[PATCH v2 10/10] KVM: arm64: add trace points for guest_debug debug

Alex Bennée
2015-03-31T15:25:36Z

This includes trace points for:
kvm_arch_setup_guest_debug
kvm_arch_clear_guest_debug
kvm_handle_guest_debug

I've also added some generic register setting trace events so I can
watch the register values being built up over time. The local
dump_dbg_regs() function dumps all the HW BKPT and WPT registers.

I've also added a #define trace_dreg to shorten some lines.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 638c111..7c96288 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -25,12 +25,37 @@
#include <asm/kvm_host.h>
#include <asm/kvm_emulate.h>

+#include "trace.h"
+
+#define trace_dreg(name, value) trace_kvm_arch_setup_debug_reg32(name, value)
+
/* These are the bits of MDSCR_EL1 we may mess with */
#define MDSCR_EL1_DEBUG_BITS (DBG_MDSCR_SS | \
DBG_MDSCR_KDE | \
DBG_MDSCR_MDE)

/**
+ * dump_dbg_regs - simple debug helper
+ *
+ * This provides a simple helper to dump the HW debug registers
+ */
+static void dump_dbg_regs(struct kvm_vcpu *vcpu, int nb, int nw)
+{
+ int i;
+
+ for (i = 0; i < nb; i++) {
+ trace_printk("bkpt%d: 0x%08x:0x%llx\n", i,
+ (u32) vcpu_sys_reg(vcpu, DBGBCR0_EL1 + i),
+ vcpu_sys_reg(vcpu, DBGBVR0_EL1 + i));
+ }
+ for (i = 0; i < nb; i++) {
+ trace_printk("wtpt%d: 0x%08x:0x%llx\n", i,
+ (u32) vcpu_sys_reg(vcpu, DBGWCR0_EL1 + i),
+ vcpu_sys_reg(vcpu, DBGWVR0_EL1 + i));
+ }
+}
+
+/**
* kvm_arch_setup_debug - set-up debug related stuff
*
* @vcpu: the vcpu pointer
@@ -52,9 +77,13 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu)
{
bool trap_debug = false;

+ trace_kvm_arch_setup_debug(vcpu->guest_debug);
+
vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | MDCR_EL2_TPMCR);
vcpu->arch.mdcr_el2 |= (MDCR_EL2_TDRA | MDCR_EL2_TDOSA);

+ trace_kvm_arch_setup_debug_reg32("MDCR_EL2", vcpu->arch.mdcr_el2);
+
/*
* If we are not treating debug registers are dirty we need
* to trap if the guest starts accessing them.
@@ -66,6 +95,8 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu)
if (vcpu->guest_debug) {
vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;

+ trace_dreg("MDCR_EL2", vcpu->arch.mdcr_el2);
+
/* Save pstate/mdscr */
vcpu_debug_saved_reg(vcpu, pstate_ss_bit) =
*vcpu_cpsr(vcpu) & DBG_SPSR_SS;
@@ -73,6 +104,11 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu)
vcpu_debug_saved_reg(vcpu, mdscr_el1) =
vcpu_sys_reg(vcpu, MDSCR_EL1);

+ trace_dreg("Save: PSTATE.SS",
+ vcpu_debug_saved_reg(vcpu, pstate_ss_bit));
+ trace_dreg("Save: MDSCR",
+ vcpu_debug_saved_reg(vcpu, mdscr_el1));
+
/*
* Single Step (ARM ARM D2.12.3 The software step state
* machine)
@@ -88,6 +124,8 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu)
*vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
}
+ trace_dreg("SPSR_EL2", *vcpu_cpsr(vcpu));
+ trace_dreg("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));

/*
* HW Break/Watch points
@@ -136,6 +174,9 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu)
&host->dbg_wvr,
sizeof(__u64)*nw);

+ if (trace_kvm_arch_setup_debug_reg32_enabled())
+ dump_dbg_regs(vcpu, nb, nw);
+
/* Make sure hyp.S copies them in/out */
vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
/* Also track guest changes */
@@ -147,15 +188,24 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu)
vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE;
}

