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From:   Michael Kelley <mikelley@microsoft.com>
To:     kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com,
        wei.liu@kernel.org, tglx@linutronix.de, mingo@redhat.com,
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        linux-hyperv@vger.kernel.org, sunilmut@microsoft.com
Cc:     mikelley@microsoft.com
Subject: [PATCH 1/1] Drivers: hv: Move Hyper-V extended capability check to arch neutral code
Date:   Wed,  2 Jun 2021 14:36:44 -0700
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The extended capability query code is currently under arch/x86, but it
is architecture neutral, and is used by arch neutral code in the Hyper-V
balloon driver. Hence the balloon driver fails to build on other
architectures.

Fix by moving the ext cap code out from arch/x86.  Because it is also
called from built-in architecture specific code, it can't be in a module,
so the Makefile treats as built-in even when CONFIG_HYPERV is "m".  Also
drivers/Makefile is tweaked because this is the first occurrence of a
Hyper-V file that is built-in even when CONFIG_HYPERV is "m".

While here, update the hypercall status check to use the new helper
function instead of open coding. No functional change.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/hyperv/hv_init.c | 47 ---------------------------------
 drivers/Makefile          |  2 +-
 drivers/hv/Makefile       |  3 +++
 drivers/hv/hv_common.c    | 66 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 48 deletions(-)
 create mode 100644 drivers/hv/hv_common.c

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index bb0ae4b..6952e21 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -614,50 +614,3 @@ bool hv_is_isolation_supported(void)
 	return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
 }
 EXPORT_SYMBOL_GPL(hv_is_isolation_supported);
-
-/* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
-bool hv_query_ext_cap(u64 cap_query)
-{
-	/*
-	 * The address of the 'hv_extended_cap' variable will be used as an
-	 * output parameter to the hypercall below and so it should be
-	 * compatible with 'virt_to_phys'. Which means, it's address should be
-	 * directly mapped. Use 'static' to keep it compatible; stack variables
-	 * can be virtually mapped, making them imcompatible with
-	 * 'virt_to_phys'.
-	 * Hypercall input/output addresses should also be 8-byte aligned.
-	 */
-	static u64 hv_extended_cap __aligned(8);
-	static bool hv_extended_cap_queried;
-	u64 status;
-
-	/*
-	 * Querying extended capabilities is an extended hypercall. Check if the
-	 * partition supports extended hypercall, first.
-	 */
-	if (!(ms_hyperv.priv_high & HV_ENABLE_EXTENDED_HYPERCALLS))
-		return false;
-
-	/* Extended capabilities do not change at runtime. */
-	if (hv_extended_cap_queried)
-		return hv_extended_cap & cap_query;
-
-	status = hv_do_hypercall(HV_EXT_CALL_QUERY_CAPABILITIES, NULL,
-				 &hv_extended_cap);
-
-	/*
-	 * The query extended capabilities hypercall should not fail under
-	 * any normal circumstances. Avoid repeatedly making the hypercall, on
-	 * error.
-	 */
-	hv_extended_cap_queried = true;
-	status &= HV_HYPERCALL_RESULT_MASK;
-	if (status != HV_STATUS_SUCCESS) {
-		pr_err("Hyper-V: Extended query capabilities hypercall failed 0x%llx\n",
-		       status);
-		return false;
-	}
-
-	return hv_extended_cap & cap_query;
-}
-EXPORT_SYMBOL_GPL(hv_query_ext_cap);
diff --git a/drivers/Makefile b/drivers/Makefile
index 5a6d613..1c2e1ac 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -161,7 +161,7 @@ obj-$(CONFIG_SOUNDWIRE)		+= soundwire/
 
 # Virtualization drivers
 obj-$(CONFIG_VIRT_DRIVERS)	+= virt/
-obj-$(CONFIG_HYPERV)		+= hv/
+obj-$(subst m,y,$(CONFIG_HYPERV))	+= hv/
 
 obj-$(CONFIG_PM_DEVFREQ)	+= devfreq/
 obj-$(CONFIG_EXTCON)		+= extcon/
diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
index 94daf82..d76df5c 100644
--- a/drivers/hv/Makefile
+++ b/drivers/hv/Makefile
@@ -11,3 +11,6 @@ hv_vmbus-y := vmbus_drv.o \
 		 channel_mgmt.o ring_buffer.o hv_trace.o
 hv_vmbus-$(CONFIG_HYPERV_TESTING)	+= hv_debugfs.o
 hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_fcopy.o hv_utils_transport.o
+
+# Code that must be built-in
+obj-$(subst m,y,$(CONFIG_HYPERV)) += hv_common.o
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
new file mode 100644
index 0000000..f0053c7
--- /dev/null
+++ b/drivers/hv/hv_common.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Architecture neutral utility routines for interacting with
+ * Hyper-V. This file is specifically for code that must be
+ * built-in to the kernel image when CONFIG_HYPERV is set
+ * (vs. being in a module) because it is called from architecture
+ * specific code under arch/.
+ *
+ * Copyright (C) 2021, Microsoft, Inc.
+ *
+ * Author : Michael Kelley <mikelley@microsoft.com>
+ */
+
+#include <linux/types.h>
+#include <linux/export.h>
+#include <linux/bitfield.h>
+#include <asm/hyperv-tlfs.h>
+#include <asm/mshyperv.h>
+
+
+/* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
+bool hv_query_ext_cap(u64 cap_query)
+{
+	/*
+	 * The address of the 'hv_extended_cap' variable will be used as an
+	 * output parameter to the hypercall below and so it should be
+	 * compatible with 'virt_to_phys'. Which means, it's address should be
+	 * directly mapped. Use 'static' to keep it compatible; stack variables
+	 * can be virtually mapped, making them imcompatible with
+	 * 'virt_to_phys'.
+	 * Hypercall input/output addresses should also be 8-byte aligned.
+	 */
+	static u64 hv_extended_cap __aligned(8);
+	static bool hv_extended_cap_queried;
+	u64 status;
+
+	/*
+	 * Querying extended capabilities is an extended hypercall. Check if the
+	 * partition supports extended hypercall, first.
+	 */
+	if (!(ms_hyperv.priv_high & HV_ENABLE_EXTENDED_HYPERCALLS))
+		return false;
+
+	/* Extended capabilities do not change at runtime. */
+	if (hv_extended_cap_queried)
+		return hv_extended_cap & cap_query;
+
+	status = hv_do_hypercall(HV_EXT_CALL_QUERY_CAPABILITIES, NULL,
+				 &hv_extended_cap);
+
+	/*
+	 * The query extended capabilities hypercall should not fail under
+	 * any normal circumstances. Avoid repeatedly making the hypercall, on
+	 * error.
+	 */
+	hv_extended_cap_queried = true;
+	if (!hv_result_success(status)) {
+		pr_err("Hyper-V: Extended query capabilities hypercall failed 0x%llx\n",
+		       status);
+		return false;
+	}
+
+	return hv_extended_cap & cap_query;
+}
+EXPORT_SYMBOL_GPL(hv_query_ext_cap);
-- 
1.8.3.1