Subject: [PATCH v5 2/8] arm64: hyperv: Add hypercall and register access functions

From: Michael Kelley <[email-masked]>
Date: Thu, 3 Oct 2019 19:03:19 +0000

Add ARM64-specific code to make Hyper-V hypercalls and to
access virtual processor synthetic registers via hypercalls.
Hypercalls use a Hyper-V specific calling sequence with a non-zero
immediate value per Section 2.9 of the SMC Calling Convention
spec.

This code is architecture dependent and is mostly driven by
architecture independent code in the VMbus driver and the
Hyper-V timer clocksource driver.

This code is built only when CONFIG_HYPERV is enabled.

Signed-off-by: Michael Kelley <[email-masked]>
---
 MAINTAINERS                 |   1 +
 arch/arm64/Kbuild           |   1 +
 arch/arm64/hyperv/Makefile  |   2 +
 arch/arm64/hyperv/hv_hvc.S  |  44 +++++++++++++++
 arch/arm64/hyperv/hv_init.c | 133 ++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 181 insertions(+)
 create mode 100644 arch/arm64/hyperv/Makefile
 create mode 100644 arch/arm64/hyperv/hv_hvc.S
 create mode 100644 arch/arm64/hyperv/hv_init.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d464067..84f76f9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7566,6 +7566,7 @@ F:	arch/x86/kernel/cpu/mshyperv.c
 F:	arch/x86/hyperv
 F:	arch/arm64/include/asm/hyperv-tlfs.h
 F:	arch/arm64/include/asm/mshyperv.h
+F:	arch/arm64/hyperv
 F:	drivers/clocksource/hyperv_timer.c
 F:	drivers/hid/hid-hyperv.c
 F:	drivers/hv/
diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild
index d646582..2469421 100644
--- a/arch/arm64/Kbuild
+++ b/arch/arm64/Kbuild
@@ -3,4 +3,5 @@ obj-y			+= kernel/ mm/
 obj-$(CONFIG_NET)	+= net/
 obj-$(CONFIG_KVM)	+= kvm/
 obj-$(CONFIG_XEN)	+= xen/
+obj-$(CONFIG_HYPERV)	+= hyperv/
 obj-$(CONFIG_CRYPTO)	+= crypto/
diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
new file mode 100644
index 0000000..6bd8439
--- /dev/null
+++ b/arch/arm64/hyperv/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-y		:= hv_init.o hv_hvc.o
diff --git a/arch/arm64/hyperv/hv_hvc.S b/arch/arm64/hyperv/hv_hvc.S
new file mode 100644
index 0000000..09324ac
--- /dev/null
+++ b/arch/arm64/hyperv/hv_hvc.S
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Microsoft Hyper-V hypervisor invocation routines
+ *
+ * Copyright (C) 2018, Microsoft, Inc.
+ *
+ * Author : Michael Kelley <[email-masked]>
+ */
+
+#include <linux/linkage.h>
+
+	.text
+/*
+ * Do the HVC instruction.  For Hyper-V the argument is always 1.
+ * x0 contains the hypercall control value, while additional registers
+ * vary depending on the hypercall, and whether the hypercall arguments
+ * are in memory or in registers (a "fast" hypercall per the Hyper-V
+ * TLFS).  When the arguments are in memory x1 is the guest physical
+ * address of the input arguments, and x2 is the guest physical
+ * address of the output arguments.  When the arguments are in
+ * registers, the register values depends on the hypercall.  Note
+ * that this version cannot return any values in registers.
+ */
+ENTRY(hv_do_hvc)
+	hvc #1
+	ret
+ENDPROC(hv_do_hvc)
+
+/*
+ * This variant of HVC invocation is for hv_get_vpreg and
+ * hv_get_vpreg_128. The input parameters are passed in registers
+ * along with a pointer in x4 to where the output result should
+ * be stored. The output is returned in x15 and x16.  x18 is used as
+ * scratch space to avoid buildng a stack frame, as Hyper-V does
+ * not preserve registers x0-x17.
+ */
+ENTRY(hv_do_hvc_fast_get)
+	mov x18, x4
+	hvc #1
+	str x15,[x18]
+	str x16,[x18,#8]
+	ret
+ENDPROC(hv_do_hvc_fast_get)