+ trace_kvm_arch_setup_debug_reg32("MDCR_EL2", vcpu->arch.mdcr_el2);
+ trace_kvm_arch_setup_debug_reg32("MDSCR_EL1",
+ vcpu_sys_reg(vcpu, MDSCR_EL1));
+
+
/* Trap debug register access? */
if (trap_debug)
vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
else
vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDA;
+
+ trace_kvm_arch_setup_debug_reg32("MDCR_EL2", vcpu->arch.mdcr_el2);
}

void kvm_arch_clear_debug(struct kvm_vcpu *vcpu)
{
+ trace_kvm_arch_clear_debug(vcpu->guest_debug);
+
if (vcpu->guest_debug) {
/* Restore pstate/mdscr bits we may have messed with */
*vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
@@ -164,6 +214,8 @@ void kvm_arch_clear_debug(struct kvm_vcpu *vcpu)
vcpu_sys_reg(vcpu, MDSCR_EL1) =
vcpu_debug_saved_reg(vcpu, mdscr_el1);

+ trace_dreg("SPSR_EL2", *vcpu_cpsr(vcpu));
+ trace_dreg("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
/*
* If we were using HW debug we need to restore the
* values the guest had set them up with
@@ -188,6 +240,10 @@ void kvm_arch_clear_debug(struct kvm_vcpu *vcpu)
memcpy(&vcpu_sys_reg(vcpu, DBGWVR0_EL1),
&regs->dbg_wvr,
sizeof(__u64)*nw);
+
+ if (trace_kvm_arch_setup_debug_reg32_enabled())
+ dump_dbg_regs(vcpu, nb, nw);
+
}
}
}
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 460a1aa..c6cc69a 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -97,6 +97,8 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
u32 hsr = kvm_vcpu_get_hsr(vcpu);

+ trace_kvm_handle_guest_debug(*vcpu_pc(vcpu), hsr);
+
run->exit_reason = KVM_EXIT_DEBUG;
run->debug.arch.hsr = hsr;

diff --git a/arch/arm64/kvm/trace.h b/arch/arm64/kvm/trace.h
index 157416e9..dffdb49 100644
--- a/arch/arm64/kvm/trace.h
+++ b/arch/arm64/kvm/trace.h
@@ -44,6 +44,72 @@ TRACE_EVENT(kvm_hvc_arm64,
__entry->vcpu_pc, __entry->r0, __entry->imm)
);

+TRACE_EVENT(kvm_handle_guest_debug,
+ TP_PROTO(unsigned long vcpu_pc, u32 hsr),
+ TP_ARGS(vcpu_pc, hsr),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, vcpu_pc)
+ __field(u32, hsr)
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu_pc = vcpu_pc;
+ __entry->hsr = hsr;
+ ),
+
+ TP_printk("debug exception at 0x%08lx (HSR: 0x%08x)",
+ __entry->vcpu_pc, __entry->hsr)
+);
+
+
+TRACE_EVENT(kvm_arch_setup_debug,
+ TP_PROTO(__u32 guest_debug),
+ TP_ARGS(guest_debug),
+
+ TP_STRUCT__entry(
+ __field(__u32, guest_debug)
+ ),
+
+ TP_fast_assign(
+ __entry->guest_debug = guest_debug;
+ ),
+
+ TP_printk("flags: 0x%08x", __entry->guest_debug)
+);
+
+TRACE_EVENT(kvm_arch_clear_debug,
+ TP_PROTO(__u32 guest_debug),
+ TP_ARGS(guest_debug),
+
+ TP_STRUCT__entry(
+ __field(__u32, guest_debug)
+ ),
+
+ TP_fast_assign(
+ __entry->guest_debug = guest_debug;
+ ),
+
+ TP_printk("flags: 0x%08x", __entry->guest_debug)
+);
+
+TRACE_EVENT(kvm_arch_setup_debug_reg32,
+ TP_PROTO(const char *name, __u32 value),
+ TP_ARGS(name, value),
+
+ TP_STRUCT__entry(
+ __field(const char *, name)
+ __field(__u32, value)
+ ),
+
+ TP_fast_assign(
+ __entry->name = name;
+ __entry->value = value;
+ ),
+
+ TP_printk("%s now 0x%08x", __entry->name, __entry->value)
+);
+
#endif /* _TRACE_ARM64_KVM_H */

#undef TRACE_INCLUDE_PATH
--
2.3.4

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