMP
> extern void discard_lazy_cpu_state(void);
> diff --git a/arch/powerpc/kernel/process.c =
b/arch/powerpc/kernel/process.c
> index 01ff496..da586aa 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -362,12 +362,13 @@ static void prime_debug_regs(struct =
thread_struct *thread)
>  * debug registers, set the debug registers from the values
>  * stored in the new thread.
>  */
> -static void switch_booke_debug_regs(struct thread_struct *new_thread)
> +void switch_booke_debug_regs(struct thread_struct *new_thread)
> {
> 	if ((current->thread.debug.dbcr0 & DBCR0_IDM)
> 		|| (new_thread->debug.dbcr0 & DBCR0_IDM))
> 			prime_debug_regs(new_thread);
> }
> +EXPORT_SYMBOL_GPL(switch_booke_debug_regs);
> #else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
> #ifndef CONFIG_HAVE_HW_BREAKPOINT
> static void set_debug_reg_defaults(struct thread_struct *thread)
> --=20
> 1.7.0.4
>=20
>=20
> --
> To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 1/4 v6] powerpc: export debug registers save function for KVM

[Michael Neuling]

Alexander Graf <agraf@suse.de> wrote:

> 
> On 04.07.2013, at 08:57, Bharat Bhushan wrote:
> 
> > KVM need this function when switching from vcpu to user-space
> > thread. My subsequent patch will use this function.
> > 
> > Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> 
> Ben / Michael, please ack.

It's not really my area of expertise, but it applies and compiles for me
and it's relatively simple, so FWIW...

Acked-by: Michael Neuling <mikey@neuling.org>

> 
> 
> Alex
> 
> > ---
> > v5->v6
> > - switch_booke_debug_regs() not guarded by the compiler switch
> > 
> > arch/powerpc/include/asm/switch_to.h |    1 +
> > arch/powerpc/kernel/process.c        |    3 ++-
> > 2 files changed, 3 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
> > index 200d763..db68f1d 100644
> > --- a/arch/powerpc/include/asm/switch_to.h
> > +++ b/arch/powerpc/include/asm/switch_to.h
> > @@ -29,6 +29,7 @@ extern void giveup_vsx(struct task_struct *);
> > extern void enable_kernel_spe(void);
> > extern void giveup_spe(struct task_struct *);
> > extern void load_up_spe(struct task_struct *);
> > +extern void switch_booke_debug_regs(struct thread_struct *new_thread);
> > 
> > #ifndef CONFIG_SMP
> > extern void discard_lazy_cpu_state(void);
> > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> > index 01ff496..da586aa 100644
> > --- a/arch/powerpc/kernel/process.c
> > +++ b/arch/powerpc/kernel/process.c
> > @@ -362,12 +362,13 @@ static void prime_debug_regs(struct thread_struct *thread)
> >  * debug registers, set the debug registers from the values
> >  * stored in the new thread.
> >  */
> > -static void switch_booke_debug_regs(struct thread_struct *new_thread)
> > +void switch_booke_debug_regs(struct thread_struct *new_thread)
> > {
> > 	if ((current->thread.debug.dbcr0 & DBCR0_IDM)
> > 		|| (new_thread->debug.dbcr0 & DBCR0_IDM))
> > 			prime_debug_regs(new_thread);
> > }
> > +EXPORT_SYMBOL_GPL(switch_booke_debug_regs);
> > #else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
> > #ifndef CONFIG_HAVE_HW_BREAKPOINT
> > static void set_debug_reg_defaults(struct thread_struct *thread)
> > -- 
> > 1.7.0.4
> > 
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

[PATCH 2/4 v6] KVM: PPC: exit to user space on "ehpriv 1" instruction

[Bharat Bhushan]

"ehpriv 1" instruction is used for setting software breakpoints
by user space. This patch adds support to exit to user space
with "run->debug" have relevant information.

As this is the first point we are using run->debug, also defined
the run->debug structure.