diff --git a/arch/arm64/hyperv/hv_init.c b/arch/arm64/hyperv/hv_init.c
new file mode 100644
index 0000000..6808bc8
--- /dev/null
+++ b/arch/arm64/hyperv/hv_init.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Initialization of the interface with Microsoft's Hyper-V hypervisor,
+ * and various low level utility routines for interacting with Hyper-V.
+ *
+ * Copyright (C) 2019, Microsoft, Inc.
+ *
+ * Author : Michael Kelley <[email-masked]>
+ */
+
+
+#include <linux/types.h>
+#include <linux/version.h>
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/hyperv.h>
+#include <asm-generic/bug.h>
+#include <asm/hyperv-tlfs.h>
+#include <asm/mshyperv.h>
+
+/*
+ * hv_do_hypercall- Invoke the specified hypercall
+ */
+u64 hv_do_hypercall(u64 control, void *input, void *output)
+{
+	u64 input_address;
+	u64 output_address;
+
+	input_address = input ? virt_to_phys(input) : 0;
+	output_address = output ? virt_to_phys(output) : 0;
+	return hv_do_hvc(control, input_address, output_address);
+}
+EXPORT_SYMBOL_GPL(hv_do_hypercall);
+
+/*
+ * hv_do_fast_hypercall8 -- Invoke the specified hypercall
+ * with arguments in registers instead of physical memory.
+ * Avoids the overhead of virt_to_phys for simple hypercalls.
+ */
+
+u64 hv_do_fast_hypercall8(u16 code, u64 input)
+{
+	u64 control;
+
+	control = (u64)code | HV_HYPERCALL_FAST_BIT;
+	return hv_do_hvc(control, input);
+}
+EXPORT_SYMBOL_GPL(hv_do_fast_hypercall8);
+
+
+/*
+ * Set a single VP register to a 64-bit value.
+ */
+void hv_set_vpreg(u32 msr, u64 value)
+{
+	union hv_hypercall_status status;
+
+	status.as_uint64 = hv_do_hvc(
+		HVCALL_SET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
+			HV_HYPERCALL_REP_COUNT_1,
+		HV_PARTITION_ID_SELF,
+		HV_VP_INDEX_SELF,
+		msr,
+		0,
+		value,
+		0);
+
+	/*
+	 * Something is fundamentally broken in the hypervisor if
+	 * setting a VP register fails. There's really no way to
+	 * continue as a guest VM, so panic.
+	 */
+	BUG_ON(status.status != HV_STATUS_SUCCESS);
+}
+EXPORT_SYMBOL_GPL(hv_set_vpreg);
+
+
+/*
+ * Get the value of a single VP register, and only the low order 64 bits.
+ */
+u64 hv_get_vpreg(u32 msr)
+{
+	union hv_hypercall_status status;
+	struct hv_get_vp_register_output output;
+
+	status.as_uint64 = hv_do_hvc_fast_get(
+		HVCALL_GET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
+			HV_HYPERCALL_REP_COUNT_1,
+		HV_PARTITION_ID_SELF,
+		HV_VP_INDEX_SELF,
+		msr,
+		&output);
+
+	/*
+	 * Something is fundamentally broken in the hypervisor if
+	 * getting a VP register fails. There's really no way to
+	 * continue as a guest VM, so panic.
+	 */
+	BUG_ON(status.status != HV_STATUS_SUCCESS);
+
+	return output.registervaluelow;
+}
+EXPORT_SYMBOL_GPL(hv_get_vpreg);
+
+/*
+ * Get the value of a single VP register that is 128 bits in size.  This is a
+ * separate call in order to avoid complicating the calling sequence for
+ * the much more frequently used 64-bit version.
+ */
+void hv_get_vpreg_128(u32 msr, struct hv_get_vp_register_output *result)
+{
+	union hv_hypercall_status status;
+
+	status.as_uint64 = hv_do_hvc_fast_get(
+		HVCALL_GET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
+			HV_HYPERCALL_REP_COUNT_1,
+		HV_PARTITION_ID_SELF,
+		HV_VP_INDEX_SELF,
+		msr,
+		result);
+
+	/*
+	 * Something is fundamentally broken in the hypervisor if
+	 * getting a VP register fails. There's really no way to
+	 * continue as a guest VM, so panic.
+	 */
+	BUG_ON(status.status != HV_STATUS_SUCCESS);
+
+	return;
+
+}
+EXPORT_SYMBOL_GPL(hv_get_vpreg_128);
-- 
1.8.3.1

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