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

Sean Christopherson
2020-09-23T22:45:36Z

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@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Cc: linux-mips@vger.kernel.org
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: kvm-ppc@vger.kernel.org
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
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