From:   "Limonciello, Mario" <Mario.Limonciello@amd.com>
To:     Grzegorz Jaszczyk <jaz@semihalf.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "rafael@kernel.org" <rafael@kernel.org>
CC:     "dmy@semihalf.com" <dmy@semihalf.com>,
        "tn@semihalf.com" <tn@semihalf.com>,
        "dbehr@google.com" <dbehr@google.com>,
        "zide.chen@intel.corp-partner.google.com" 
        <zide.chen@intel.corp-partner.google.com>,
        "seanjc@google.com" <seanjc@google.com>,
        "upstream@semihalf.com" <upstream@semihalf.com>,
        "hdegoede@redhat.com" <hdegoede@redhat.com>,
        "markgross@kernel.org" <markgross@kernel.org>,
        "dtor@google.com" <dtor@google.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "platform-driver-x86@vger.kernel.org" 
        <platform-driver-x86@vger.kernel.org>
Subject: RE: [RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for
 S2Idle
Thread-Topic: [RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for
 S2Idle
Thread-Index: AQHZPJo6TXhZgi1Iw0Sny1/s70pc067G7lAQ
Date:   Thu, 9 Feb 2023 18:25:38 +0000
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References: <20230209152123.3186930-1-jaz@semihalf.com>
 <20230209152123.3186930-2-jaz@semihalf.com>
In-Reply-To: <20230209152123.3186930-2-jaz@semihalf.com>
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[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
>=20
> 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.
>=20
> 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.
>=20
> 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
>=20
> 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.
>=20
> +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
>=20
>  config P2SB
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefil=
e
> index 1d3d1b02541b..c4d3056cf4ea 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -129,6 +129,9 @@ obj-$(CONFIG_INTEL_SCU_WDT)		+=3D
> intel_scu_wdt.o
>  obj-$(CONFIG_INTEL_SCU_IPC_UTIL)	+=3D intel_scu_ipcutil.o
>  obj-$(CONFIG_X86_INTEL_LPSS)		+=3D pmc_atom.o
>=20
> +# Virtual PMC
> +obj-$(CONFIG_VIRT_PMC)			+=3D virt_pmc.o
> +
>  # Siemens Simatic Industrial PCs
>  obj-$(CONFIG_SIEMENS_SIMATIC_IPC)	+=3D simatic-ipc.o
>=20
> 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 =3D 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 =3D {
> +	.check =3D virt_pmc_s2idle_notify,
> +};
> +
> +static int virt_pmc_probe(struct platform_device *pdev)
> +{
> +	int err =3D 0;
> +
> +	virt_pmc_handle =3D ACPI_HANDLE(&pdev->dev);
> +
> +	err =3D 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[] =3D {
> +	{"HYPE0001", 0}, /* _HID for XXX Power Engine, _CID PNP0D80*/
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, virt_pmc_acpi_ids);
> +
> +static struct platform_driver virt_pmc_driver =3D {
> +	.driver =3D {
> +		.name =3D "virtual_pmc",
> +		.acpi_match_table =3D ACPI_PTR(virt_pmc_acpi_ids),
> +	},
> +	.probe =3D virt_pmc_probe,
> +	.remove =3D virt_pmc_remove,
> +};
> +
> +module_platform_driver(virt_pmc_driver);
> +
> +MODULE_DESCRIPTION("Virtual PMC Driver");
> --
> 2.39.1.519.gcb327c4b5f-goog