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From:
hshoexer <hshoexer@yerbouti.franken.de>
Subject:
rewrite wbinvd_on_all_cpus_acked() using cpu_xcall(9)
To:
tech@openbsd.org
Date:
Thu, 6 Nov 2025 15:38:55 +0100

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Hi,

I'd like to simplify the implementation of amd64's
wbinvd_on_all_cpus_acked() by using cpu_xcall(9).

The diff below rewrites wbinvd_on_all_cpus_acked() accordingly.

The required xcall glue code for amd64 is from this [1] mail by
dlg@.  If the wbinvd_on_all_cpus_acked() is ok, I'm fine with
splitting this diff.

Thoughts?

Take care,
HJ.

[1] https://marc.info/?l=openbsd-tech&m=175246988124240
-----------------------------------------------------------------
commit 394bdebb36b1c9699343896fa2091cd1f52be6e3
Author: hshoexer <hshoexer@yerbouti.franken.de>
Date:   Thu Nov 6 15:01:52 2025 +0100

    rewrite wbinvd_on_all_cpus_acked() using cpu_xcall(9)
    
    change includes required amd64 glue code by dlg@ as seen here:
    https://marc.info/?l=openbsd-tech&m=175246988124240

diff --git a/sys/arch/amd64/amd64/cpu.c b/sys/arch/amd64/amd64/cpu.c
index 5baf179a398..93f554cb652 100644
--- a/sys/arch/amd64/amd64/cpu.c
+++ b/sys/arch/amd64/amd64/cpu.c
@@ -79,6 +79,7 @@
 #include <sys/memrange.h>
 #include <sys/atomic.h>
 #include <sys/user.h>
+#include <sys/xcall.h>
 
 #include <uvm/uvm_extern.h>
 
@@ -642,6 +643,8 @@ cpu_attach(struct device *parent, struct device *self, void *aux)
 #endif
 
 #if defined(MULTIPROCESSOR)
+	cpu_xcall_establish(ci);
+
 	/*
 	 * Allocate UPAGES contiguous pages for the idle PCB and stack.
 	 */
@@ -1475,44 +1478,23 @@ wbinvd_on_all_cpus(void)
 	return 0;
 }
 
-volatile long wbinvd_wait __attribute__((section(".kudata")));
+static void
+xcwbinvd(void *arg)
+{
+	wbinvd();
+}
 
 void
 wbinvd_on_all_cpus_acked(void)
 {
-	struct cpu_info *ci, *self = curcpu();;
-	CPU_INFO_ITERATOR cii;
-	long wait = 0;
-	u_int64_t mask = 0;
-	int s;
+	struct cpu_info		*ci;
+	CPU_INFO_ITERATOR	 cii;
 
 	CPU_INFO_FOREACH(cii, ci) {
-		if (ci == self || !(ci->ci_flags & CPUF_RUNNING))
+		if (!(ci->ci_flags & CPUF_RUNNING))
 			continue;
-		mask |= (1ULL << ci->ci_cpuid);
-		wait++;
-	}
-
-	if (wait > 0) {
-		s = splvm();
-		while (atomic_cas_ulong(&wbinvd_wait, 0 , wait) != 0) {
-			while (wbinvd_wait != 0)
-				CPU_BUSY_CYCLE();
-		}
-
-		CPU_INFO_FOREACH(cii, ci) {
-			if ((mask & (1ULL << ci->ci_cpuid)) == 0)
-				continue;
-			if (x86_fast_ipi(ci, LAPIC_IPI_WBINVD) != 0)
-				panic("%s: ipi failed", __func__);
-		}
-		splx(s);
+		cpu_xcall_sync(ci, xcwbinvd, NULL, "xcwbinvd");
 	}
-
-	wbinvd();
-
-	while (wbinvd_wait != 0)
-		CPU_BUSY_CYCLE();
 }
 #endif /* MULTIPROCESSOR */
 
diff --git a/sys/arch/amd64/amd64/ipifuncs.c b/sys/arch/amd64/amd64/ipifuncs.c
index 482fc9eebb4..8a068278fc2 100644
--- a/sys/arch/amd64/amd64/ipifuncs.c
+++ b/sys/arch/amd64/amd64/ipifuncs.c
@@ -108,6 +108,7 @@ void (*ipifunc[X86_NIPI])(struct cpu_info *) =
 	NULL,
 #endif
 	x86_64_ipi_wbinvd,
+	cpu_xcall_dispatch,
 };
 
