Fix the hardware watchpoints on SMP amd64. Load the updated %dr

registers also on other CPUs, besides the CPU which happens to execute
the ddb.  The debugging registers are stored in the pcpu area,
together with the command which is executed by the IPI stop handler
upon resume.

Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

4 files changed, 69 insertions, 23 deletions

diff --git a/sys/amd64/amd64/db_trace.c b/sys/amd64/amd64/db_trace.c
index 2c81f87..39297d9 100644
--- a/sys/amd64/amd64/db_trace.c
+++ b/sys/amd64/amd64/db_trace.c
@@ -33,6 +33,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/kdb.h>
 #include <sys/proc.h>
+#include <sys/smp.h>
 #include <sys/stack.h>
 #include <sys/sysent.h>
 
@@ -63,6 +64,8 @@ static db_varfcn_t db_frame;
 static db_varfcn_t db_rsp;
 static db_varfcn_t db_ss;
 
+CTASSERT(sizeof(struct dbreg) == sizeof(((struct pcpu *)NULL)->pc_dbreg));
+
 /*
  * Machine register set.
  */
@@ -591,64 +594,82 @@ db_md_set_watchpoint(addr, size)
 	db_expr_t addr;
 	db_expr_t size;
 {
-	struct dbreg d;
-	int avail, i, wsize;
+	struct dbreg *d;
+	struct pcpu *pc;
+	int avail, c, cpu, i, wsize;
 
-	fill_dbregs(NULL, &d);
+	d = (struct dbreg *)PCPU_PTR(dbreg);
+	cpu = PCPU_GET(cpuid);
+	fill_dbregs(NULL, d);
 
 	avail = 0;
-	for(i = 0; i < 4; i++) {
-		if (!DBREG_DR7_ENABLED(d.dr[7], i))
+	for (i = 0; i < 4; i++) {
+		if (!DBREG_DR7_ENABLED(d->dr[7], i))
 			avail++;
 	}
 
 	if (avail * 8 < size)
 		return (-1);
 
-	for (i = 0; i < 4 && (size > 0); i++) {
-		if (!DBREG_DR7_ENABLED(d.dr[7], i)) {
+	for (i = 0; i < 4 && size > 0; i++) {
+		if (!DBREG_DR7_ENABLED(d->dr[7], i)) {
 			if (size >= 8 || (avail == 1 && size > 4))
 				wsize = 8;
 			else if (size > 2)
 				wsize = 4;
 			else
 				wsize = size;
-			amd64_set_watch(i, addr, wsize,
-				       DBREG_DR7_WRONLY, &d);
+			amd64_set_watch(i, addr, wsize, DBREG_DR7_WRONLY, d);
 			addr += wsize;
 			size -= wsize;
 			avail--;
 		}
 	}
 
-	set_dbregs(NULL, &d);
+	set_dbregs(NULL, d);
+	CPU_FOREACH(c) {
+		if (c == cpu)
+			continue;
+		pc = pcpu_find(c);
+		memcpy(pc->pc_dbreg, d, sizeof(*d));
+		pc->pc_dbreg_cmd = PC_DBREG_CMD_LOAD;
+	}
 
-	return(0);
+	return (0);
 }
 
-
 int
 db_md_clr_watchpoint(addr, size)
 	db_expr_t addr;
 	db_expr_t size;
 {
-	struct dbreg d;
-	int i;
+	struct dbreg *d;
+	struct pcpu *pc;
+	int i, c, cpu;
 
-	fill_dbregs(NULL, &d);
+	d = (struct dbreg *)PCPU_PTR(dbreg);
+	cpu = PCPU_GET(cpuid);
+	fill_dbregs(NULL, d);
 
