Commit 1c343051 authored by Sean Christopherson's avatar Sean Christopherson Committed by Peter Zijlstra
Browse files

perf: Add wrappers for invoking guest callbacks 



Add helpers for the guest callbacks to prepare for burying the callbacks
behind a Kconfig (it's a lot easier to provide a few stubs than to #ifdef
piles of code), and also to prepare for converting the callbacks to
static_call().  perf_instruction_pointer() in particular will have subtle
semantics with static_call(), as the "no callbacks" case will return 0 if
the callbacks are unregistered between querying guest state and getting
the IP.  Implement the change now to avoid a functional change when adding
static_call() support, and because the new helper needs to return
_something_ in this case.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-8-seanjc@google.com
parent b9f5621c

arch/arm64/kernel/perf_callchain.c

+5 −11
Original line number Diff line number Diff line
@@ -102,9 +102,7 @@ compat_user_backtrace(struct compat_frame_tail __user *tail, 
void perf_callchain_user(struct perf_callchain_entry_ctx *entry,

			 struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();



	if (guest_cbs && guest_cbs->state()) {

	if (perf_guest_state()) {

		/* We don't support guest os callchain now */

		return;

	}
@@ -149,10 +147,9 @@ static bool callchain_trace(void *data, unsigned long pc) 
void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,

			   struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();

	struct stackframe frame;



	if (guest_cbs && guest_cbs->state()) {

	if (perf_guest_state()) {

		/* We don't support guest os callchain now */

		return;

	}
@@ -163,18 +160,15 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, 


unsigned long perf_instruction_pointer(struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();



	if (guest_cbs && guest_cbs->state())

		return guest_cbs->get_ip();

	if (perf_guest_state())

		return perf_guest_get_ip();



	return instruction_pointer(regs);

}



unsigned long perf_misc_flags(struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();

	unsigned int guest_state = guest_cbs ? guest_cbs->state() : 0;

	unsigned int guest_state = perf_guest_state();

	int misc = 0;



	if (guest_state) {

arch/x86/events/core.c

+5 −10
Original line number Diff line number Diff line
@@ -2768,11 +2768,10 @@ static bool perf_hw_regs(struct pt_regs *regs) 
void

perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();

	struct unwind_state state;

	unsigned long addr;



	if (guest_cbs && guest_cbs->state()) {

	if (perf_guest_state()) {

		/* TODO: We don't support guest os callchain now */

		return;

	}
@@ -2872,11 +2871,10 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent 
void

perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();

	struct stack_frame frame;

	const struct stack_frame __user *fp;



	if (guest_cbs && guest_cbs->state()) {

	if (perf_guest_state()) {

		/* TODO: We don't support guest os callchain now */

		return;

	}
@@ -2953,18 +2951,15 @@ static unsigned long code_segment_base(struct pt_regs *regs) 


unsigned long perf_instruction_pointer(struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();



	if (guest_cbs && guest_cbs->state())

		return guest_cbs->get_ip();

	if (perf_guest_state())

		return perf_guest_get_ip();



	return regs->ip + code_segment_base(regs);

}



unsigned long perf_misc_flags(struct pt_regs *regs)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();

	unsigned int guest_state = guest_cbs ? guest_cbs->state() : 0;

	unsigned int guest_state = perf_guest_state();

	int misc = 0;



	if (guest_state) {

arch/x86/events/intel/core.c

+1 −4
Original line number Diff line number Diff line
@@ -2837,7 +2837,6 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status) 
{

	struct perf_sample_data data;

	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

	struct perf_guest_info_callbacks *guest_cbs;

	int bit;

	int handled = 0;

	u64 intel_ctrl = hybrid(cpuc->pmu, intel_ctrl);
@@ -2904,9 +2903,7 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status) 
	 */

	if (__test_and_clear_bit(GLOBAL_STATUS_TRACE_TOPAPMI_BIT, (unsigned long *)&status)) {

		handled++;



		guest_cbs = perf_get_guest_cbs();

		if (likely(!guest_cbs || !guest_cbs->handle_intel_pt_intr()))

		if (!perf_guest_handle_intel_pt_intr())

			intel_pt_interrupt();

	}

include/linux/perf_event.h

+24 −0
Original line number Diff line number Diff line
@@ -1254,6 +1254,30 @@ static inline struct perf_guest_info_callbacks *perf_get_guest_cbs(void) 
	 */

	return rcu_dereference(perf_guest_cbs);

}

static inline unsigned int perf_guest_state(void)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();



	return guest_cbs ? guest_cbs->state() : 0;

}

static inline unsigned long perf_guest_get_ip(void)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();



	/*

	 * Arbitrarily return '0' in the unlikely scenario that the callbacks

	 * are unregistered between checking guest state and getting the IP.

	 */

	return guest_cbs ? guest_cbs->get_ip() : 0;

}

static inline unsigned int perf_guest_handle_intel_pt_intr(void)

{

	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();



	if (guest_cbs && guest_cbs->handle_intel_pt_intr)

		return guest_cbs->handle_intel_pt_intr();

	return 0;

}

extern void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);

extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);