 void
diff --git a/sys/arch/amd64/amd64/lapic.c b/sys/arch/amd64/amd64/lapic.c
index f7fdb81ccca..ccf743303f2 100644
--- a/sys/arch/amd64/amd64/lapic.c
+++ b/sys/arch/amd64/amd64/lapic.c
@@ -364,8 +364,6 @@ lapic_boot_init(paddr_t lapic_base)
 		idt_vec_set(LAPIC_IPI_INVLPG, Xipi_invlpg_pcid);
 		idt_vec_set(LAPIC_IPI_INVLRANGE, Xipi_invlrange_pcid);
 	}
-	idt_allocmap[LAPIC_IPI_WBINVD] = 1;
-	idt_vec_set(LAPIC_IPI_WBINVD, Xipi_wbinvd);
 #if NVMM > 0
 	idt_allocmap[LAPIC_IPI_INVEPT] = 1;
 	idt_vec_set(LAPIC_IPI_INVEPT, Xipi_invept);
diff --git a/sys/arch/amd64/amd64/vector.S b/sys/arch/amd64/amd64/vector.S
index 8b82db6b4f6..c531c9f827c 100644
--- a/sys/arch/amd64/amd64/vector.S
+++ b/sys/arch/amd64/amd64/vector.S
@@ -816,17 +816,6 @@ IDTVEC(ipi_invlrange_pcid)
 	iretq
 END(Xipi_invlrange_pcid)
 
-IDTVEC(ipi_wbinvd)
-	ioapic_asm_ack()
-
-	wbinvd
-
-	lock
-	decq	wbinvd_wait
-
-	iretq
-END(Xipi_wbinvd)
-
 #endif /* MULTIPROCESSOR */
 
 	/*
diff --git a/sys/arch/amd64/conf/files.amd64 b/sys/arch/amd64/conf/files.amd64
index 630de36a01d..38d5796f650 100644
--- a/sys/arch/amd64/conf/files.amd64
+++ b/sys/arch/amd64/conf/files.amd64
@@ -95,7 +95,7 @@ file	arch/amd64/amd64/mpbios.c		mpbios needs-flag
 file	arch/amd64/amd64/mpbios_intr_fixup.c	mpbios & pci
 
 define	cpu {[apid = -1]}
-device	cpu
+device	cpu: xcall
 attach	cpu at mainbus
 file	arch/amd64/amd64/cpu.c	cpu
 
diff --git a/sys/arch/amd64/include/cpu.h b/sys/arch/amd64/include/cpu.h
index b125f1c4d50..f3b8ec80d96 100644
--- a/sys/arch/amd64/include/cpu.h
+++ b/sys/arch/amd64/include/cpu.h
@@ -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
diff --git a/sys/arch/amd64/include/i82489var.h b/sys/arch/amd64/include/i82489var.h
index 561efa3fbd7..95dfff5173d 100644
--- a/sys/arch/amd64/include/i82489var.h
+++ b/sys/arch/amd64/include/i82489var.h
@@ -72,8 +72,7 @@ extern void Xresume_lapic_ipi(void);
 #define LAPIC_IPI_INVLTLB			(LAPIC_IPI_OFFSET + 0)
 #define LAPIC_IPI_INVLPG			(LAPIC_IPI_OFFSET + 1)
 #define LAPIC_IPI_INVLRANGE			(LAPIC_IPI_OFFSET + 2)
-#define LAPIC_IPI_WBINVD			(LAPIC_IPI_OFFSET + 3)
-#define LAPIC_IPI_INVEPT			(LAPIC_IPI_OFFSET + 4)
+#define LAPIC_IPI_INVEPT			(LAPIC_IPI_OFFSET + 3)
 
 extern void Xipi_invltlb(void);
 extern void Xipi_invltlb_pcid(void);
@@ -81,7 +80,6 @@ extern void Xipi_invlpg(void);
 extern void Xipi_invlpg_pcid(void);
 extern void Xipi_invlrange(void);
 extern void Xipi_invlrange_pcid(void);
-extern void Xipi_wbinvd(void);
 #if NVMM > 0
 extern void Xipi_invept(void);
 #endif /* NVMM > 0 */
diff --git a/sys/arch/amd64/include/intr.h b/sys/arch/amd64/include/intr.h
index c0e12824c2d..ffdff36ca38 100644
--- a/sys/arch/amd64/include/intr.h
+++ b/sys/arch/amd64/include/intr.h
@@ -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 */
 
diff --git a/sys/arch/amd64/include/intrdefs.h b/sys/arch/amd64/include/intrdefs.h
index 048d0202b88..69238b46155 100644
--- a/sys/arch/amd64/include/intrdefs.h
+++ b/sys/arch/amd64/include/intrdefs.h
@@ -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
 
diff --git a/sys/conf/files b/sys/conf/files
index 59df8c6fd1b..1e00c25cb6c 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -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