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KVM: arm64: Remove debug tracepoints
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The debug tracepoints are a useless firehose of information that track
implementation detail rather than well-defined events. These are going
to be rather difficult to uphold now that the implementation is getting
redone, so throw them out instead of bending over backwards.

Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241219224116.3941496-10-oliver.upton@linux.dev
[maz: fixed compilation after trace-ectomy]
Signed-off-by: Marc Zyngier <maz@kernel.org>
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Oliver Upton authored and Marc Zyngier committed Dec 20, 2024
1 parent 58db67e commit 3b77809
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Showing 3 changed files with 0 additions and 120 deletions.
34 changes: 0 additions & 34 deletions arch/arm64/kvm/debug.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@
#include <asm/kvm_arm.h>
#include <asm/kvm_emulate.h>

#include "trace.h"

/*
* save/restore_guest_debug_regs
Expand All @@ -35,10 +34,6 @@ static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
u64 val = vcpu_read_sys_reg(vcpu, MDSCR_EL1);

vcpu->arch.guest_debug_preserved.mdscr_el1 = val;

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);
}
Expand All @@ -49,9 +44,6 @@ static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)

vcpu_write_sys_reg(vcpu, val, MDSCR_EL1);

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
Expand Down Expand Up @@ -110,8 +102,6 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);

preempt_enable();

trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
}

/**
Expand Down Expand Up @@ -158,8 +148,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
{
unsigned long mdscr;

trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);

kvm_arm_setup_mdcr_el2(vcpu);

/* Check if we need to use the debug registers. */
Expand Down Expand Up @@ -209,8 +197,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
}

trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));

/*
* HW Breakpoints and watchpoints
*
Expand All @@ -228,14 +214,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
vcpu_set_flag(vcpu, DEBUG_DIRTY);

trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
&vcpu->arch.debug_ptr->dbg_bcr[0],
&vcpu->arch.debug_ptr->dbg_bvr[0]);

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
Expand All @@ -257,14 +235,10 @@ 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_set_flag(vcpu, DEBUG_DIRTY);

trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
}

void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
{
trace_kvm_arm_clear_debug(vcpu->guest_debug);

/*
* Restore the guest's debug registers if we were using them.
*/
Expand All @@ -286,14 +260,6 @@ void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
*/
if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
kvm_arm_reset_debug_ptr(vcpu);

trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
&vcpu->arch.debug_ptr->dbg_bcr[0],
&vcpu->arch.debug_ptr->dbg_bvr[0]);

trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
&vcpu->arch.debug_ptr->dbg_wcr[0],
&vcpu->arch.debug_ptr->dbg_wvr[0]);
}
}
}
Expand Down
11 changes: 0 additions & 11 deletions arch/arm64/kvm/sys_regs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -657,8 +657,6 @@ static bool trap_debug_regs(struct kvm_vcpu *vcpu,
vcpu_set_flag(vcpu, DEBUG_DIRTY);

kvm_debug_set_guest_ownership(vcpu);
trace_trap_reg(__func__, r->reg, p->is_write, p->regval);

return true;
}

Expand Down Expand Up @@ -711,8 +709,6 @@ static bool trap_bvr(struct kvm_vcpu *vcpu,
else
dbg_to_reg(vcpu, p, rd, dbg_reg);

trace_trap_reg(__func__, rd->CRm, p->is_write, *dbg_reg);

return true;
}

Expand Down Expand Up @@ -748,8 +744,6 @@ static bool trap_bcr(struct kvm_vcpu *vcpu,
else
dbg_to_reg(vcpu, p, rd, dbg_reg);

trace_trap_reg(__func__, rd->CRm, p->is_write, *dbg_reg);

return true;
}

Expand Down Expand Up @@ -785,9 +779,6 @@ static bool trap_wvr(struct kvm_vcpu *vcpu,
else
dbg_to_reg(vcpu, p, rd, dbg_reg);

trace_trap_reg(__func__, rd->CRm, p->is_write,
vcpu->arch.vcpu_debug_state.dbg_wvr[rd->CRm]);

return true;
}

Expand Down Expand Up @@ -823,8 +814,6 @@ static bool trap_wcr(struct kvm_vcpu *vcpu,
else
dbg_to_reg(vcpu, p, rd, dbg_reg);

trace_trap_reg(__func__, rd->CRm, p->is_write, *dbg_reg);

return true;
}

Expand Down
75 changes: 0 additions & 75 deletions arch/arm64/kvm/trace_handle_exit.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -46,38 +46,6 @@ TRACE_EVENT(kvm_hvc_arm64,
__entry->vcpu_pc, __entry->r0, __entry->imm)
);

TRACE_EVENT(kvm_arm_setup_debug,
TP_PROTO(struct kvm_vcpu *vcpu, __u32 guest_debug),
TP_ARGS(vcpu, guest_debug),

TP_STRUCT__entry(
__field(struct kvm_vcpu *, vcpu)
__field(__u32, guest_debug)
),

TP_fast_assign(
__entry->vcpu = vcpu;
__entry->guest_debug = guest_debug;
),

TP_printk("vcpu: %p, flags: 0x%08x", __entry->vcpu, __entry->guest_debug)
);

TRACE_EVENT(kvm_arm_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)
);

/*
* The dreg32 name is a leftover from a distant past. This will really
* output a 64bit value...
Expand All @@ -99,49 +67,6 @@ TRACE_EVENT(kvm_arm_set_dreg32,
TP_printk("%s: 0x%llx", __entry->name, __entry->value)
);

TRACE_DEFINE_SIZEOF(__u64);

TRACE_EVENT(kvm_arm_set_regset,
TP_PROTO(const char *type, int len, __u64 *control, __u64 *value),
TP_ARGS(type, len, control, value),
TP_STRUCT__entry(
__field(const char *, name)
__field(int, len)
__array(u64, ctrls, 16)
__array(u64, values, 16)
),
TP_fast_assign(
__entry->name = type;
__entry->len = len;
memcpy(__entry->ctrls, control, len << 3);
memcpy(__entry->values, value, len << 3);
),
TP_printk("%d %s CTRL:%s VALUE:%s", __entry->len, __entry->name,
__print_array(__entry->ctrls, __entry->len, sizeof(__u64)),
__print_array(__entry->values, __entry->len, sizeof(__u64)))
);

TRACE_EVENT(trap_reg,
TP_PROTO(const char *fn, int reg, bool is_write, u64 write_value),
TP_ARGS(fn, reg, is_write, write_value),

TP_STRUCT__entry(
__field(const char *, fn)
__field(int, reg)
__field(bool, is_write)
__field(u64, write_value)
),

TP_fast_assign(
__entry->fn = fn;
__entry->reg = reg;
__entry->is_write = is_write;
__entry->write_value = write_value;
),

TP_printk("%s %s reg %d (0x%016llx)", __entry->fn, __entry->is_write?"write to":"read from", __entry->reg, __entry->write_value)
);

TRACE_EVENT(kvm_handle_sys_reg,
TP_PROTO(unsigned long hsr),
TP_ARGS(hsr),
Expand Down

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