Re: [PATCH v3 05/16] perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv

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On 22/09/21 02:05, Sean Christopherson wrote:
Drop "support" for guest callbacks from architctures that don't implement
the guest callbacks.  Future patches will convert the callbacks to
static_call; rather than churn a bunch of arch code (that was presumably
copy+pasted from x86), remove it wholesale as it's useless and at best
wasting cycles.

A future patch will also add a Kconfig to force architcture to opt into
the callbacks to make it more difficult for uses "support" to sneak in in
the future.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
  arch/arm/kernel/perf_callchain.c   | 33 ++++-------------------------
  arch/csky/kernel/perf_callchain.c  | 12 -----------
  arch/nds32/kernel/perf_event_cpu.c | 34 ++++--------------------------
  arch/riscv/kernel/perf_callchain.c | 13 ------------
  4 files changed, 8 insertions(+), 84 deletions(-)

diff --git a/arch/arm/kernel/perf_callchain.c b/arch/arm/kernel/perf_callchain.c
index 1626dfc6f6ce..bc6b246ab55e 100644
--- a/arch/arm/kernel/perf_callchain.c
+++ b/arch/arm/kernel/perf_callchain.c
@@ -62,14 +62,8 @@ user_backtrace(struct 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();
  	struct frame_tail __user *tail;
- if (guest_cbs && guest_cbs->is_in_guest()) {
-		/* We don't support guest os callchain now */
-		return;
-	}
-
  	perf_callchain_store(entry, regs->ARM_pc);
if (!current->mm)
@@ -99,44 +93,25 @@ callchain_trace(struct stackframe *fr,
  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 fr;
- if (guest_cbs && guest_cbs->is_in_guest()) {
-		/* We don't support guest os callchain now */
-		return;
-	}
-
  	arm_get_current_stackframe(regs, &fr);
  	walk_stackframe(&fr, callchain_trace, 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->is_in_guest())
-		return guest_cbs->get_guest_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();
  	int misc = 0;
- if (guest_cbs && guest_cbs->is_in_guest()) {
-		if (guest_cbs->is_user_mode())
-			misc |= PERF_RECORD_MISC_GUEST_USER;
-		else
-			misc |= PERF_RECORD_MISC_GUEST_KERNEL;
-	} else {
-		if (user_mode(regs))
-			misc |= PERF_RECORD_MISC_USER;
-		else
-			misc |= PERF_RECORD_MISC_KERNEL;
-	}
+	if (user_mode(regs))
+		misc |= PERF_RECORD_MISC_USER;
+	else
+		misc |= PERF_RECORD_MISC_KERNEL;
return misc;
  }
diff --git a/arch/csky/kernel/perf_callchain.c b/arch/csky/kernel/perf_callchain.c
index 35318a635a5f..92057de08f4f 100644
--- a/arch/csky/kernel/perf_callchain.c
+++ b/arch/csky/kernel/perf_callchain.c
@@ -86,13 +86,8 @@ static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
  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();
  	unsigned long fp = 0;
- /* C-SKY does not support virtualization. */
-	if (guest_cbs && guest_cbs->is_in_guest())
-		return;
-
  	fp = regs->regs[4];
  	perf_callchain_store(entry, regs->pc);
@@ -111,15 +106,8 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
  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 fr;
- /* C-SKY does not support virtualization. */
-	if (guest_cbs && guest_cbs->is_in_guest()) {
-		pr_warn("C-SKY does not support perf in guest mode!");
-		return;
-	}
-
  	fr.fp = regs->regs[4];
  	fr.lr = regs->lr;
  	walk_stackframe(&fr, entry);
diff --git a/arch/nds32/kernel/perf_event_cpu.c b/arch/nds32/kernel/perf_event_cpu.c
index f38791960781..a78a879e7ef1 100644
--- a/arch/nds32/kernel/perf_event_cpu.c
+++ b/arch/nds32/kernel/perf_event_cpu.c
@@ -1363,7 +1363,6 @@ 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();
  	unsigned long fp = 0;
  	unsigned long gp = 0;
  	unsigned long lp = 0;
@@ -1372,11 +1371,6 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry,
leaf_fp = 0; - if (guest_cbs && guest_cbs->is_in_guest()) {
-		/* We don't support guest os callchain now */
-		return;
-	}
-
  	perf_callchain_store(entry, regs->ipc);
  	fp = regs->fp;
  	gp = regs->gp;
@@ -1480,13 +1474,8 @@ 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 fr;
- if (guest_cbs && guest_cbs->is_in_guest()) {
-		/* We don't support guest os callchain now */
-		return;
-	}
  	fr.fp = regs->fp;
  	fr.lp = regs->lp;
  	fr.sp = regs->sp;
@@ -1495,32 +1484,17 @@ 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();
-
-	/* However, NDS32 does not support virtualization */
-	if (guest_cbs && guest_cbs->is_in_guest())
-		return guest_cbs->get_guest_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();
  	int misc = 0;
- /* However, NDS32 does not support virtualization */
-	if (guest_cbs && guest_cbs->is_in_guest()) {
-		if (guest_cbs->is_user_mode())
-			misc |= PERF_RECORD_MISC_GUEST_USER;
-		else
-			misc |= PERF_RECORD_MISC_GUEST_KERNEL;
-	} else {
-		if (user_mode(regs))
-			misc |= PERF_RECORD_MISC_USER;
-		else
-			misc |= PERF_RECORD_MISC_KERNEL;
-	}
+	if (user_mode(regs))
+		misc |= PERF_RECORD_MISC_USER;
+	else
+		misc |= PERF_RECORD_MISC_KERNEL;
return misc;
  }
diff --git a/arch/riscv/kernel/perf_callchain.c b/arch/riscv/kernel/perf_callchain.c
index 8ecfc4c128bc..1fc075b8f764 100644
--- a/arch/riscv/kernel/perf_callchain.c
+++ b/arch/riscv/kernel/perf_callchain.c
@@ -56,13 +56,8 @@ static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
  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();
  	unsigned long fp = 0;
- /* RISC-V does not support perf in guest mode. */
-	if (guest_cbs && guest_cbs->is_in_guest())
-		return;
-
  	fp = regs->s0;
  	perf_callchain_store(entry, regs->epc);
@@ -79,13 +74,5 @@ static bool fill_callchain(void *entry, 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();
-
-	/* RISC-V does not support perf in guest mode. */
-	if (guest_cbs && guest_cbs->is_in_guest()) {
-		pr_warn("RISC-V does not support perf in guest mode!");
-		return;
-	}
-
  	walk_stackframe(NULL, regs, fill_callchain, entry);
  }


Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>




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