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v5->v6
 - using "ehpriv 1" instread of "ehpriv" for software breakpoint

 arch/powerpc/include/asm/disassemble.h |    4 ++++
 arch/powerpc/include/asm/kvm_booke.h   |    7 ++++++-
 arch/powerpc/include/uapi/asm/kvm.h    |   21 +++++++++++++++++----
 arch/powerpc/kvm/booke.c               |    2 +-
 arch/powerpc/kvm/e500_emulate.c        |   26 ++++++++++++++++++++++++++
 5 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/disassemble.h b/arch/powerpc/include/asm/disassemble.h
index 9b198d1..856f8de 100644
--- a/arch/powerpc/include/asm/disassemble.h
+++ b/arch/powerpc/include/asm/disassemble.h
@@ -77,4 +77,8 @@ static inline unsigned int get_d(u32 inst)
 	return inst & 0xffff;
 }
 
+static inline unsigned int get_oc(u32 inst)
+{
+	return (inst >> 11) & 0x7fff;
+}
 #endif /* __ASM_PPC_DISASSEMBLE_H__ */
diff --git a/arch/powerpc/include/asm/kvm_booke.h b/arch/powerpc/include/asm/kvm_booke.h
index d3c1eb3..dd8f615 100644
--- a/arch/powerpc/include/asm/kvm_booke.h
+++ b/arch/powerpc/include/asm/kvm_booke.h
@@ -26,7 +26,12 @@
 /* LPIDs we support with this build -- runtime limit may be lower */
 #define KVMPPC_NR_LPIDS                        64
 
-#define KVMPPC_INST_EHPRIV	0x7c00021c
+#define KVMPPC_INST_EHPRIV		0x7c00021c
+#define EHPRIV_OC_SHIFT			11
+/* "ehpriv 1" : ehpriv with OC = 1 is used for debug emulation */
+#define EHPRIV_OC_DEBUG			1
+#define KVMPPC_INST_EHPRIV_DEBUG	(KVMPPC_INST_EHPRIV | \
+					 (EHPRIV_OC_DEBUG << EHPRIV_OC_SHIFT))
 
 static inline void kvmppc_set_gpr(struct kvm_vcpu *vcpu, int num, ulong val)
 {
diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
index 0fb1a6e..ded0607 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -269,7 +269,24 @@ 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 */
@@ -281,10 +298,6 @@ struct kvm_guest_debug_arch {
 		 * Type denotes h/w breakpoint, read watchpoint, write
 		 * watchpoint or watchpoint (both read and write).
 		 */
-#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)
 		__u32 type;
 		__u32 reserved;
 	} bp[16];
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 62d4ece..4c9f6ad 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -1460,7 +1460,7 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 		val = get_reg_val(reg->id, vcpu->arch.tsr);
 		break;
 	case KVM_REG_PPC_DEBUG_INST:
-		val = get_reg_val(reg->id, KVMPPC_INST_EHPRIV);
+		val = get_reg_val(reg->id, KVMPPC_INST_EHPRIV_DEBUG);
 		break;
 	default:
 		r = kvmppc_get_one_reg(vcpu, reg->id, &val);
diff --git a/arch/powerpc/kvm/e500_emulate.c b/arch/powerpc/kvm/e500_emulate.c
index b10a012..6163a03 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)
@@ -82,6 +83,26 @@ static int kvmppc_e500_emul_msgsnd(struct kvm_vcpu *vcpu, int rb)
 }
 #endif
 
+static int kvmppc_e500_emul_ehpriv(struct kvm_run *run, struct kvm_vcpu *vcpu,
+				   unsigned int inst, int *advance)
+{
+	int emulated = EMULATE_DONE;
+
+	switch (get_oc(inst)) {
+	case EHPRIV_OC_DEBUG:
+		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;
+	}
+	return emulated;
+}
+
 int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
                            unsigned int inst, int *advance)
 {
@@ -130,6 +151,11 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			emulated = kvmppc_e500_emul_tlbivax(vcpu, ea);
 			break;
 
