On Thursday, July 4, 2019 4:43:32 AM CEST Dexuan Cui wrote: > > With some upcoming patches to save/restore the Hyper-V drivers related > states, a Linux VM running on Hyper-V will be able to hibernate. When > a Linux VM hibernates, unluckily we must disable the memory hot-add/remove > and balloon up/down capabilities in the hv_balloon driver > (drivers/hv/hv_balloon.c), because these can not really work according to > the design of the related back-end driver on the host. > > By default, Hyper-V does not enable the virtual ACPI S4 state for a VM; > on recent Hyper-V hosts, the administrator is able to enable the virtual > ACPI S4 state for a VM, so we hope to use the presence of the virtual ACPI > S4 state as a hint for hv_balloon to disable the aforementioned > capabilities. In this way, hibernation will work more reliably, from the > user's perspective. > > By marking acpi_sleep_state_supported() non-static, we'll be able to > implement a hv_is_hibernation_supported() API in the always-built-in > module arch/x86/hyperv/hv_init.c, and the API will be called by hv_balloon. > > Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx> > --- > > Previously I posted a version that tries to export the function: > https://lkml.org/lkml/2019/6/14/1077, which may be an overkill. > > So I proposed a second patch (which covers this patch and shows how this > patch will be used): https://lkml.org/lkml/2019/6/19/861 > > I explained the situation in detail here: https://lkml.org/lkml/2019/6/21/63 > (a correction: old Hyper-V hosts can support guest hibernation, but some > important functionalities in the host's management tool stack are missing). > > There is no further reply in that discussion, so I'm sending this patch to > draw people's attention again. :-) > > drivers/acpi/sleep.c | 2 +- > include/acpi/acpi_bus.h | 6 ++++++ > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c > index 8ff08e531443..d1ff303a857a 100644 > --- a/drivers/acpi/sleep.c > +++ b/drivers/acpi/sleep.c > @@ -77,7 +77,7 @@ 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; > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h > index 31b6c87d6240..3e6563e1a2c0 100644 > --- a/include/acpi/acpi_bus.h > +++ b/include/acpi/acpi_bus.h > @@ -651,6 +651,12 @@ static inline int acpi_pm_set_bridge_wakeup(struct device *dev, bool enable) > } > #endif > > +#ifdef CONFIG_ACPI_SYSTEM_POWER_STATES_SUPPORT > +bool acpi_sleep_state_supported(u8 sleep_state); > +#else > +bool acpi_sleep_state_supported(u8 sleep_state) { return false; } > +#endif > + > #ifdef CONFIG_ACPI_SLEEP > u32 acpi_target_system_state(void); > #else > Applied, thanks!
