RE: [RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for S2Idle

Limonciello, Mario
2023-02-09T18:25:50Z

[AMD Official Use Only - General]

> -----Original Message-----
> From: Grzegorz Jaszczyk <jaz@semihalf.com>
> Sent: Thursday, February 9, 2023 09:21
> To: linux-kernel@vger.kernel.org; rafael@kernel.org
> Cc: dmy@semihalf.com; tn@semihalf.com; dbehr@google.com;
> zide.chen@intel.corp-partner.google.com; seanjc@google.com;
> upstream@semihalf.com; hdegoede@redhat.com; markgross@kernel.org;
> dtor@google.com; Limonciello, Mario <Mario.Limonciello@amd.com>; linux-
> pm@vger.kernel.org; x86@kernel.org; platform-driver-x86@vger.kernel.org;
> Grzegorz Jaszczyk <jaz@semihalf.com>
> Subject: [RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for
> S2Idle
>
> Virtual PMC driver is meant for the guest VMs for the S2Idle
> notification. Its purpose is to register S2Idle dev ops check handler,
> which will evaluate ACPI _DSM just before the guest enters S2Idle power
> state.
>
> This allows to trap on MMIO access done as a consequence of _DSM
> evaluation and therefore notify the VMM about the guest entering S2Idle
> state.
>
> Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
> ---
> Changelog v1..v2:
> - Take advantage of acpi_s2idle_dev_ops's check() instead of notify()
> ---
> drivers/platform/x86/Kconfig | 7 ++++
> drivers/platform/x86/Makefile | 3 ++
> drivers/platform/x86/virt_pmc.c | 73
> +++++++++++++++++++++++++++++++++
> 3 files changed, 83 insertions(+)
> create mode 100644 drivers/platform/x86/virt_pmc.c
>
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 5692385e2d26..b7c3f98031d7 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1099,6 +1099,13 @@ config WINMATE_FM07_KEYS
> buttons below the display. This module adds an input device
> that delivers key events when these buttons are pressed.
>
> +config VIRT_PMC
> + tristate "Virt PMC"
> + depends on ACPI && SUSPEND
> + help
> + The Virtual PMC driver is meant for the guest VMs and its main
> + purpose is to notify about guest entering s2idle state.
> +
> endif # X86_PLATFORM_DEVICES
>
> config P2SB
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index 1d3d1b02541b..c4d3056cf4ea 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -129,6 +129,9 @@ obj-$(CONFIG_INTEL_SCU_WDT) +=
> intel_scu_wdt.o
> obj-$(CONFIG_INTEL_SCU_IPC_UTIL) += intel_scu_ipcutil.o
> obj-$(CONFIG_X86_INTEL_LPSS) += pmc_atom.o
>
> +# Virtual PMC
> +obj-$(CONFIG_VIRT_PMC) += virt_pmc.o
> +
> # Siemens Simatic Industrial PCs
> obj-$(CONFIG_SIEMENS_SIMATIC_IPC) += simatic-ipc.o
>
> diff --git a/drivers/platform/x86/virt_pmc.c
> b/drivers/platform/x86/virt_pmc.c
> new file mode 100644
> index 000000000000..daf9c9ed86e5
> --- /dev/null
> +++ b/drivers/platform/x86/virt_pmc.c
> @@ -0,0 +1,73 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Virtual Power Management Controller Driver
> + *
> + * Author: Grzegorz Jaszczyk <jaz@semihalf.com>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/platform_device.h>
> +
> +#define ACPI_VIRT_PMC_DSM_UUID "9ea49ba3-434a-49a6-be30-
> 37cc55c4d397"
> +#define ACPI_VIRT_PMC_NOTIFY 1
> +
> +static acpi_handle virt_pmc_handle;
> +
> +static void virt_pmc_s2idle_notify(void)
> +{
> + union acpi_object *out_obj;
> + static guid_t dsm_guid;
> +
> + guid_parse(ACPI_VIRT_PMC_DSM_UUID, &dsm_guid);
> +
> + out_obj = acpi_evaluate_dsm(virt_pmc_handle, &dsm_guid,
> + 0, ACPI_VIRT_PMC_NOTIFY, NULL);
> +
> + acpi_handle_debug(virt_pmc_handle, "_DSM function %u
> evaluation %s\n",
> + ACPI_VIRT_PMC_NOTIFY, out_obj ? "successful" :
> "failed");
> +
> + ACPI_FREE(out_obj);
> +}
> +
> +static struct acpi_s2idle_dev_ops amd_pmc_s2idle_dev_ops = {
> + .check = virt_pmc_s2idle_notify,
> +};
> +
> +static int virt_pmc_probe(struct platform_device *pdev)
> +{
> + int err = 0;
> +
> + virt_pmc_handle = ACPI_HANDLE(&pdev->dev);
> +
> + err = acpi_register_lps0_dev(&amd_pmc_s2idle_dev_ops);
> + if (err)
> + dev_warn(&pdev->dev, "failed to register LPS0 sleep
> handler\n");
> +

Besides registering, I would think you also want to have a query to the
_DSM to determine what functions are available. It could allow this to
scale better if you're going to need to introduce a new function again
later for a different reason.

> + return err;
> +}
> +
> +static int virt_pmc_remove(struct platform_device *pdev)
> +{
> + acpi_unregister_lps0_dev(&amd_pmc_s2idle_dev_ops);
> +
> + return 0;
> +}
> +
> +static const struct acpi_device_id virt_pmc_acpi_ids[] = {
> + {"HYPE0001", 0}, /* _HID for XXX Power Engine, _CID PNP0D80*/
> + { }
> +};
> +MODULE_DEVICE_TABLE(acpi, virt_pmc_acpi_ids);
> +
> +static struct platform_driver virt_pmc_driver = {
> + .driver = {
> + .name = "virtual_pmc",
> + .acpi_match_table = ACPI_PTR(virt_pmc_acpi_ids),
> + },
> + .probe = virt_pmc_probe,
> + .remove = virt_pmc_remove,
> +};
> +
> +module_platform_driver(virt_pmc_driver);
> +
> +MODULE_DESCRIPTION("Virtual PMC Driver");
> --
> 2.39.1.519.gcb327c4b5f-goog