+		case XOP_EHPRIV:
+			emulated = kvmppc_e500_emul_ehpriv(run, vcpu, inst,
+							   advance);
+			break;
+
 		default:
 			emulated = EMULATE_FAIL;
 		}
-- 
1.7.0.4

[PATCH 3/4 v6] KVM: PPC: Using "struct debug_reg"

[Bharat Bhushan]

For KVM also use the "struct debug_reg" defined in asm/processor.h

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v5->v6
 - no changes

 arch/powerpc/include/asm/kvm_host.h |   13 +------------
 arch/powerpc/kvm/booke.c            |   34 ++++++++++++++++++++++++----------
 2 files changed, 25 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index af326cd..838a577 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -381,17 +381,6 @@ struct kvmppc_slb {
 #define KVMPPC_EPR_USER		1 /* exit to userspace to fill EPR */
 #define KVMPPC_EPR_KERNEL	2 /* in-kernel irqchip */
 
-struct kvmppc_booke_debug_reg {
-	u32 dbcr0;
-	u32 dbcr1;
-	u32 dbcr2;
-#ifdef CONFIG_KVM_E500MC
-	u32 dbcr4;
-#endif
-	u64 iac[KVMPPC_BOOKE_MAX_IAC];
-	u64 dac[KVMPPC_BOOKE_MAX_DAC];
-};
-
 #define KVMPPC_IRQ_DEFAULT	0
 #define KVMPPC_IRQ_MPIC		1
 #define KVMPPC_IRQ_XICS		2
@@ -535,7 +524,7 @@ struct kvm_vcpu_arch {
 	u32 eptcfg;
 	u32 epr;
 	u32 crit_save;
-	struct kvmppc_booke_debug_reg dbg_reg;
+	struct debug_reg dbg_reg;
 #endif
 	gpa_t paddr_accessed;
 	gva_t vaddr_accessed;
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 4c9f6ad..87aa727 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -1424,7 +1424,6 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 	int r = 0;
 	union kvmppc_one_reg val;
 	int size;
-	long int i;
 
 	size = one_reg_size(reg->id);
 	if (size > sizeof(val))
@@ -1432,16 +1431,24 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 
 	switch (reg->id) {
 	case KVM_REG_PPC_IAC1:
+		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.iac1);
+		break;
 	case KVM_REG_PPC_IAC2:
+		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.iac2);
+		break;
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
 	case KVM_REG_PPC_IAC3:
+		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.iac3);
+		break;
 	case KVM_REG_PPC_IAC4:
-		i = reg->id - KVM_REG_PPC_IAC1;
-		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.iac[i]);
+		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.iac4);
 		break;
+#endif
 	case KVM_REG_PPC_DAC1:
+		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.dac1);
+		break;
 	case KVM_REG_PPC_DAC2:
-		i = reg->id - KVM_REG_PPC_DAC1;
-		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.dac[i]);
+		val = get_reg_val(reg->id, vcpu->arch.dbg_reg.dac2);
 		break;
 	case KVM_REG_PPC_EPR: {
 		u32 epr = get_guest_epr(vcpu);
@@ -1481,7 +1488,6 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 	int r = 0;
 	union kvmppc_one_reg val;
 	int size;
-	long int i;
 
