[PATCH char-misc v2 1/1] Drivers: hv: vmbus: Remove x86-isms from arch independent drivers

[mikelley@exchange.microsoft.com]

From: Michael Kelley <mikelley@microsoft.com>

hv_is_hypercall_page_setup() is used to check if Hyper-V is
initialized, but a 'hypercall page' is an x86 implementation detail
that isn't necessarily present on other architectures. Rename to the
architecture independent hv_is_hyperv_initialized() and add check
that x86_hyper is pointing to Hyper-V.  Use this function instead of
direct references to x86-specific data structures in vmbus_drv.c,
and remove now redundant call in hv_init(). Also remove 'x86' from
the string name passed to cpuhp_setup_state().

Signed-off-by: Michael Kelley <mikelley@microsoft.com>

---
Changed since v1:
* Incorporated x86_hyper check into hv_is_hyperv_initialized() per
  KY Srinivasan's comment that it is still needed
* Removed now redundant call to hv_is_hyperv_initialized() in hv_init()

---
 arch/x86/hyperv/hv_init.c       | 19 ++++++++++++-------
 arch/x86/include/asm/mshyperv.h |  4 ++--
 drivers/hv/hv.c                 |  3 ---
 drivers/hv/vmbus_drv.c          |  5 ++---
 4 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index aeb8edf..641ed26 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -239,17 +239,22 @@ void hyperv_report_panic(struct pt_regs *regs, long err)
 }
 EXPORT_SYMBOL_GPL(hyperv_report_panic);
 
-bool hv_is_hypercall_page_setup(void)
+bool hv_is_hyperv_initialized(void)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 
-	/* Check if the hypercall page is setup */
+	/* Ensure that we're really on Hyper-V, and not a KVM or Xen
+	 * emulation of Hyper-V
+	 */
+	if (x86_hyper != &x86_hyper_ms_hyperv)
+		return false;
+
+	/* Verify that earlier initialization succeeded by checking
+	 * that the hypercall page is setup
+	 */
 	hypercall_msr.as_uint64 = 0;
 	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 
-	if (!hypercall_msr.enable)
-		return false;
-
-	return true;
+	return hypercall_msr.enable;
 }
-EXPORT_SYMBOL_GPL(hv_is_hypercall_page_setup);
+EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index bd89104..740dc97 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -311,11 +311,11 @@ static inline int hv_cpu_number_to_vp_number(int cpu_number)
 void hyperv_setup_mmu_ops(void);
 void hyper_alloc_mmu(void);
 void hyperv_report_panic(struct pt_regs *regs, long err);
-bool hv_is_hypercall_page_setup(void);
+bool hv_is_hyperv_initialized(void);
 void hyperv_cleanup(void);
 #else /* CONFIG_HYPERV */
 static inline void hyperv_init(void) {}
-static inline bool hv_is_hypercall_page_setup(void) { return false; }
+static inline bool hv_is_hyperv_initialized(void) { return false; }
 static inline void hyperv_cleanup(void) {}
 static inline void hyperv_setup_mmu_ops(void) {}
 #endif /* CONFIG_HYPERV */
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 8267439..fe96aab 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -49,9 +49,6 @@ struct hv_context hv_context = {
  */
 int hv_init(void)
 {
-	if (!hv_is_hypercall_page_setup())
-		return -ENOTSUPP;
-
 	hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
 	if (!hv_context.cpu_context)
 		return -ENOMEM;
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 8fe13cd..574668c 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -37,7 +37,6 @@
 #include <linux/sched/task_stack.h>
 
 #include <asm/hyperv.h>
-#include <asm/hypervisor.h>
 #include <asm/mshyperv.h>
 #include <linux/notifier.h>
 #include <linux/ptrace.h>
@@ -1049,7 +1048,7 @@ static int vmbus_bus_init(void)
 	 * Initialize the per-cpu interrupt state and
 	 * connect to the host.
 	 */
-	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv:online",
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
 				hv_synic_init, hv_synic_cleanup);
 	if (ret < 0)
 		goto err_alloc;
@@ -1711,7 +1710,7 @@ static int __init hv_acpi_init(void)
 {
 	int ret, t;
 
-	if (x86_hyper != &x86_hyper_ms_hyperv)
+	if (!hv_is_hyperv_initialized())
 		return -ENODEV;
 
 	init_completion(&probe_event);
-- 
1.8.3.1