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Message-ID: <c5455226-1d51-1d3d-0b67-78a0473a9e8c@redhat.com>
Date:   Thu, 6 Apr 2023 12:53:37 +0200
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Subject: Re: [RFCv3 1/1] platform/x86: Add virtual PMC driver used for S2Idle
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To:     Grzegorz Jaszczyk <jaz@semihalf.com>, linux-kernel@vger.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, 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
References: <20230213100921.268770-1-jaz@semihalf.com>
 <20230213100921.268770-2-jaz@semihalf.com>
 <CAH76GKOHMtwE7rLTPKUZJ_7xUUdHmHnGyZOsh8pFWoHCiWQynw@mail.gmail.com>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <CAH76GKOHMtwE7rLTPKUZJ_7xUUdHmHnGyZOsh8pFWoHCiWQynw@mail.gmail.com>
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Hi Grzegorz,

On 3/29/23 14:33, Grzegorz Jaszczyk wrote:
> 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?

I see from the links in the cover-letter that most of
the previous discussion has happened on the linux-pm list
and I believe that the linux-pm folks are in a better place
to answer this question then I am.

I have no objections against the suggested approach,
but I don't really feel that it is my call to make if
we should move forward with this.

Regards,

Hans


> pon., 13 lut 2023 o 11:11 Grzegorz Jaszczyk <jaz@semihalf.com> napisał(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/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@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 = 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
>>
>