[RFC PATCH 2/3] KVM: Add infrastructure and macro to mark VM as bugged

[Sean Christopherson <sean.j.christopherson@xxxxxxxxx>]

Introduce the concept of a "bugged VM", i.e. a VM that has encountered a
KVM bug and/or a CPU bug and is, for all intents and purposes, dead in
the water.  Marking a VM as bugged is especially helpful to handle
scenarios that can only be reach if there is a software/hardware bug,
but can't easily return an error, e.g. x86's register caching callbacks.

Reject all ioctls() if a VM is bugged, and provide a new request so that
arch specific code can kick running vCPUs out to userspace.

Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Julien Thierry <julien.thierry.kdev@xxxxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: Huacai Chen <chenhc@xxxxxxxxxx>
Cc: Aleksandar Markovic <aleksandar.qemu.devel@xxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxxx
Cc: Paul Mackerras <paulus@xxxxxxxxxx>
Cc: kvm-ppc@xxxxxxxxxxxxxxx
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Janosch Frank <frankja@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Cornelia Huck <cohuck@xxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Cc: Jim Mattson <jmattson@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 include/linux/kvm_host.h | 27 +++++++++++++++++++++++++++
 virt/kvm/kvm_main.c      | 10 +++++-----
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1d70aeeb7ec3..cb527d55908d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -146,6 +146,7 @@ static inline bool is_error_page(struct page *page)
 #define KVM_REQ_MMU_RELOAD        (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_PENDING_TIMER     2
 #define KVM_REQ_UNHALT            3
+#define KVM_REQ_VM_BUGGED	  (4 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQUEST_ARCH_BASE     8
 
 #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \
@@ -513,6 +514,8 @@ struct kvm {
 	struct srcu_struct irq_srcu;
 	pid_t userspace_pid;
 	unsigned int max_halt_poll_ns;
+
+	bool vm_bugged;
 };
 
 #define kvm_err(fmt, ...) \
@@ -541,6 +544,30 @@ struct kvm {
 #define vcpu_err(vcpu, fmt, ...)					\
 	kvm_err("vcpu%i " fmt, (vcpu)->vcpu_id, ## __VA_ARGS__)
 
+static inline void kvm_vm_bugged(struct kvm *kvm)
+{
+	kvm->vm_bugged = true;
+	kvm_make_all_cpus_request(kvm, KVM_REQ_VM_BUGGED);
+}
+
+#define KVM_BUG(cond, kvm, fmt...)				\
+({								\
+	int __ret = (cond);					\
+								\
+	if (WARN_ONCE(__ret && !(kvm)->vm_bugged, fmt))		\
+		kvm_vm_bugged(kvm);				\
+	unlikely(__ret);					\
+})
+
+#define KVM_BUG_ON(cond, kvm)					\
+({								\
+	int __ret = (cond);					\
+								\
+	if (WARN_ON_ONCE(__ret && !(kvm)->vm_bugged))		\
+		kvm_vm_bugged(kvm);				\
+	unlikely(__ret);					\
+})
+
 static inline bool kvm_dirty_log_manual_protect_and_init_set(struct kvm *kvm)
 {
 	return !!(kvm->manual_dirty_log_protect & KVM_DIRTY_LOG_INITIALLY_SET);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bf3f333c7a19..e216ce9d1c39 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3191,7 +3191,7 @@ static long kvm_vcpu_ioctl(struct file *filp,
 	struct kvm_fpu *fpu = NULL;
 	struct kvm_sregs *kvm_sregs = NULL;
 
-	if (vcpu->kvm->mm != current->mm)
+	if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_bugged)
 		return -EIO;
 
 	if (unlikely(_IOC_TYPE(ioctl) != KVMIO))
@@ -3397,7 +3397,7 @@ static long kvm_vcpu_compat_ioctl(struct file *filp,
 	void __user *argp = compat_ptr(arg);
 	int r;
 
-	if (vcpu->kvm->mm != current->mm)
+	if (vcpu->kvm->mm != current->mm || vcpu->kvm->vm_bugged)
 		return -EIO;
 
 	switch (ioctl) {
@@ -3463,7 +3463,7 @@ static long kvm_device_ioctl(struct file *filp, unsigned int ioctl,
 {
 	struct kvm_device *dev = filp->private_data;
 
-	if (dev->kvm->mm != current->mm)
+	if (dev->kvm->mm != current->mm || dev->kvm->vm_bugged)
 		return -EIO;
 
 	switch (ioctl) {
@@ -3679,7 +3679,7 @@ static long kvm_vm_ioctl(struct file *filp,
 	void __user *argp = (void __user *)arg;
 	int r;
 
-	if (kvm->mm != current->mm)
+	if (kvm->mm != current->mm || kvm->vm_bugged)
 		return -EIO;
 	switch (ioctl) {
 	case KVM_CREATE_VCPU:
@@ -3874,7 +3874,7 @@ static long kvm_vm_compat_ioctl(struct file *filp,
 	struct kvm *kvm = filp->private_data;
 	int r;
 
-	if (kvm->mm != current->mm)
+	if (kvm->mm != current->mm || kvm->vm_bugged)
 		return -EIO;
 	switch (ioctl) {
 	case KVM_GET_DIRTY_LOG: {
-- 
2.28.0