 	size = one_reg_size(reg->id);
 	if (size > sizeof(val))
@@ -1492,16 +1498,24 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 
 	switch (reg->id) {
 	case KVM_REG_PPC_IAC1:
+		vcpu->arch.dbg_reg.iac1 = set_reg_val(reg->id, val);
+		break;
 	case KVM_REG_PPC_IAC2:
+		vcpu->arch.dbg_reg.iac2 = set_reg_val(reg->id, val);
+		break;
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
 	case KVM_REG_PPC_IAC3:
+		vcpu->arch.dbg_reg.iac3 = set_reg_val(reg->id, val);
+		break;
 	case KVM_REG_PPC_IAC4:
-		i = reg->id - KVM_REG_PPC_IAC1;
-		vcpu->arch.dbg_reg.iac[i] = set_reg_val(reg->id, val);
+		vcpu->arch.dbg_reg.iac4 = set_reg_val(reg->id, val);
 		break;
+#endif
 	case KVM_REG_PPC_DAC1:
+		vcpu->arch.dbg_reg.dac1 = set_reg_val(reg->id, val);
+		break;
 	case KVM_REG_PPC_DAC2:
-		i = reg->id - KVM_REG_PPC_DAC1;
-		vcpu->arch.dbg_reg.dac[i] = set_reg_val(reg->id, val);
+		vcpu->arch.dbg_reg.dac2 = set_reg_val(reg->id, val);
 		break;
 	case KVM_REG_PPC_EPR: {
 		u32 new_epr = set_reg_val(reg->id, val);
-- 
1.7.0.4

[PATCH 4/4 v6] KVM: PPC: Add userspace debug stub support

[Bharat Bhushan]

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.

This is how we save/restore debug register context when switching
between guest, userspace and kernel user-process:

When QEMU is running
 -> thread->debug_reg == QEMU debug register context.
 -> Kernel will handle switching the debug register on context switch.
 -> no vcpu_load() called

QEMU makes ioctls (except RUN)
 -> This will call vcpu_load()
 -> should not change context.
 -> Some ioctls can change vcpu debug register, context saved in vcpu->debug_regs

QEMU Makes RUN ioctl
 -> Save thread->debug_reg on STACK
 -> Store thread->debug_reg == vcpu->debug_reg
 -> load thread->debug_reg
 -> RUN VCPU ( So thread points to vcpu context )

Context switch happens When VCPU running
 -> makes vcpu_load() should not load any context
 -> kernel loads the vcpu context as thread->debug_regs points to vcpu context.

On heavyweight_exit
 -> Load the context saved on stack in thread->debug_reg

Currently we do not support debug resource emulation to guest,
On debug exception, always exit to user space irrespective of
user space is expecting the debug exception or not. If this is
unexpected exception (breakpoint/watchpoint event not set by
userspace) then let us leave the action on user space. This
is similar to what it was before, only thing is that now we
have proper exit state available to user space.

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v5->v6
 - no changes

 arch/powerpc/include/asm/kvm_host.h |    3 +
 arch/powerpc/include/uapi/asm/kvm.h |    1 +
 arch/powerpc/kvm/booke.c            |  239 ++++++++++++++++++++++++++++++++---
 arch/powerpc/kvm/booke.h            |    5 +
 4 files changed, 230 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 838a577..aeb490d 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -524,7 +524,10 @@ struct kvm_vcpu_arch {
 	u32 eptcfg;
 	u32 epr;
 	u32 crit_save;
+	/* guest debug registers*/
 	struct debug_reg dbg_reg;
+	/* hardware visible debug registers when in guest state */
+	struct debug_reg shadow_dbg_reg;
 #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 ded0607..f5077c2 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -27,6 +27,7 @@
 #define __KVM_HAVE_PPC_SMT
 #define __KVM_HAVE_IRQCHIP
 #define __KVM_HAVE_IRQ_LINE
+#define __KVM_HAVE_GUEST_DEBUG
 
 struct kvm_regs {
 	__u64 pc;
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 87aa727..7b54802 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -133,6 +133,29 @@ 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.
+		 */
+		vcpu->arch.shared->msr |= MSR_DE;
+#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 +173,7 @@ 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,
@@ -655,6 +679,7 @@ int kvmppc_core_check_requests(struct kvm_vcpu *vcpu)
 int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 {
 	int ret, s;
+	struct thread_struct thread;
 #ifdef CONFIG_PPC_FPU
 	unsigned int fpscr;
 	int fpexc_mode;
@@ -698,12 +723,21 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 
 	kvmppc_load_guest_fp(vcpu);
 #endif
+	/* Switch to guest debug context */
+	thread.debug = vcpu->arch.shadow_dbg_reg;
+	switch_booke_debug_regs(&thread);
+	thread.debug = current->thread.debug;
+	current->thread.debug = vcpu->arch.shadow_dbg_reg;
 
 	ret = __kvmppc_vcpu_run(kvm_run, vcpu);
 
