Commit e9977202 authored by Wei Liu's avatar Wei Liu

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
......@@ -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
......
......@@ -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);
......
......@@ -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.
*/
......
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