qemu-targetstep: Attempt to track guest process gfn when running in userspace

Seems like single-stepping the guest with LAPIC influences the guest scheduler behaviour, since just a single step inside the target gfn (to determine if its running in userspace), is enough to for us to never reach the GUEST_STOP_TRACK event. FWICT the single-stepping is not frequent and does not take long enough to justify never reaching the stop event.

1 files changed, 50 insertions, 0 deletions

diff --git a/test/qemu-targetstep_guest.c b/test/qemu-targetstep_guest.c
new file mode 100644
index 0000000..9ef36e1
--- /dev/null
+++ b/test/qemu-targetstep_guest.c
@@ -0,0 +1,50 @@
+#include "cachepc/uapi.h"
+
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <errno.h>
+#include <err.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+main(int argc, const char **argv)
+{
+	void *buf;
+	int ret;
+
+	buf = NULL;
+	if (posix_memalign(&buf, L1_LINESIZE * L1_SETS, L1_LINESIZE * L1_SETS))
+		err(1, "memalign");
+	memset(buf, 0, L1_LINESIZE * L1_SETS);
+
+	errno = 0;
+	ret = setpriority(PRIO_PROCESS, 0, -20);
+	if (errno) err(1, "setpriority");
+	printf("NICE %i\n", ret);
+
+	while (1) {
+		printf("LOOP\n");
+		CPC_DO_VMMCALL(KVM_HC_CPC_VMMCALL_SIGNAL,
+			CPC_GUEST_START_TRACK, 0);
+		*(uint8_t *)(buf + L1_LINESIZE * 9) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 10) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 11) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 12) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 13) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 14) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 15) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 9) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 10) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 11) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 12) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 13) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 14) = 1;
+		*(uint8_t *)(buf + L1_LINESIZE * 15) = 1;
+		CPC_DO_VMMCALL(KVM_HC_CPC_VMMCALL_SIGNAL,
+			CPC_GUEST_STOP_TRACK, 0);
+	}
+}