On Sun, Jul 13, 2025 at 07:17:00AM -0600, Theo de Raadt wrote:
> David Gwynne <david@gwynne.id.au> wrote:
> 
> > we just went through an effort to shrink kernel code to help the install media fit. it seems a bit ungrateful to use those bytes again for something that's generally only going to be used for performance monitoring.
> 
> Nope, that's not a good reason at all.  Prefer not to trade tons of cpp
> conditionals all over the place, for having more very different kernel
> execution behaviours.
> 
> OTOH, it will take some time to get this into all the architectures.  Once
> that's done, this should become a baseline feature.  Only then can MI code
> call it.   Providing it behind an #ifdef means that it should not be called
> from inside an #ifdef.

ok. how about hanging xcall off an archs cpu device until they're all
implemented, and not providing "xcall.h" so we can't have
#if NXCALL > 0?

Index: arch/amd64/amd64/cpu.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/cpu.c,v
diff -u -p -r1.196 cpu.c
--- arch/amd64/amd64/cpu.c	5 Jun 2025 09:29:54 -0000	1.196
+++ arch/amd64/amd64/cpu.c	14 Jul 2025 05:07:42 -0000
@@ -637,6 +637,8 @@ cpu_attach(struct device *parent, struct
 #endif
 
 #if defined(MULTIPROCESSOR)
+	cpu_xcall_establish(ci);
+
 	/*
 	 * Allocate UPAGES contiguous pages for the idle PCB and stack.
 	 */
Index: arch/amd64/amd64/ipifuncs.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/ipifuncs.c,v
diff -u -p -r1.39 ipifuncs.c
--- arch/amd64/amd64/ipifuncs.c	7 Jun 2024 16:53:35 -0000	1.39
+++ arch/amd64/amd64/ipifuncs.c	14 Jul 2025 05:07:42 -0000
@@ -108,6 +108,7 @@ void (*ipifunc[X86_NIPI])(struct cpu_inf
 	NULL,
 #endif
 	x86_64_ipi_wbinvd,
+	cpu_xcall_dispatch,
 };
 
 void
Index: arch/amd64/include/cpu.h
===================================================================
RCS file: /cvs/src/sys/arch/amd64/include/cpu.h,v
diff -u -p -r1.180 cpu.h
--- arch/amd64/include/cpu.h	28 Apr 2025 16:18:25 -0000	1.180
+++ arch/amd64/include/cpu.h	14 Jul 2025 05:07:42 -0000
@@ -53,6 +53,7 @@
 #include <sys/sched.h>
 #include <sys/sensors.h>
 #include <sys/srp.h>
+#include <sys/xcall.h>
 #include <uvm/uvm_percpu.h>
 
 #ifdef _KERNEL
@@ -215,6 +216,7 @@ struct cpu_info {
 
 #ifdef MULTIPROCESSOR
 	struct srp_hazard	ci_srp_hazards[SRP_HAZARD_NUM];
+	struct xcall_cpu	ci_xcall;
 #define __HAVE_UVM_PERCPU
 	struct uvm_pmr_cache	ci_uvm;		/* [o] page cache */
 #endif
Index: arch/amd64/include/intr.h
===================================================================
RCS file: /cvs/src/sys/arch/amd64/include/intr.h,v
diff -u -p -r1.36 intr.h
--- arch/amd64/include/intr.h	11 Jun 2025 09:57:01 -0000	1.36
+++ arch/amd64/include/intr.h	14 Jul 2025 05:07:42 -0000
@@ -222,7 +222,9 @@ void x86_ipi_handler(void);
 void x86_setperf_ipi(struct cpu_info *);
 
 extern void (*ipifunc[X86_NIPI])(struct cpu_info *);
-#endif
+
+#define cpu_xcall_ipi(_ci) x86_send_ipi((_ci), X86_IPI_XCALL)
+#endif /* MULTIPROCESSOR */
 
 #endif /* !_LOCORE */
 
Index: arch/amd64/include/intrdefs.h
===================================================================
RCS file: /cvs/src/sys/arch/amd64/include/intrdefs.h,v
diff -u -p -r1.24 intrdefs.h
--- arch/amd64/include/intrdefs.h	26 May 2024 13:37:31 -0000	1.24
+++ arch/amd64/include/intrdefs.h	14 Jul 2025 05:07:42 -0000
@@ -85,8 +85,9 @@
 #define X86_IPI_START_VMM		0x00000100
 #define X86_IPI_STOP_VMM		0x00000200
 #define X86_IPI_WBINVD			0x00000400
+#define X86_IPI_XCALL			0x00000800
 
-#define X86_NIPI			12
+#define X86_NIPI			13
 
 #define IREENT_MAGIC	0x18041969
 
Index: conf/files
===================================================================
RCS file: /cvs/src/sys/conf/files,v
diff -u -p -r1.746 files
--- conf/files	13 Jul 2025 05:45:21 -0000	1.746
+++ conf/files	14 Jul 2025 05:07:42 -0000
@@ -751,7 +751,7 @@ file kern/kern_uuid.c
 file kern/kern_watchdog.c		!small_kernel
 file kern/kern_task.c
 file kern/kern_srp.c
-file kern/kern_xcall.c			xcall			needs-flag
+file kern/kern_xcall.c			xcall
 file kern/kern_xxx.c
 file kern/sched_bsd.c
 file kern/subr_autoconf.c