linux-kernel - [RFCv3 1/1] platform/x86: Add virtual PMC driver used for S2Idle

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Message-Id: <20230213100921.268770-2-jaz@semihalf.com>
Date:   Mon, 13 Feb 2023 10:09:21 +0000
From:   Grzegorz Jaszczyk <jaz@...ihalf.com>
To:     linux-kernel@...r.kernel.org, rafael@...nel.org
Cc:     dmy@...ihalf.com, tn@...ihalf.com, dbehr@...gle.com,
        zide.chen@...el.corp-partner.google.com, seanjc@...gle.com,
        upstream@...ihalf.com, hdegoede@...hat.com, markgross@...nel.org,
        dtor@...gle.com, mario.limonciello@....com,
        linux-pm@...r.kernel.org, x86@...nel.org,
        platform-driver-x86@...r.kernel.org,
        Grzegorz Jaszczyk <jaz@...ihalf.com>
Subject: [RFCv3 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@...ihalf.com>
---
Changelog v1..v2:
- Take advantage of acpi_s2idle_dev_ops's check() instead of notify()

Changelog v2..v3:
- Add MODULE_LICENSE
- Remove "amd" prefixes
- Be more verbose in VIRT_PMC config description and make it
  HYPERVISOR_GUEST dependent
- Add extra check ensuring that DSM method supports ACPI_VIRT_PMC_NOTIFY function
---
 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

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 5692385e2d26..837ce201b68b 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 "Virtual Power Management Controller"
+	depends on ACPI && SUSPEND && HYPERVISOR_GUEST
+	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..a5966bb9048f
--- /dev/null
+++ b/drivers/platform/x86/virt_pmc.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Virtual Power Management Controller Driver
+ *
+ * Author: Grzegorz Jaszczyk <jaz@...ihalf.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;
+	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 pmc_s2idle_dev_ops = {
+	.check = virt_pmc_s2idle_notify,
+};
+
+static int virt_pmc_probe(struct platform_device *pdev)
+{
+	int err = 0;
+	guid_t dsm_guid;
+
+	virt_pmc_handle = ACPI_HANDLE(&pdev->dev);
+
+	guid_parse(ACPI_VIRT_PMC_DSM_UUID, &dsm_guid);
+
+	if (!acpi_check_dsm(virt_pmc_handle, &dsm_guid, 0,
+			    1 << ACPI_VIRT_PMC_NOTIFY)) {
+		dev_err(&pdev->dev, "DSM method doesn't support ACPI_VIRT_PMC_NOTIFY\n");
+		return -ENODEV;
+	}
+
+	err = acpi_register_lps0_dev(&pmc_s2idle_dev_ops);
+	if (err)
+		dev_err(&pdev->dev, "failed to register LPS0 sleep handler\n");
+
+	return err;
+}
+
+static int virt_pmc_remove(struct platform_device *pdev)
+{
+	acpi_unregister_lps0_dev(&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_LICENSE("GPL");
+MODULE_DESCRIPTION("Virtual PMC Driver");
-- 
2.39.1.581.gbfd45094c4-goog