Hi Sai, On Fri, Oct 16, 2020 at 02:10:47PM +0530, Sai Prakash Ranjan wrote: > Hi Leo, > > On 2020-10-16 12:54, Leo Yan wrote: > > On Thu, Oct 15, 2020 at 11:40:05PM -0700, Denis Nikitin wrote: > > > Hi Mathieu, > > > > > > I think one of the use cases could be VMs. > > > Is there isolation between EL1 guest kernels which we can control > > > from perf > > > in a system wide mode? > > > > Sorry for suddenly jumping in. > > > > For KVM, I think we need to implement mechanism for saving/restoring > > CoreSight context for every guest OS, the CPU PMUs has implemented > > related features [1]. > > > > Thanks, > > Leo > > > > [1] > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kvm/pmu.c > > > > What happens to the sysfs mode of tracing? For that we would still > need a config right to exclude kernel mode tracing completely. IIUC, sysfs mode and perf mode both can apply the same approach, the guest OS runs a thread context for the host, so when a guest OS is switched in or out, the hypervisor can save/restore the context for the guest OS; thus every guest OS will have its dedicated context and trace data ideally. Thanks, Leo
