On Tue, Nov 20, 2018 at 10:31:36PM +1100, Michael Ellerman wrote: > Andrew Murray <andrew.murray@xxxxxxx> writes: > > > Update design.txt to reflect the presence of the exclude_host > > and exclude_guest perf flags. > > > > Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx> > > --- > > tools/perf/design.txt | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/tools/perf/design.txt b/tools/perf/design.txt > > index a28dca2..7de7d83 100644 > > --- a/tools/perf/design.txt > > +++ b/tools/perf/design.txt > > @@ -222,6 +222,10 @@ The 'exclude_user', 'exclude_kernel' and 'exclude_hv' bits provide a > > way to request that counting of events be restricted to times when the > > CPU is in user, kernel and/or hypervisor mode. > > > > +Furthermore the 'exclude_host' and 'exclude_guest' bits provide a way > > +to request counting of events restricted to guest and host contexts when > > +using virtualisation. > > How does exclude_host differ from exclude_hv ? I believe exclude_host / exclude_guest are intented to distinguish between host and guest in the hosted hypervisor context (KVM). Whereas exclude_hv allows to distinguish between guest and hypervisor in the bare-metal type hypervisors. In the case of arm64 - if VHE extensions are present then the host kernel will run at a higher privilege to the guest kernel, in which case there is no distinction between hypervisor and host so we ignore exclude_hv. But where VHE extensions are not present then the host kernel runs at the same privilege level as the guest and we use a higher privilege level to switch between them - in this case we can use exclude_hv to discount that hypervisor role of switching between guests. Thanks, Andrew Murray > > cheers
