On Wed, Nov 02, 2022 at 04:33:15PM +0000, Sean Christopherson wrote:
> 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: {
Ah, makes sense, thanks!
--
Peter Xu
