... > > > > - csr_write(CSR_HCOUNTEREN, -1UL); > > > > + /* VS should access only TM bit. Everything else should trap */ > > > > + csr_write(CSR_HCOUNTEREN, 0x02); > > > > > > This looks like something that should be broken out into a separate patch > > > with a description of what happens now when guests try to access the newly > > > trapping counter registers. We should probably also create a TM define. > > > > > > > Done. > > > > As we allow cycles & instret for host user space now [1], should we do the same > for guests as well ? I would prefer not to but same user space > software will start to break > they will run inside a guest. > > https://lore.kernel.org/all/20220928131807.30386-1-palmer@xxxxxxxxxxxx/ > Yeah, it seems like we should either forbid access to unprivileged users or ensure the numbers include some random noise. For guests, a privileged KVM userspace should need to explicitly request access for them, ensuring that the creation of privileged guests is done by conscious choice. Thanks, drew
