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@google.com>
---
 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);
 }
-- 
2.33.0.464.g1972c5931b-goog

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@google.com>
> ---
>   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@redhat.com>