Commit e9977202 authored by Wei Liu's avatar Wei Liu
Browse files

x86/hyperv: detect if Linux is the root partition 



For now we can use the privilege flag to check. Stash the value to be
used later.

Put in a bunch of defines for future use when we want to have more
fine-grained detection.

Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Reviewed-by: default avatarPavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20210203150435.27941-3-wei.liu@kernel.org
parent 8f1d14cb

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

+10 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#define HYPERV_CPUID_FEATURES			0x40000003

#define HYPERV_CPUID_ENLIGHTMENT_INFO		0x40000004

#define HYPERV_CPUID_IMPLEMENT_LIMITS		0x40000005

#define HYPERV_CPUID_CPU_MANAGEMENT_FEATURES	0x40000007

#define HYPERV_CPUID_NESTED_FEATURES		0x4000000A

#define HYPERV_CPUID_ISOLATION_CONFIG		0x4000000C
@@ -111,6 +112,15 @@ 
/* Recommend using enlightened VMCS */

#define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED		BIT(14)



/*

 * CPU management features identification.

 * These are HYPERV_CPUID_CPU_MANAGEMENT_FEATURES.EAX bits.

 */

#define HV_X64_START_LOGICAL_PROCESSOR			BIT(0)

#define HV_X64_CREATE_ROOT_VIRTUAL_PROCESSOR		BIT(1)

#define HV_X64_PERFORMANCE_COUNTER_SYNC			BIT(2)

#define HV_X64_RESERVED_IDENTITY_BIT			BIT(31)



/*

 * Virtual processor will never share a physical core with another virtual

 * processor, except for virtual processors that are reported as sibling SMT

arch/x86/include/asm/mshyperv.h

+2 −0
Original line number Diff line number Diff line
@@ -239,6 +239,8 @@ int hyperv_fill_flush_guest_mapping_list( 
		struct hv_guest_mapping_flush_list *flush,

		u64 start_gfn, u64 end_gfn);



extern bool hv_root_partition;



#ifdef CONFIG_X86_64

void hv_apic_init(void);

void __init hv_init_spinlocks(void);

arch/x86/kernel/cpu/mshyperv.c

+20 −0
Original line number Diff line number Diff line
@@ -32,6 +32,10 @@ 
#include <asm/nmi.h>

#include <clocksource/hyperv_timer.h>



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

bool hv_root_partition;

EXPORT_SYMBOL_GPL(hv_root_partition);



struct ms_hyperv_info ms_hyperv;

EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -256,6 +260,22 @@ static void __init ms_hyperv_init_platform(void) 
	pr_debug("Hyper-V: max %u virtual processors, %u logical processors\n",

		 ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);



	/*

	 * Check CPU management privilege.

	 *

	 * To mirror what Windows does we should extract CPU management

	 * features and use the ReservedIdentityBit to detect if Linux is the

	 * root partition. But that requires negotiating CPU management

	 * interface (a process to be finalized).

	 *

	 * For now, use the privilege flag as the indicator for running as

	 * root.

	 */

	if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_CPU_MANAGEMENT) {

		hv_root_partition = true;

		pr_info("Hyper-V: running as root partition\n");

	}



	/*

	 * Extract host information.

	 */