linux-kernel - Re: [RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for S2Idle

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Date:   Fri, 10 Feb 2023 11:58:39 +0100
From:   Grzegorz Jaszczyk <jaz@...ihalf.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, rafael@...nel.org, dmy@...ihalf.com,
        tn@...ihalf.com, dbehr@...gle.com,
        zide.chen@...el.corp-partner.google.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
Subject: Re: [RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for S2Idle

czw., 9 lut 2023 o 22:26 Sean Christopherson <seanjc@...gle.com> napisał(a):
>
> On Thu, Feb 09, 2023, Grzegorz Jaszczyk wrote:
> > 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()
> > ---
> >  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"
>
> Maybe spell out "Virtual Power Management Controller"?  See below.

Sure, it makes sense to be more verbose here.

>
> > +     depends on ACPI && SUSPEND
>
> I think it makes sense to take a dependency on HYPERVISOR_GUEST.  It's not strictly
> required, but taking that dependency helps clarify that this is a guest-side thing,
> e.g. "virtual PMC" in KVM-land means "virtual performance monitoring counter".
>
> And IMO, disabling HYPERVISOR_GUEST should disable these type of guest-specific
> features.

Ok, thank you