Hyper-V: arm64: Support for repetitive hypercall

This patch adds support for repetitive hyperv hypercall for arm64. This is
already supported for x64. Its mostly bringing arm64 to the same level of
support by unifying the common functionality.

Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>

Author: sunilmut

arch/arm64/hyperv/mshyperv.c

@@ -32,12 +32,37 @@ 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);
+
 static int hv_cpu_init(unsigned int cpu)
 {
+	void **input_arg;
+
+	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	*input_arg = kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+	if (unlikely(!*input_arg))
+		return -ENOMEM;
 	hv_vp_index[cpu] = hv_get_vpreg(HV_REGISTER_VP_INDEX);
 	return 0;
 }
 
+static int hv_cpu_die(unsigned int cpu)
+{
+	void **input_arg;
+	void *input;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	input = *input_arg;
+	*input_arg = NULL;
+	local_irq_restore(flags);
+	kfree(input);
+
+	return 0;
+}
+
 void __init hyperv_early_init(void)
 {
 	struct hv_get_vp_registers_output	result;
@@ -95,23 +120,35 @@ static int __init hyperv_init(void)
 	if (!hyperv_initialized)
 		return 0;
 
+	/*
+	 * 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 *);
+	if (unlikely(!hyperv_pcpu_input_arg))
+		return -ENOMEM;
+
 	/* Allocate and initialize percpu VP index array */
 	hv_max_vp_index = num_possible_cpus();
 	hv_vp_index = kmalloc_array(hv_max_vp_index, sizeof(*hv_vp_index),
 				    GFP_KERNEL);
 	if (!hv_vp_index) {
 		hv_max_vp_index = 0;
+		free_percpu(hyperv_pcpu_input_arg);
 		return -ENOMEM;
 	}
 
 	for (i = 0; i < hv_max_vp_index; i++)
 		hv_vp_index[i] = VP_INVAL;
 
 	if (cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm64/hyperv_init:online",
-					hv_cpu_init, NULL) < 0) {
+					hv_cpu_init, hv_cpu_die) < 0) {
 		hv_max_vp_index = 0;
 		kfree(hv_vp_index);
 		hv_vp_index = NULL;
+		free_percpu(hyperv_pcpu_input_arg);
 		return -EINVAL;
 	}
 

arch/arm64/include/asm/mshyperv.h

@@ -41,6 +41,7 @@ extern u64 hv_do_hvc_fast_get(u64 control, u64 input1, u64 input2, u64 input3,
 extern void hv_set_vpreg(u32 reg, u64 value);
 extern u64 hv_get_vpreg(u32 reg);
 extern void hv_get_vpreg_128(u32 reg, struct hv_get_vp_registers_output *result);
+extern void __percpu **hyperv_pcpu_input_arg;
 
 static inline void hv_set_register(unsigned int reg, u64 value)
 {

arch/x86/include/asm/mshyperv.h

@@ -140,38 +140,6 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
 	return hv_status;
 }
 
-/*
- * Rep hypercalls. Callers of this functions are supposed to ensure that
- * rep_count and varhead_size comply with Hyper-V hypercall definition.
- */
-static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
-				      void *input, void *output)
-{
-	u64 control = code;
-	u64 status;
-	u16 rep_comp;
-
-	control |= (u64)varhead_size << HV_HYPERCALL_VARHEAD_OFFSET;
-	control |= (u64)rep_count << HV_HYPERCALL_REP_COMP_OFFSET;
-
-	do {
-		status = hv_do_hypercall(control, input, output);
-		if ((status & HV_HYPERCALL_RESULT_MASK) != HV_STATUS_SUCCESS)
-			return status;
-
-		/* Bits 32-43 of status have 'Reps completed' data. */
-		rep_comp = (status & HV_HYPERCALL_REP_COMP_MASK) >>
-			HV_HYPERCALL_REP_COMP_OFFSET;
-
-		control &= ~HV_HYPERCALL_REP_START_MASK;
-		control |= (u64)rep_comp << HV_HYPERCALL_REP_START_OFFSET;
-
-		touch_nmi_watchdog();
-	} while (rep_comp < rep_count);
-
-	return status;
-}
-
 extern struct hv_vp_assist_page **hv_vp_assist_page;
 
 static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int cpu)

include/asm-generic/mshyperv.h

@@ -22,6 +22,7 @@
 #include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/cpumask.h>
+#include <linux/nmi.h>
 #include <asm/ptrace.h>
 #include <asm/hyperv-tlfs.h>
 
@@ -168,6 +169,38 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
 	return nr_bank;
 }
 
+/*
+ * Rep hypercalls. Callers of this functions are supposed to ensure that
+ * rep_count and varhead_size comply with Hyper-V hypercall definition.
+ */
+static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
+				      void *input, void *output)
+{
+	u64 control = code;
+	u64 status;
+	u16 rep_comp;
+
+	control |= (u64)varhead_size << HV_HYPERCALL_VARHEAD_OFFSET;
+	control |= (u64)rep_count << HV_HYPERCALL_REP_COMP_OFFSET;
+
+	do {
+		status = hv_do_hypercall(control, input, output);
+		if ((status & HV_HYPERCALL_RESULT_MASK) != HV_STATUS_SUCCESS)
+			return status;
+
+		/* Bits 32-43 of status have 'Reps completed' data. */
+		rep_comp = (status & HV_HYPERCALL_REP_COMP_MASK) >>
+			HV_HYPERCALL_REP_COMP_OFFSET;
+
+		control &= ~HV_HYPERCALL_REP_START_MASK;
+		control |= (u64)rep_comp << HV_HYPERCALL_REP_START_OFFSET;
+
+		touch_nmi_watchdog();
+	} while (rep_comp < rep_count);
+
+	return status;
+}
+
 void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
 bool hv_is_hyperv_initialized(void);
 bool hv_is_hibernation_supported(void);