-	for(i = 0; i < 4; i++) {
-		if (DBREG_DR7_ENABLED(d.dr[7], i)) {
-			if ((DBREG_DRX((&d), i) >= addr) &&
-			    (DBREG_DRX((&d), i) < addr+size))
-				amd64_clr_watch(i, &d);
+	for (i = 0; i < 4; i++) {
+		if (DBREG_DR7_ENABLED(d->dr[7], i)) {
+			if (DBREG_DRX((d), i) >= addr &&
+			    DBREG_DRX((d), i) < addr + size)
+				amd64_clr_watch(i, d);
 
 		}
 	}
 
-	set_dbregs(NULL, &d);
+	set_dbregs(NULL, d);
+	CPU_FOREACH(c) {
+		if (c == cpu)
+			continue;
+		pc = pcpu_find(c);
+		memcpy(pc->pc_dbreg, d, sizeof(*d));
+		pc->pc_dbreg_cmd = PC_DBREG_CMD_LOAD;
+	}
 
-	return(0);
+	return (0);
 }
 
 
@@ -699,3 +720,17 @@ db_md_list_watchpoints()
 	}
 	db_printf("\n");
 }
+
+void
+amd64_db_resume_dbreg(void)
+{
+	struct dbreg *d;
+
+	switch (PCPU_GET(dbreg_cmd)) {
+	case PC_DBREG_CMD_LOAD:
+		d = (struct dbreg *)PCPU_PTR(dbreg);
+		set_dbregs(NULL, d);
+		PCPU_SET(dbreg_cmd, PC_DBREG_CMD_NONE);
+		break;
+	}
+}
diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
index 31dbb3f..5f4aacf 100644
--- a/sys/amd64/amd64/mp_machdep.c
+++ b/sys/amd64/amd64/mp_machdep.c
@@ -28,6 +28,7 @@
 __FBSDID("$FreeBSD$");
 
 #include "opt_cpu.h"
+#include "opt_ddb.h"
 #include "opt_kstack_pages.h"
 #include "opt_sched.h"
 #include "opt_smp.h"
@@ -1396,6 +1397,10 @@ cpustop_handler(void)
 	CPU_CLR_ATOMIC(cpu, &started_cpus);
 	CPU_CLR_ATOMIC(cpu, &stopped_cpus);
 
+#ifdef DDB
+	amd64_db_resume_dbreg();
+#endif
+
 	if (cpu == 0 && cpustop_restartfunc != NULL) {
 		cpustop_restartfunc();
 		cpustop_restartfunc = NULL;
diff --git a/sys/amd64/include/md_var.h b/sys/amd64/include/md_var.h
index 5d7cb74..6ffcf63 100644
--- a/sys/amd64/include/md_var.h
+++ b/sys/amd64/include/md_var.h
@@ -117,5 +117,6 @@ void	minidumpsys(struct dumperinfo *);
 struct savefpu *get_pcb_user_save_td(struct thread *td);
 struct savefpu *get_pcb_user_save_pcb(struct pcb *pcb);
 struct pcb *get_pcb_td(struct thread *td);
+void	amd64_db_resume_dbreg(void);
 
 #endif /* !_MACHINE_MD_VAR_H_ */
diff --git a/sys/amd64/include/pcpu.h b/sys/amd64/include/pcpu.h
index bb7d339..ba4c618 100644
--- a/sys/amd64/include/pcpu.h
+++ b/sys/amd64/include/pcpu.h
@@ -78,9 +78,14 @@
 	struct system_segment_descriptor *pc_tss;			\
 	u_int	pc_cmci_mask		/* MCx banks for CMCI */	\
 	PCPU_XEN_FIELDS;						\
-	char	__pad[293]		/* be divisor of PAGE_SIZE	\
+	uint64_t pc_dbreg[16];		/* ddb debugging regs */	\
+	int pc_dbreg_cmd;		/* ddb debugging reg cmd */	\
+	char	__pad[161]		/* be divisor of PAGE_SIZE	\
 					   after cache alignment */
 
+#define	PC_DBREG_CMD_NONE	0
+#define	PC_DBREG_CMD_LOAD	1
+
 #ifdef _KERNEL
 
 #ifdef lint