On 2020/10/23 17:59, Lorenzo Pieralisi wrote:
On Thu, Oct 22, 2020 at 01:45:32PM +0800, Hanjun Guo wrote:
Hi Lorenzo,
On 2020/10/22 1:26, Lorenzo Pieralisi via Linaro-open-discussions wrote:
Hi all,
according to the topics posted previously on the list, I suggest we tackle the following ones on Nov 4th (all topics posted are interesting but some require some time to elaborate following KVM forum next week):
- Hanjun/Shameer - IORT reserved memory support
- Zhangfei/Wangzhou - SVA support for SMMU stall mode
- Hanjun - Uncore DVFS and how to support it (needs spec update, either ARM specs or ACPI)
Hi Hanjun,
Hi Lorenzo,
in preparation for the discussion, may I ask you please to elaborate a bit more on the Uncore DVFS topic so that we have more background info ?
Sure, for the later generation of Kunpeng server chip, there is a Uncore block in the chip which contains L3 cache, ring buses and etc., the Uncore stays in a single power domain and can do DVFS at runtime. As the Uncore consumes considerable power, so it's better to control the frequency at runtime.
The Uncore can be abstracted as a power device, and the power can be controlled via a single interface such as MMIO, but the permission is only restricted in EL3 (avoid spectre via DVFS), so I think we need a spec update to control the power for Uncore devices, like PSCI or SCMI, or an common interface for ACPI spec.
Please let me know if I didn't explain it in detail, I can prepare a slide for the meeting if needed.
Thanks Hanjun