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>

TAG_MSFT: wsl

Author: sunilmut

arch/arm64/hyperv/hv_core.c

@@ -40,10 +40,21 @@ 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;
+	struct page *pg;
 	u64 msr_vp_index;
 
+	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	pg = alloc_page(GFP_KERNEL);
+	if (unlikely(!pg))
+		return -ENOMEM;
+	*input_arg = page_address(pg);
+
 	msr_vp_index = hv_get_vpreg(HV_REGISTER_VPINDEX);
 
 	hv_vp_index[smp_processor_id()] = msr_vp_index;
@@ -54,6 +65,22 @@ static int hv_cpu_init(unsigned int cpu)
 	return 0;
 }
 
+static int hv_cpu_die(unsigned int cpu)
+{
+	void **input_arg;
+	void *input_pg;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	input_pg = *input_arg;
+	*input_arg = NULL;
+	local_irq_restore(flags);
+	free_page((unsigned long)input_pg);
+
+	return 0;
+}
+
 /*
  * Functions for allocating and freeing memory with size and
  * alignment HV_HYP_PAGE_SIZE. These functions are needed because
@@ -140,6 +167,16 @@ static int __init hyperv_init(struct acpi_table_header *table)
 	pr_info("Hyper-V: Features 0x%x, hints 0x%x, misc 0x%x\n",
 		ms_hyperv.features, ms_hyperv.hints, ms_hyperv.misc_features);
 
+	/*
+	 * 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);
+
 	/*
 	 * If Hyper-V has crash notifications, set crash_kexec_post_notifiers
 	 * so that we will report the panic to Hyper-V before running kdump.
@@ -166,7 +203,7 @@ static int __init hyperv_init(struct acpi_table_header *table)
 		hv_vp_index[i] = VP_INVAL;
 
 	cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
-			"arm64/hyperv_init:online", hv_cpu_init, NULL);
+			"arm64/hyperv_init:online", hv_cpu_init, hv_cpu_die);
 	if (cpuhp < 0)
 		goto free_vp_index;
 

arch/arm64/include/asm/mshyperv.h

@@ -35,6 +35,8 @@ 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;
+
 /* Access various Hyper-V synthetic registers */
 static inline void hv_set_simp(u64 val)
 {

arch/x86/include/asm/mshyperv.h

@@ -184,38 +184,6 @@ 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>
 
@@ -184,6 +185,38 @@ static inline void hyperv_cleanup(void) {}
 #if IS_ENABLED(CONFIG_HYPERV)
 extern int hv_setup_stimer0_irq(int *irq, int *vector, void (*handler)(void));
 extern void hv_remove_stimer0_irq(int irq);
+
+/*
+ * 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;
+}
 #endif
 
 #endif