RE: [PATCH 1/7] x86/hyper-v: Suspend/resume the hypercall page for hibernation

[Michael Kelley <mikelley@microsoft.com>]

From: Dexuan Cui <decui@microsoft.com> Sent: Monday, July 8, 2019 10:29 PM
> 
> This is needed for hibernation, e.g. when we resume the old kernel, we need
> to disable the "current" kernel's hypercall page and then resume the old
> kernel's.
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
>  arch/x86/hyperv/hv_init.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 0e033ef..3005871 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -20,6 +20,7 @@
>  #include <linux/hyperv.h>
>  #include <linux/slab.h>
>  #include <linux/cpuhotplug.h>
> +#include <linux/syscore_ops.h>
>  #include <clocksource/hyperv_timer.h>
> 
>  void *hv_hypercall_pg;
> @@ -214,6 +215,34 @@ static int __init hv_pci_init(void)
>  	return 1;
>  }
> 
> +static int hv_suspend(void)
> +{
> +	union hv_x64_msr_hypercall_contents hypercall_msr;
> +
> +	/* Reset the hypercall page */
> +	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +	hypercall_msr.enable = 0;
> +	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +
> +	return 0;
> +}
> +
> +static void hv_resume(void)
> +{
> +	union hv_x64_msr_hypercall_contents hypercall_msr;
> +
> +	/* Re-enable the hypercall page */
> +	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +	hypercall_msr.enable = 1;
> +	hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
> +	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +}
> +
> +static struct syscore_ops hv_syscore_ops = {
> +	.suspend = hv_suspend,
> +	.resume = hv_resume,
> +};
> +
>  /*
>   * This function is to be invoked early in the boot sequence after the
>   * hypervisor has been detected.
> @@ -294,6 +323,9 @@ void __init hyperv_init(void)
> 
>  	/* Register Hyper-V specific clocksource */
>  	hv_init_clocksource();
> +
> +	register_syscore_ops(&hv_syscore_ops);
> +
>  	return;
> 
>  remove_cpuhp_state:
> @@ -313,6 +345,8 @@ void hyperv_cleanup(void)
>  {
>  	union hv_x64_msr_hypercall_contents hypercall_msr;
> 
> +	unregister_syscore_ops(&hv_syscore_ops);
> +
>  	/* Reset our OS id */
>  	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
> 
> --
> 1.8.3.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>