 	/* No need for kvm_guest_exit. It's done in handle_exit.
 	   We also get here with interrupts enabled. */
 
+	/* Switch back to user space debug context */
+	switch_booke_debug_regs(&thread);
+	current->thread.debug = thread.debug;
+
 #ifdef CONFIG_PPC_FPU
 	kvmppc_save_guest_fp(vcpu);
 
@@ -759,6 +793,30 @@ 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)
+{
+	struct debug_reg *dbg_reg = &(vcpu->arch.shadow_dbg_reg);
+	u32 dbsr = vcpu->arch.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 = dbg_reg->dac1;
+		else if (dbsr & (DBSR_DAC2R | DBSR_DAC2W))
+			run->debug.arch.address = dbg_reg->dac2;
+	}
+
+	return RESUME_HOST;
+}
+
 static void kvmppc_fill_pt_regs(struct pt_regs *regs)
 {
 	ulong r1, ip, msr, lr;
@@ -819,6 +877,11 @@ static void kvmppc_restart_interrupt(struct kvm_vcpu *vcpu,
 	case BOOKE_INTERRUPT_CRITICAL:
 		unknown_exception(&regs);
 		break;
+	case BOOKE_INTERRUPT_DEBUG:
+		/* Save DBSR before preemption is enabled */
+		vcpu->arch.dbsr = mfspr(SPRN_DBSR);
+		kvmppc_clear_dbsr();
+		break;
 	}
 }
 
@@ -1118,18 +1181,10 @@ 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;
 	}
 
@@ -1180,7 +1235,7 @@ 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
@@ -1557,12 +1612,6 @@ 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;
@@ -1668,6 +1717,157 @@ void kvmppc_decrementer_func(unsigned long data)
 	kvmppc_set_tsr_bits(vcpu, TSR_DIS);
 }
 
