On Wed, Nov 02, 2022, Peter Xu wrote:
> Might be slightly off-topic: I didn't quickly spot how do we guarantee two
> threads doing KVM_RUN ioctl on the same vcpu fd concurrently. I know
> that's insane and could have corrupted things, but I just want to make sure
> e.g. even a malicious guest app won't be able to trigger host warnings.
kvm_vcpu_ioctl() takes the vCPU's mutex:
static long kvm_vcpu_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
...
/*
* Some architectures have vcpu ioctls that are asynchronous to vcpu
* execution; mutex_lock() would break them.
*/
r = kvm_arch_vcpu_async_ioctl(filp, ioctl, arg);
if (r != -ENOIOCTLCMD)
return r;
if (mutex_lock_killable(&vcpu->mutex))
return -EINTR;
switch (ioctl) {
case KVM_RUN: {
