On Tue, Nov 20, 2018 at 10:31:36PM +1100, Michael Ellerman wrote:

Andrew Murray [off-list ref] writes:

quoted

Update design.txt to reflect the presence of the exclude_host
and exclude_guest perf flags.

Signed-off-by: Andrew Murray <redacted>
---
 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