lkml.org 
[lkml]   [2020]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH RFC v1 02/18] x86/hyperv: detect if Linux is the root partition
Date
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 <wei.liu@kernel.org>
---
arch/x86/hyperv/hv_init.c | 4 ++++
arch/x86/include/asm/hyperv-tlfs.h | 10 ++++++++++
arch/x86/include/asm/mshyperv.h | 2 ++
arch/x86/kernel/cpu/mshyperv.c | 16 ++++++++++++++++
4 files changed, 32 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 6035df1b49e1..cac8e4c56261 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -26,6 +26,10 @@
#include <linux/syscore_ops.h>
#include <clocksource/hyperv_timer.h>

+/* Is Linux running as the root partition? */
+bool hv_root_partition;
+EXPORT_SYMBOL_GPL(hv_root_partition);
+
void *hv_hypercall_pg;
EXPORT_SYMBOL_GPL(hv_hypercall_pg);

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 7a4d2062385c..20d628c1ed50 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_HYPERVISOR_PRESENT_BIT 0x80000000
@@ -136,6 +137,15 @@
/* 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 60b944dd2df1..2a2cc81beac6 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -224,6 +224,8 @@ 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 af94f05a5c66..1bf57d310f78 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -232,6 +232,22 @@ 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.
*/
--
2.20.1
\
 
 \ /
  Last update: 2020-09-14 19:51    [W:0.123 / U:10.568 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site