On Fri, Jun 14, 2019 at 10:19:02PM +0000, Dexuan Cui wrote: > > -----Original Message----- > > From: Michael Kelley <[email protected]> > > Sent: Friday, June 14, 2019 1:48 PM > > To: Dexuan Cui <[email protected]>; [email protected]; > > [email protected]; [email protected]; [email protected]; > > [email protected] > > Cc: [email protected]; [email protected]; KY > > Srinivasan > > <[email protected]>; Stephen Hemminger <[email protected]>; > > Haiyang Zhang <[email protected]>; Sasha Levin > > <[email protected]>; [email protected]; [email protected]; > > [email protected]; vkuznets <[email protected]>; > > [email protected] > > Subject: RE: [PATCH] ACPI: PM: Export the function > > acpi_sleep_state_supported() > > > > From: Dexuan Cui <[email protected]> Sent: Friday, June 14, 2019 11:19 > > AM > > > > > > In a Linux VM running on Hyper-V, when ACPI S4 is enabled, the balloon > > > driver (drivers/hv/hv_balloon.c) needs to ask the host not to do memory > > > hot-add/remove. > > > > > > So let's export acpi_sleep_state_supported() for the hv_balloon driver. > > > This might also be useful to the other drivers in the future. > > > > > > Signed-off-by: Dexuan Cui <[email protected]> > > > --- > > > drivers/acpi/sleep.c | 3 ++- > > > include/acpi/acpi_bus.h | 2 ++ > > > 2 files changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c > > > index a34deccd7317..69755411e008 100644 > > > --- a/drivers/acpi/sleep.c > > > +++ b/drivers/acpi/sleep.c > > > @@ -79,7 +79,7 @@ static int acpi_sleep_prepare(u32 acpi_state) > > > return 0; > > > } > > > > > > -static bool acpi_sleep_state_supported(u8 sleep_state) > > > +bool acpi_sleep_state_supported(u8 sleep_state) > > > { > > > acpi_status status; > > > u8 type_a, type_b; > > > @@ -89,6 +89,7 @@ static bool acpi_sleep_state_supported(u8 sleep_state) > > > || (acpi_gbl_FADT.sleep_control.address > > > && acpi_gbl_FADT.sleep_status.address)); > > > } > > > +EXPORT_SYMBOL_GPL(acpi_sleep_state_supported); > > > > > > #ifdef CONFIG_ACPI_SLEEP > > > static u32 acpi_target_sleep_state = ACPI_STATE_S0; > > > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h > > > index 31b6c87d6240..5b102e7bbf25 100644 > > > --- a/include/acpi/acpi_bus.h > > > +++ b/include/acpi/acpi_bus.h > > > @@ -651,6 +651,8 @@ static inline int acpi_pm_set_bridge_wakeup(struct > > device *dev, > > > bool enable) > > > } > > > #endif > > > > > > +bool acpi_sleep_state_supported(u8 sleep_state); > > > + > > > #ifdef CONFIG_ACPI_SLEEP > > > u32 acpi_target_system_state(void); > > > #else > > > -- > > > 2.19.1 > > > > It seems that sleep.c isn't built when on the ARM64 architecture. Using > > acpi_sleep_state_supported() directly in hv_balloon.c will be problematic > > since hv_balloon.c needs to be architecture independent when the > > Hyper-V ARM64 support is added. If that doesn't change, a per-architecture > > wrapper will be needed to give hv_balloon.c the correct information. This > > may affect whether acpi_sleep_state_supported() needs to be exported vs. > > just removing the "static". I'm not sure what the best approach is. > > > > Michael > > + some ARM experts who worked on arch/arm/kernel/hibernate.c. > > drivers/acpi/sleep.c is only built if ACPI_SYSTEM_POWER_STATES_SUPPORT > is defined, but it looks this option is not defined on ARM. > > It looks ARM does not support the ACPI S4 state, then how do we know > if an ARM host supports hibernation or not?
Maybe we should start from understanding why you need to know whether Hibernate is possible to answer your question ? On ARM64 platforms system states are entered through PSCI firmware interface that works for ACPI and device tree alike. Lorenzo
