From e997720202b363ba8000d769f114e3c2c5822227 Mon Sep 17 00:00:00 2001 From: Wei Liu Date: Wed, 3 Feb 2021 15:04:21 +0000 Subject: [PATCH] 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: Wei Liu Reviewed-by: Pavel Tatashin Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20210203150435.27941-3-wei.liu@kernel.org --- arch/x86/include/asm/hyperv-tlfs.h | 10 ++++++++++ arch/x86/include/asm/mshyperv.h | 2 ++ arch/x86/kernel/cpu/mshyperv.c | 20 ++++++++++++++++++++ 3 files changed, 32 insertions(+) diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h index 6aed936e5e96..e3a6a723d661 100644 --- a/arch/x86/include/asm/hyperv-tlfs.h +++ b/arch/x86/include/asm/hyperv-tlfs.h @@ -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 diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h index 30f76b966857..4014a1ca2fae 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -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); diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index fc6cb84c9fe5..39a4b4509b87 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -32,6 +32,10 @@ #include #include +/* 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. */