On Thu, Aug 09, 2018 at 12:13:24PM +0200, Igor Mammedov wrote: > On Wed, 8 Aug 2018 23:20:25 +0300 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > On Wed, Aug 08, 2018 at 05:15:45PM +0200, Igor Mammedov wrote: > > > It's an alternative approach to > > > 1) [PATCH hack dontapply v2 0/7] Dynamic _CST generation > > > which instead of dynamic AML loading uses static AML with > > > dynamic values. It allows us to keep firmware blob static and > > > to avoid split firmware issue (1) in case of cross version migration. > > > > I think there's a misunderstanding. That patch only declares a couple of > > states but that is just for debugging/demonstration purposes. A typical > > real CPU has more states (e.g. some intel CPUs have ~10 levels). > yep, baremetal has more CStates, but that depends on what we are trying to > achieve here. > If goal is to use mwait/monitor instead o halt when idle > to reduce wakeup latencies then 1 entry in _CST is sufficient.
1 entry is not sufficient in my testing. My testing shows we want to stay in guest for states with latency up to ~200 usec to get measureable latency gains. > If target is reduce power consumption than we would need more entries. > In the later case _CST is probably not sufficient as it provides only > power/latency pair while intel_idle also provides target residence. > So if power mgmt target is considered, we need to use new _LPI > which means guest will need support for it as well, not sure if x86 > kernel supports it nor aware of such support in Windows (hopefully it > would just ignore unknown method) I think we want to address both goals. Linux on x86 does support _LPI and I agree it's a good idea to be able to pass that in. Will take a look. But intel_idle seems to just set target = latency * 2 so I am not sure it's all that important. > > > > > ABI in this case is confined to cpu hotplug IO registers > > > (i.e. do it old school way, like we used to do so far). > > > This way we don't have to add yet another ABI to keep dynamic > > > AML code under control (1). > > > > > > Tested with: XPsp3 - ws2106 guests. > > > > > > CC: "Michael S. Tsirkin" <m...@redhat.com> > > > > > > > > > Igor Mammedov (3): > > > acpi: add aml_create_byte_field() > > > pc: acpi: add _CST support > > > acpi: add support for CST update notification > > > > > > Michael S. Tsirkin (1): > > > acpi: aml: add aml_register() > > > > > > include/hw/acpi/aml-build.h | 6 ++ > > > include/hw/acpi/cpu.h | 10 +++ > > > docs/specs/acpi_cpu_hotplug.txt | 21 +++++- > > > hw/acpi/aml-build.c | 28 +++++++ > > > hw/acpi/cpu.c | 158 > > > +++++++++++++++++++++++++++++++++++++++- > > > hw/acpi/piix4.c | 2 + > > > hw/i386/acpi-build.c | 5 +- > > > tests/bios-tables-test.c | 1 + > > > 8 files changed, 225 insertions(+), 6 deletions(-) > > > > > > -- > > > 2.7.4
