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From:   Grzegorz Jaszczyk <jaz@semihalf.com>
Date:   Wed, 29 Mar 2023 14:33:51 +0200
Message-ID: <CAH76GKOHMtwE7rLTPKUZJ_7xUUdHmHnGyZOsh8pFWoHCiWQynw@mail.gmail.com>
Subject: Re: [RFCv3 1/1] platform/x86: Add virtual PMC driver used for S2Idle
To:     linux-kernel@vger.kernel.org, hdegoede@redhat.com
Cc:     dmy@semihalf.com, tn@semihalf.com, dbehr@google.com,
        zide.chen@intel.corp-partner.google.com, seanjc@google.com,
        upstream@semihalf.com, markgross@kernel.org, dtor@google.com,
        mario.limonciello@amd.com, linux-pm@vger.kernel.org,
        x86@kernel.org, platform-driver-x86@vger.kernel.org,
        rafael@kernel.org
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Hi Hans,

Do you think that this RFC is in good enough state to start the ACPI
ID registration process so after it will be completed we could land
this solution? Or maybe we could land it (of course if there are no
other remarks) even before and adjust if needed?

Thank you in advance,
Grzegorz


pon., 13 lut 2023 o 11:11 Grzegorz Jaszczyk <jaz@semihalf.com> napisa=C5=82=
(a):
>
> 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()
>
> 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/Makefil=
e
> index 1d3d1b02541b..c4d3056cf4ea 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -129,6 +129,9 @@ obj-$(CONFIG_INTEL_SCU_WDT)         +=3D intel_scu_wd=
t.o
>  obj-$(CONFIG_INTEL_SCU_IPC_UTIL)       +=3D intel_scu_ipcutil.o
>  obj-$(CONFIG_X86_INTEL_LPSS)           +=3D pmc_atom.o
>
> +# Virtual PMC
> +obj-$(CONFIG_VIRT_PMC)                 +=3D virt_pmc.o
> +
>  # Siemens Simatic Industrial PCs
>  obj-$(CONFIG_SIEMENS_SIMATIC_IPC)      +=3D 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@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;
> +       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 pmc_s2idle_dev_ops =3D {
> +       .check =3D virt_pmc_s2idle_notify,
> +};
> +
> +static int virt_pmc_probe(struct platform_device *pdev)
> +{
> +       int err =3D 0;
> +       guid_t dsm_guid;
> +
> +       virt_pmc_handle =3D 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 =3D acpi_register_lps0_dev(&pmc_s2idle_dev_ops);
> +       if (err)
> +               dev_err(&pdev->dev, "failed to register LPS0 sleep handle=
r\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[] =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_LICENSE("GPL");
> +MODULE_DESCRIPTION("Virtual PMC Driver");
> --
> 2.39.1.581.gbfd45094c4-goog
>