+static int kvmppc_booke_add_breakpoint(struct debug_reg *dbg_reg,
+				       uint64_t addr, int index)
+{
+	switch (index) {
+	case 0:
+		dbg_reg->dbcr0 |= DBCR0_IAC1;
+		dbg_reg->iac1 = addr;
+		break;
+	case 1:
+		dbg_reg->dbcr0 |= DBCR0_IAC2;
+		dbg_reg->iac2 = addr;
+		break;
+#if CONFIG_PPC_ADV_DEBUG_IACS > 2
+	case 2:
+		dbg_reg->dbcr0 |= DBCR0_IAC3;
+		dbg_reg->iac3 = addr;
+		break;
+	case 3:
+		dbg_reg->dbcr0 |= DBCR0_IAC4;
+		dbg_reg->iac4 = addr;
+		break;
+#endif
+	default:
+		return -EINVAL;
+	}
+
+	dbg_reg->dbcr0 |= DBCR0_IDM;
+	return 0;
+}
+
+static int kvmppc_booke_add_watchpoint(struct debug_reg *dbg_reg, uint64_t addr,
+				       int type, int index)
+{
+	switch (index) {
+	case 0:
+		if (type & KVMPPC_DEBUG_WATCH_READ)
+			dbg_reg->dbcr0 |= DBCR0_DAC1R;
+		if (type & KVMPPC_DEBUG_WATCH_WRITE)
+			dbg_reg->dbcr0 |= DBCR0_DAC1W;
+		dbg_reg->dac1 = addr;
+		break;
+	case 1:
+		if (type & KVMPPC_DEBUG_WATCH_READ)
+			dbg_reg->dbcr0 |= DBCR0_DAC2R;
+		if (type & KVMPPC_DEBUG_WATCH_WRITE)
+			dbg_reg->dbcr0 |= DBCR0_DAC2W;
+		dbg_reg->dac2 = addr;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	dbg_reg->dbcr0 |= DBCR0_IDM;
+	return 0;
+}
+void kvm_guest_protect_msr(struct kvm_vcpu *vcpu, ulong prot_bitmap, bool set)
+{
+	/* XXX: Add similar MSR protection for BookE-PR */
+#ifdef CONFIG_KVM_BOOKE_HV
+	BUG_ON(prot_bitmap & ~(MSRP_UCLEP | MSRP_DEP | MSRP_PMMP));
+	if (set) {
+		if (prot_bitmap & MSR_UCLE)
+			vcpu->arch.shadow_msrp |= MSRP_UCLEP;
+		if (prot_bitmap & MSR_DE)
+			vcpu->arch.shadow_msrp |= MSRP_DEP;
+		if (prot_bitmap & MSR_PMM)
+			vcpu->arch.shadow_msrp |= MSRP_PMMP;
+	} else {
+		if (prot_bitmap & MSR_UCLE)
+			vcpu->arch.shadow_msrp &= ~MSRP_UCLEP;
+		if (prot_bitmap & MSR_DE)
+			vcpu->arch.shadow_msrp &= ~MSRP_DEP;
+		if (prot_bitmap & MSR_PMM)
+			vcpu->arch.shadow_msrp &= ~MSRP_PMMP;
+	}
+#endif
+}
+
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					 struct kvm_guest_debug *dbg)
+{
+	struct debug_reg *dbg_reg;
+	int n, b = 0, w = 0;
+
+	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
+		vcpu->arch.shadow_dbg_reg.dbcr0 = 0;
+		vcpu->guest_debug = 0;
+		kvm_guest_protect_msr(vcpu, MSR_DE, false);
+		return 0;
+	}
+
+	kvm_guest_protect_msr(vcpu, MSR_DE, true);
+	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;
+
+	/* Code below handles only HW breakpoints */
+	dbg_reg = &(vcpu->arch.shadow_dbg_reg);
+
+#ifdef CONFIG_KVM_BOOKE_HV
+	/*
+	 * On BookE-HV (e500mc) the guest is always executed with MSR.GS=1
+	 * DBCR1 and DBCR2 are set to trigger debug events when MSR.PR is 0
+	 */
+	dbg_reg->dbcr1 = 0;
+	dbg_reg->dbcr2 = 0;
+#else
+	/*
+	 * On BookE-PR (e500v2) the guest is always executed with MSR.PR=1
+	 * We set DBCR1 and DBCR2 to only trigger debug events when MSR.PR
+	 * is set.
+	 */
+	dbg_reg->dbcr1 = DBCR1_IAC1US | DBCR1_IAC2US | DBCR1_IAC3US |
+			  DBCR1_IAC4US;
+	dbg_reg->dbcr2 = DBCR2_DAC1US | DBCR2_DAC2US;
+#endif
+
+	if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))
+		return 0;
+
+	for (n = 0; n < (KVMPPC_BOOKE_IAC_NUM + KVMPPC_BOOKE_DAC_NUM); n++) {
+		uint64_t addr = dbg->arch.bp[n].addr;
+		uint32_t type = dbg->arch.bp[n].type;
+
+		if (type == KVMPPC_DEBUG_NONE)
+			continue;
+
+		if (type & !(KVMPPC_DEBUG_WATCH_READ |
+			     KVMPPC_DEBUG_WATCH_WRITE |
+			     KVMPPC_DEBUG_BREAKPOINT))
+			return -EINVAL;
+
+		if (type & KVMPPC_DEBUG_BREAKPOINT) {
+			/* Setting H/W breakpoint */
+			if (kvmppc_booke_add_breakpoint(dbg_reg, addr, b++))
+				return -EINVAL;
+		} else {
+			/* Setting H/W watchpoint */
+			if (kvmppc_booke_add_watchpoint(dbg_reg, addr,
+							type, w++))
+				return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 void kvmppc_booke_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 	vcpu->cpu = smp_processor_id();
@@ -1678,6 +1878,9 @@ void kvmppc_booke_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	current->thread.kvm_vcpu = NULL;
 	vcpu->cpu = -1;
+
+	/* Clear pending debug event in DBSR */
+	kvmppc_clear_dbsr();
 }
 
