Drivers: hv: Make portions of Hyper-V init code be arch neutral

The code to allocate and initialize the hv_vp_index array is
architecture neutral. Similarly, the code to allocate and
populate the hypercall input and output arg pages is architecture
neutral.  Move both sets of code out from arch/x86 and into
utility functions in drivers/hv/hv_common.c that can be shared
by Hyper-V initialization on ARM64.

No functional changes. However, the allocation of the hypercall
input and output arg pages is done differently so that the
size is always the Hyper-V page size, even if not the same as
the guest page size (such as with ARM64's 64K page size).

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1626287687-2045-2-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

arch/x86/hyperv/hv_init.c

@@ -39,48 +39,17 @@ EXPORT_SYMBOL_GPL(hv_hypercall_pg);
 /* Storage to save the hypercall page temporarily for hibernation */
 static void *hv_hypercall_pg_saved;
 
-u32 *hv_vp_index;
-EXPORT_SYMBOL_GPL(hv_vp_index);
-
 struct hv_vp_assist_page **hv_vp_assist_page;
 EXPORT_SYMBOL_GPL(hv_vp_assist_page);
 
-void  __percpu **hyperv_pcpu_input_arg;
-EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
-
-void  __percpu **hyperv_pcpu_output_arg;
-EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
-
-u32 hv_max_vp_index;
-EXPORT_SYMBOL_GPL(hv_max_vp_index);
-
 static int hv_cpu_init(unsigned int cpu)
 {
-	u64 msr_vp_index;
 	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
-	void **input_arg;
+	int ret;
-	struct page *pg;
 
-	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
+	ret = hv_common_cpu_init(cpu);
-	pg = alloc_pages(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL, hv_root_partition ? 1 : 0);
+	if (ret)
-	if (unlikely(!pg))
+		return ret;
-		return -ENOMEM;
-
-	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
-	*input_arg = page_address(pg);
-	if (hv_root_partition) {
-		void **output_arg;
-
-		output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
-		*output_arg = page_address(pg + 1);
-	}
-
-	msr_vp_index = hv_get_register(HV_REGISTER_VP_INDEX);
-
-	hv_vp_index[smp_processor_id()] = msr_vp_index;
-
-	if (msr_vp_index > hv_max_vp_index)
-		hv_max_vp_index = msr_vp_index;
 
 	if (!hv_vp_assist_page)
 		return 0;
@@ -198,25 +167,8 @@ static int hv_cpu_die(unsigned int cpu)
 {
 	struct hv_reenlightenment_control re_ctrl;
 	unsigned int new_cpu;
-	unsigned long flags;
-	void **input_arg;
-	void *pg;
 
-	local_irq_save(flags);
+	hv_common_cpu_die(cpu);
-	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
-	pg = *input_arg;
-	*input_arg = NULL;
-
-	if (hv_root_partition) {
-		void **output_arg;
-
-		output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
-		*output_arg = NULL;
-	}
-
-	local_irq_restore(flags);
-
-	free_pages((unsigned long)pg, hv_root_partition ? 1 : 0);
 
 	if (hv_vp_assist_page && hv_vp_assist_page[cpu])
 		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
@@ -368,7 +320,7 @@ void __init hyperv_init(void)
 {
 	u64 guest_id, required_msrs;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
-	int cpuhp, i;
+	int cpuhp;
 
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;
@@ -380,36 +332,14 @@ void __init hyperv_init(void)
 	if ((ms_hyperv.features & required_msrs) != required_msrs)
 		return;
 
-	/*
+	if (hv_common_init())
-	 * Allocate the per-CPU state for the hypercall input arg.
-	 * If this allocation fails, we will not be able to setup
-	 * (per-CPU) hypercall input page and thus this failure is
-	 * fatal on Hyper-V.
-	 */
-	hyperv_pcpu_input_arg = alloc_percpu(void  *);
-
-	BUG_ON(hyperv_pcpu_input_arg == NULL);
-
-	/* Allocate the per-CPU state for output arg for root */
-	if (hv_root_partition) {
-		hyperv_pcpu_output_arg = alloc_percpu(void *);
-		BUG_ON(hyperv_pcpu_output_arg == NULL);
-	}
-
-	/* Allocate percpu VP index */
-	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
-				    GFP_KERNEL);
-	if (!hv_vp_index)
 		return;
 
-	for (i = 0; i < num_possible_cpus(); i++)
-		hv_vp_index[i] = VP_INVAL;
-
 	hv_vp_assist_page = kcalloc(num_possible_cpus(),
 				    sizeof(*hv_vp_assist_page), GFP_KERNEL);
 	if (!hv_vp_assist_page) {
 		ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
-		goto free_vp_index;
+		goto common_free;
 	}
 
 	cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
@@ -507,9 +437,8 @@ remove_cpuhp_state:
 free_vp_assist_page:
 	kfree(hv_vp_assist_page);
 	hv_vp_assist_page = NULL;
-free_vp_index:
+common_free:
-	kfree(hv_vp_index);
+	hv_common_free();
-	hv_vp_index = NULL;
 }
 
 /*

arch/x86/include/asm/mshyperv.h

@@ -36,8 +36,6 @@ void hyperv_vector_handler(struct pt_regs *regs);
 extern int hyperv_init_cpuhp;
 
 extern void *hv_hypercall_pg;
-extern void  __percpu  **hyperv_pcpu_input_arg;
-extern void  __percpu  **hyperv_pcpu_output_arg;
 
 extern u64 hv_current_partition_id;
 
@@ -170,8 +168,6 @@ 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

@@ -36,10 +36,7 @@
 
 /* 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);
 
