According to the mailing list discussion [1] about the preferred approach for notifying hypervisor/VMM about guest entering s2idle state this RFC was implemented. Instead of original hypercall based approach, which involves KVM change [2] and makes it hypervisor specific, implement different mechanism, which takes advantage of MMIO/PIO trapping and makes it hypervisor independent. For the RFCv1 [3]: Patch #1 extends S2Idle ops by new notify handler which will be invoked as a very last command before system actually enters S2Idle states. It also allows to register and use driver specific notification hook which is used in patch #2. Patch #2 introduces new driver for virtual PMC, which registers acpi_s2idle_dev_ops's notify handler. Its implementation is based on an ACPI _DSM evaluation, which in turn can perform MMIO access and allow to trap and therefore notify the VMM about guest entering S2Idle state. For the RFCv2 [4]: the patch #1 was dropped as in the meantime Mario Limonciello introduced a very similar patch [5] which uses s/notify/check and invokes the callback a bit earlier just before s2idle_entry. Mentioned patch has already been merged. This patchset is marked as RFC since patch #2 implements driver for non existing device "HYPE0001", which ACPI ID was not registered yet. Furthermore the required registration process [6] will not be started before getting positive feedback about this patchset. [1] https://patchwork.kernel.org/project/linux-pm/patch/20220609110337.1238762-2-jaz@xxxxxxxxxxxx/ [2] https://patchwork.kernel.org/project/linux-pm/patch/20220609110337.1238762-3-jaz@xxxxxxxxxxxx/ [3] https://patchwork.kernel.org/project/linux-pm/cover/20220707125329.378277-1-jaz@xxxxxxxxxxxx/ [4] https://patchwork.kernel.org/project/linux-pm/cover/20230209152123.3186930-1-jaz@xxxxxxxxxxxx/ [5] https://patchwork.kernel.org/project/linux-pm/patch/20220829162953.5947-2-mario.limonciello@xxxxxxx [6] https://uefi.org/PNP_ACPI_Registry Grzegorz Jaszczyk (1): platform/x86: Add virtual PMC driver used for S2Idle drivers/platform/x86/Kconfig | 7 +++ drivers/platform/x86/Makefile | 3 ++ drivers/platform/x86/virt_pmc.c | 83 +++++++++++++++++++++++++++++++++ 3 files changed, 93 insertions(+) create mode 100644 drivers/platform/x86/virt_pmc.c -- 2.39.1.581.gbfd45094c4-goog
