Commit c4bdf94f authored by Jinank Jain's avatar Jinank Jain Committed by Wei Liu
Browse files

x86/hyperv: Add support for detecting nested hypervisor 



Detect if Linux is running as a nested hypervisor in the root
partition for Microsoft Hypervisor, using flags provided by MSHV.
Expose a new variable hv_nested that is used later for decisions
specific to the nested use case.

Signed-off-by: default avatarJinank Jain <jinankjain@linux.microsoft.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/8e3e7112806e81d2292a66a56fe547162754ecea.1672639707.git.jinankjain@linux.microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent b7bfaa76

arch/x86/include/asm/hyperv-tlfs.h

+3 −0
Original line number Diff line number Diff line
@@ -116,6 +116,9 @@ 
/* Recommend using the newer ExProcessorMasks interface */

#define HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED		BIT(11)



/* Indicates that the hypervisor is nested within a Hyper-V partition. */

#define HV_X64_HYPERV_NESTED				BIT(12)



/* Recommend using enlightened VMCS */

#define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED		BIT(14)

arch/x86/kernel/cpu/mshyperv.c

+7 −0
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ 


/* Is Linux running as the root partition? */

bool hv_root_partition;

/* Is Linux running on nested Microsoft Hypervisor */

bool hv_nested;

struct ms_hyperv_info ms_hyperv;



#if IS_ENABLED(CONFIG_HYPERV)
@@ -301,6 +303,11 @@ static void __init ms_hyperv_init_platform(void) 
		pr_info("Hyper-V: running as root partition\n");

	}



	if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {

		hv_nested = true;

		pr_info("Hyper-V: running on a nested hypervisor\n");

	}



	/*

	 * Extract host information.

	 */

drivers/hv/hv_common.c

+6 −3
Original line number Diff line number Diff line
@@ -25,17 +25,20 @@ 
#include <asm/mshyperv.h>



/*

 * hv_root_partition and ms_hyperv are defined here with other Hyper-V

 * specific globals so they are shared across all architectures and are

 * hv_root_partition, ms_hyperv and hv_nested are defined here with other

 * Hyper-V specific globals so they are shared across all architectures and are

 * built only when CONFIG_HYPERV is defined.  But on x86,

 * ms_hyperv_init_platform() is built even when CONFIG_HYPERV is not

 * defined, and it uses these two variables.  So mark them as __weak

 * defined, and it uses these three variables.  So mark them as __weak

 * here, allowing for an overriding definition in the module containing

 * ms_hyperv_init_platform().

 */

bool __weak hv_root_partition;

EXPORT_SYMBOL_GPL(hv_root_partition);



bool __weak hv_nested;

EXPORT_SYMBOL_GPL(hv_nested);



struct ms_hyperv_info __weak ms_hyperv;

EXPORT_SYMBOL_GPL(ms_hyperv);

include/asm-generic/mshyperv.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ struct ms_hyperv_info { 
	u64 shared_gpa_boundary;

};

extern struct ms_hyperv_info ms_hyperv;

extern bool hv_nested;



extern void * __percpu *hyperv_pcpu_input_arg;

extern void * __percpu *hyperv_pcpu_output_arg;