 int __init kvmppc_booke_init(void)
diff --git a/arch/powerpc/kvm/booke.h b/arch/powerpc/kvm/booke.h
index 5fd1ba6..a1ff67d 100644
--- a/arch/powerpc/kvm/booke.h
+++ b/arch/powerpc/kvm/booke.h
@@ -129,4 +129,9 @@ static inline void kvmppc_save_guest_fp(struct kvm_vcpu *vcpu)
 		giveup_fpu(current);
 #endif
 }
+
+static inline void kvmppc_clear_dbsr(void)
+{
+	mtspr(SPRN_DBSR, mfspr(SPRN_DBSR));
+}
 #endif /* __KVM_BOOKE_H__ */
-- 
1.7.0.4

Re: [PATCH 0/4 v6] KVM :PPC: Userspace Debug support

[Alexander Graf]

On 04.07.2013, at 08:57, Bharat Bhushan wrote:

> From: Bharat Bhushan <bharat.bhushan@freescale.com>
>=20
> Note: These patches depends on https://lkml.org/lkml/2013/7/4/49.
>=20
> This patchset adds the userspace debug support for booke/bookehv.
> this is tested on powerpc e500v2/e500mc devices.

Thanks, applied to kvm-ppc-queue.


Alex

>=20
> We are now assuming that debug resource will not be used by kernel for
> its own debugging. It will be used for only kernel user process =
debugging.
> So the kernel debug load interface during context_to is used to load
> debug conext for that selected process.
>=20
> v5->v6
> - Earlier it was a patchset of six patches. Now this is devided into
>   two parts: 1) powerpc spcific changes 2) kvm specific changes.
>   This patchset now contains only KVM specific changes.
> - using "ehpriv 1" (earlier using "ehpriv") for software breakpoint
> -
>=20
> v4->v5
> - Some comments reworded and other cleanup (like change of function =
name etc)
> - Added a function for setting MSRP rather than inline
>=20
> v3->v4
> - 4 out of 7 patches of initial patchset were applied.
>   This patchset is on and above those 4 patches
> - KVM local "struct kvmppc_booke_debug_reg" is replaced by
>   powerpc global "struct debug_reg"
> - use switch_booke_debug_regs() for debug register context switch.
> - Save DBSR before kernel pre-emption is enabled.
> - Some more cleanup
>=20
> v2->v3
> - We are now assuming that debug resource will not be used by
>   kernel for its own debugging.
>   It will be used for only kernel user process debugging.
>   So the kernel debug load interface during context_to is
>   used to load debug conext for that selected process.
>=20
> v1->v2
> - Debug registers are save/restore in vcpu_put/vcpu_get.
>   Earlier the debug registers are saved/restored in guest entry/exit
>=20
> Bharat Bhushan (4):
>  powerpc: export debug registers save function for KVM
>  KVM: PPC: exit to user space on "ehpriv 1" instruction
>  KVM: PPC: Using "struct debug_reg"
>  KVM: PPC: Add userspace debug stub support
>=20
> arch/powerpc/include/asm/disassemble.h |    4 +
> arch/powerpc/include/asm/kvm_booke.h   |    7 +-
> arch/powerpc/include/asm/kvm_host.h    |   16 +--
> arch/powerpc/include/asm/switch_to.h   |    1 +
> arch/powerpc/include/uapi/asm/kvm.h    |   22 ++-
> arch/powerpc/kernel/process.c          |    3 +-
> arch/powerpc/kvm/booke.c               |  275 =
++++++++++++++++++++++++++++----
> arch/powerpc/kvm/booke.h               |    5 +
> arch/powerpc/kvm/e500_emulate.c        |   26 +++
> 9 files changed, 312 insertions(+), 47 deletions(-)
>=20
>=20