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x86/hyperv: Add support for detecting nested hypervisor

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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: Jinank Jain <jinankjain@linux.microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/8e3e7112806e81d2292a66a56fe547162754ecea.1672639707.git.jinankjain@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Jinank Jain 2023-01-02 07:12:51 +00:00 committed by Wei Liu
parent b7bfaa761d
commit c4bdf94f97
4 changed files with 17 additions and 3 deletions
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3
arch/x86/include/asm/hyperv-tlfs.h
View file

@ -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)

7
arch/x86/kernel/cpu/mshyperv.c
View file

@ -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.
*/

9
drivers/hv/hv_common.c
View file

@ -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);

1
include/asm-generic/mshyperv.h
View file

@ -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;