 #if IS_ENABLED(CONFIG_HYPERV)
 static void (*vmbus_handler)(void);

drivers/hv/hv_common.c

@@ -15,9 +15,147 @@
 #include <linux/types.h>
 #include <linux/export.h>
 #include <linux/bitfield.h>
+#include <linux/cpumask.h>
+#include <linux/slab.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>
 
+/*
+ * hv_root_partition and ms_hyperv are defined here with other Hyper-V
+ * specific globals so they are shared across all architectures and are
+ * built only when CONFIG_HYPERV is defined.  But on x86,
+ * ms_hyperv_init_platform() is built even when CONFIG_HYPERV is not
+ * defined, and it uses these two variables.  So mark them as __weak
+ * here, allowing for an overriding definition in the module containing
+ * ms_hyperv_init_platform().
+ */
+bool __weak hv_root_partition;
+EXPORT_SYMBOL_GPL(hv_root_partition);
+
+struct ms_hyperv_info __weak ms_hyperv;
+EXPORT_SYMBOL_GPL(ms_hyperv);
+
+u32 *hv_vp_index;
+EXPORT_SYMBOL_GPL(hv_vp_index);
+
+u32 hv_max_vp_index;
+EXPORT_SYMBOL_GPL(hv_max_vp_index);
+
+void  __percpu **hyperv_pcpu_input_arg;
+EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
+
+void  __percpu **hyperv_pcpu_output_arg;
+EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
+
+/*
+ * Hyper-V specific initialization and shutdown code that is
+ * common across all architectures.  Called from architecture
+ * specific initialization functions.
+ */
+
+void __init hv_common_free(void)
+{
+	kfree(hv_vp_index);
+	hv_vp_index = NULL;
+
+	free_percpu(hyperv_pcpu_output_arg);
+	hyperv_pcpu_output_arg = NULL;
+
+	free_percpu(hyperv_pcpu_input_arg);
+	hyperv_pcpu_input_arg = NULL;
+}
+
+int __init hv_common_init(void)
+{
+	int i;
+
+	/*
+	 * Allocate the per-CPU state for the hypercall input arg.
+	 * If this allocation fails, we will not be able to setup
+	 * (per-CPU) hypercall input page and thus this failure is
+	 * fatal on Hyper-V.
+	 */
+	hyperv_pcpu_input_arg = alloc_percpu(void  *);
+	BUG_ON(!hyperv_pcpu_input_arg);
+
+	/* Allocate the per-CPU state for output arg for root */
+	if (hv_root_partition) {
+		hyperv_pcpu_output_arg = alloc_percpu(void *);
+		BUG_ON(!hyperv_pcpu_output_arg);
+	}
+
+	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
+				    GFP_KERNEL);
+	if (!hv_vp_index) {
+		hv_common_free();
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < num_possible_cpus(); i++)
+		hv_vp_index[i] = VP_INVAL;
+
+	return 0;
+}
+
+/*
+ * Hyper-V specific initialization and die code for
+ * individual CPUs that is common across all architectures.
+ * Called by the CPU hotplug mechanism.
+ */
+
+int hv_common_cpu_init(unsigned int cpu)
+{
+	void **inputarg, **outputarg;
+	u64 msr_vp_index;
+	gfp_t flags;
+	int pgcount = hv_root_partition ? 2 : 1;
+
+	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
+	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
+
+	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
+	if (!(*inputarg))
+		return -ENOMEM;
+
+	if (hv_root_partition) {
+		outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
+		*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
+	}
+
+	msr_vp_index = hv_get_register(HV_REGISTER_VP_INDEX);
+
+	hv_vp_index[cpu] = msr_vp_index;
+
+	if (msr_vp_index > hv_max_vp_index)
+		hv_max_vp_index = msr_vp_index;
+
+	return 0;
+}
+
+int hv_common_cpu_die(unsigned int cpu)
+{
+	unsigned long flags;
+	void **inputarg, **outputarg;
+	void *mem;
+
+	local_irq_save(flags);
+
+	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	mem = *inputarg;
+	*inputarg = NULL;
+
+	if (hv_root_partition) {
+		outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
+		*outputarg = NULL;
+	}
+
+	local_irq_restore(flags);
+
+	kfree(mem);
+
+	return 0;
+}
 
 /* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
 bool hv_query_ext_cap(u64 cap_query)

include/asm-generic/mshyperv.h

@@ -39,6 +39,9 @@ struct ms_hyperv_info {
 };
 extern struct ms_hyperv_info ms_hyperv;
 
+extern void  __percpu  **hyperv_pcpu_input_arg;
+extern void  __percpu  **hyperv_pcpu_output_arg;
+
 extern u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
 extern u64 hv_do_fast_hypercall8(u16 control, u64 input8);
 
@@ -152,6 +155,8 @@ void hv_remove_crash_handler(void);
 extern int vmbus_interrupt;
 extern int vmbus_irq;
 
+extern bool hv_root_partition;
+
 #if IS_ENABLED(CONFIG_HYPERV)
 /*
  * Hypervisor's notion of virtual processor ID is different from
@@ -165,6 +170,11 @@ extern u32 hv_max_vp_index;
 /* Sentinel value for an uninitialized entry in hv_vp_index array */
 #define VP_INVAL	U32_MAX
 
+int __init hv_common_init(void);
+void __init hv_common_free(void);
+int hv_common_cpu_init(unsigned int cpu);
+int hv_common_cpu_die(unsigned int cpu);
+
 void *hv_alloc_hyperv_page(void);
 void *hv_alloc_hyperv_zeroed_page(void);
 void hv_free_hyperv_page(unsigned long addr);