Hyper-V: Support for querying extended capabilities

This patch adds support for querying extended Hyper-V
capabilities using the extended hypercall.

Signed-off-by: Sunil Muthuswamy <[email protected]>

TAG_MSFT: wsl

Author: sunilmut

arch/arm64/hyperv/hv_core.c

@@ -159,13 +159,15 @@ static int __init hyperv_init(struct acpi_table_header *table)
 	/* Get the features and hints from Hyper-V */
 	hv_get_vpreg_128(HV_REGISTER_FEATURES, &result);
 	ms_hyperv.features = result.as32.a;
+	ms_hyperv.priv_high = result.as32.b;
 	ms_hyperv.misc_features = result.as32.c;
 
 	hv_get_vpreg_128(HV_REGISTER_ENLIGHTENMENTS, &result);
 	ms_hyperv.hints = result.as32.a;
 
-	pr_info("Hyper-V: Features 0x%x, hints 0x%x, misc 0x%x\n",
-		ms_hyperv.features, ms_hyperv.hints, ms_hyperv.misc_features);
+	pr_info("Hyper-V: Features 0x%x, privilege high: 0x%x, hints 0x%x, misc 0x%x\n",
+		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
+		ms_hyperv.misc_features);
 
 	/*
 	 * Allocate the per-CPU state for the hypercall input arg.

arch/x86/kernel/cpu/mshyperv.c

@@ -225,11 +225,13 @@ static void __init ms_hyperv_init_platform(void)
 	 * Extract the features and hints
 	 */
 	ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
+	ms_hyperv.priv_high = cpuid_ebx(HYPERV_CPUID_FEATURES);
 	ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
 	ms_hyperv.hints    = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
 
-	pr_info("Hyper-V: features 0x%x, hints 0x%x, misc 0x%x\n",
-		ms_hyperv.features, ms_hyperv.hints, ms_hyperv.misc_features);
+	pr_info("Hyper-V: features 0x%x, privilege high: 0x%x, hints 0x%x, misc 0x%x\n",
+		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
+		ms_hyperv.misc_features);
 
 	ms_hyperv.max_vp_index = cpuid_eax(HYPERV_CPUID_IMPLEMENT_LIMITS);
 	ms_hyperv.max_lp_index = cpuid_ebx(HYPERV_CPUID_IMPLEMENT_LIMITS);

include/asm-generic/hyperv-tlfs.h

@@ -89,6 +89,7 @@
 #define HV_ACCESS_STATS				BIT(8)
 #define HV_DEBUGGING				BIT(11)
 #define HV_CPU_POWER_MANAGEMENT			BIT(12)
+#define HV_ENABLE_EXTENDED_HYPERCALLS           BIT(20)
 
 
 /*
@@ -151,6 +152,7 @@ struct ms_hyperv_tsc_page {
 #define HVCALL_RETARGET_INTERRUPT		0x007e
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
+#define HVCALL_QUERY_CAPABILITIES		0x8001
 
 #define HV_FLUSH_ALL_PROCESSORS			BIT(0)
 #define HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES	BIT(1)

include/asm-generic/mshyperv.h

@@ -28,6 +28,7 @@
 
 struct ms_hyperv_info {
 	u32 features;
+	u32 priv_high;
 	u32 misc_features;
 	u32 hints;
 	u32 nested_features;
@@ -217,6 +218,35 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
 
 	return status;
 }
+
+static inline bool hyperv_query_ext_cap(u64 cap_to_query)
+{
+	u64 *cap;
+	unsigned long flags;
+	u64 status;
+
+	/*
+	 * Querying extended capabilities is done via an extended hypercall.
+	 * Check if the partition supports extended hypercall, first.
+	 */
+	if (!(ms_hyperv.priv_high & HV_ENABLE_EXTENDED_HYPERCALLS)) {
+		pr_info("Hyper-V doesn't support extended hypercalls\n");
+		return 0;
+	}
+
+	local_irq_save(flags);
+	cap = *(u64 **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	status = hv_do_hypercall(HVCALL_QUERY_CAPABILITIES, NULL, cap)
+			& HV_HYPERCALL_RESULT_MASK;
+	local_irq_restore(flags);
+	if (status != HV_STATUS_SUCCESS) {
+		pr_err("Extended cap query hypercall failed: 0x%llx\n", status);
+		return 0;
+	}
+
+	return (*cap & cap_to_query);
+}
+
 #endif
 
 #endif