From fc276d92ae91bc7d48bda15996c70837c88f7d99 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 6 Apr 2018 22:03:43 +0000
Subject: Add a way to temporarily suspend and resume virtual CPUs.

This is used as part of implementing run control in bhyve's debug
server.  The hypervisor now maintains a set of "debugged" CPUs.
Attempting to run a debugged CPU will fail to execute any guest
instructions and will instead report a VM_EXITCODE_DEBUG exit to
the userland hypervisor.  Virtual CPUs are placed into the debugged
state via vm_suspend_cpu() (implemented via a new VM_SUSPEND_CPU ioctl).
Virtual CPUs can be resumed via vm_resume_cpu() (VM_RESUME_CPU ioctl).

The debug server suspends virtual CPUs when it wishes them to stop
executing in the guest (for example, when a debugger attaches to the
server).  The debug server can choose to resume only a subset of CPUs
(for example, when single stepping) or it can choose to resume all
CPUs.  The debug server must explicitly mark a CPU as resumed via
vm_resume_cpu() before the virtual CPU will successfully execute any
guest instructions.

Reviewed by:	avg, grehan
Tested on:	Intel (jhb), AMD (avg)
Differential Revision:	https://reviews.freebsd.org/D14466
---
 lib/libvmmapi/vmmapi.c | 34 +++++++++++++++++++++++++++++++++-
 lib/libvmmapi/vmmapi.h |  3 +++
 2 files changed, 36 insertions(+), 1 deletion(-)

(limited to 'lib/libvmmapi')

diff --git a/lib/libvmmapi/vmmapi.c b/lib/libvmmapi/vmmapi.c
index 292e749eaaa2..ecb21f0dcdc1 100644
--- a/lib/libvmmapi/vmmapi.c
+++ b/lib/libvmmapi/vmmapi.c
@@ -1373,6 +1373,13 @@ vm_suspended_cpus(struct vmctx *ctx, cpuset_t *cpus)
 	return (vm_get_cpus(ctx, VM_SUSPENDED_CPUS, cpus));
 }
 
+int
+vm_debug_cpus(struct vmctx *ctx, cpuset_t *cpus)
+{
+
+	return (vm_get_cpus(ctx, VM_DEBUG_CPUS, cpus));
+}
+
 int
 vm_activate_cpu(struct vmctx *ctx, int vcpu)
 {
@@ -1385,6 +1392,30 @@ vm_activate_cpu(struct vmctx *ctx, int vcpu)
 	return (error);
 }
 
+int
+vm_suspend_cpu(struct vmctx *ctx, int vcpu)
+{
+	struct vm_activate_cpu ac;
+	int error;
+
+	bzero(&ac, sizeof(struct vm_activate_cpu));
+	ac.vcpuid = vcpu;
+	error = ioctl(ctx->fd, VM_SUSPEND_CPU, &ac);
+	return (error);
+}
+
+int
+vm_resume_cpu(struct vmctx *ctx, int vcpu)
+{
+	struct vm_activate_cpu ac;
+	int error;
+
+	bzero(&ac, sizeof(struct vm_activate_cpu));
+	ac.vcpuid = vcpu;
+	error = ioctl(ctx->fd, VM_RESUME_CPU, &ac);
+	return (error);
+}
+
 int
 vm_get_intinfo(struct vmctx *ctx, int vcpu, uint64_t *info1, uint64_t *info2)
 {
@@ -1501,7 +1532,8 @@ vm_get_ioctls(size_t *len)
 	    VM_SET_X2APIC_STATE, VM_GET_X2APIC_STATE,
 	    VM_GET_HPET_CAPABILITIES, VM_GET_GPA_PMAP, VM_GLA2GPA,
 	    VM_GLA2GPA_NOFAULT,
-	    VM_ACTIVATE_CPU, VM_GET_CPUS, VM_SET_INTINFO, VM_GET_INTINFO,
+	    VM_ACTIVATE_CPU, VM_GET_CPUS, VM_SUSPEND_CPU, VM_RESUME_CPU,
+	    VM_SET_INTINFO, VM_GET_INTINFO,
 	    VM_RTC_WRITE, VM_RTC_READ, VM_RTC_SETTIME, VM_RTC_GETTIME,
 	    VM_RESTART_INSTRUCTION };
 
diff --git a/lib/libvmmapi/vmmapi.h b/lib/libvmmapi/vmmapi.h
index e391d9131e86..da7267cba59d 100644
--- a/lib/libvmmapi/vmmapi.h
+++ b/lib/libvmmapi/vmmapi.h
@@ -216,7 +216,10 @@ int	vcpu_reset(struct vmctx *ctx, int vcpu);
 
 int	vm_active_cpus(struct vmctx *ctx, cpuset_t *cpus);
 int	vm_suspended_cpus(struct vmctx *ctx, cpuset_t *cpus);
+int	vm_debug_cpus(struct vmctx *ctx, cpuset_t *cpus);
 int	vm_activate_cpu(struct vmctx *ctx, int vcpu);
+int	vm_suspend_cpu(struct vmctx *ctx, int vcpu);
+int	vm_resume_cpu(struct vmctx *ctx, int vcpu);
 
 /*
  * FreeBSD specific APIs
-- 
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