[Xen-devel] [PATCH v3 1/5] x86/hyperv: setup hypercall page

[Wei Liu <wl@xen.org>]

Signed-off-by: Wei Liu <liuwe@microsoft.com>
---
v2:
1. Fix issue discovered by Michael
2. Use a statically allocated page as hypercall page
---
 xen/arch/x86/guest/hyperv/Makefile         |  1 +
 xen/arch/x86/guest/hyperv/hypercall_page.S | 21 +++++++++++++++++
 xen/arch/x86/guest/hyperv/hyperv.c         | 27 +++++++++++++++++++---
 3 files changed, 46 insertions(+), 3 deletions(-)
 create mode 100644 xen/arch/x86/guest/hyperv/hypercall_page.S

diff --git a/xen/arch/x86/guest/hyperv/Makefile b/xen/arch/x86/guest/hyperv/Makefile
index 68170109a9..1a8887d2f4 100644
--- a/xen/arch/x86/guest/hyperv/Makefile
+++ b/xen/arch/x86/guest/hyperv/Makefile
@@ -1 +1,2 @@
+obj-y += hypercall_page.o
 obj-y += hyperv.o
diff --git a/xen/arch/x86/guest/hyperv/hypercall_page.S b/xen/arch/x86/guest/hyperv/hypercall_page.S
new file mode 100644
index 0000000000..6d6ab913be
--- /dev/null
+++ b/xen/arch/x86/guest/hyperv/hypercall_page.S
@@ -0,0 +1,21 @@
+#include <asm/asm_defns.h>
+#include <asm/page.h>
+
+        .section ".text.page_aligned", "ax", @progbits
+        .p2align PAGE_SHIFT
+GLOBAL(hv_hypercall_page)
+        /* Return -1 for "not yet ready" state */
+        mov -1, %rax
+        ret
+1:
+        /* Fill the rest with `ret` */
+        .fill PAGE_SIZE - (1b - hv_hypercall_page), 1, 0xc3
+        .type hv_hypercall_page, STT_OBJECT
+        .size hv_hypercall_page, PAGE_SIZE
+
+/*
+ * Local variables:
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/x86/guest/hyperv/hyperv.c b/xen/arch/x86/guest/hyperv/hyperv.c
index 8d38313d7a..381be2a68c 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -19,16 +19,16 @@
  * Copyright (c) 2019 Microsoft.
  */
 #include <xen/init.h>
+#include <xen/domain_page.h>
 
 #include <asm/guest.h>
 #include <asm/guest/hyperv-tlfs.h>
 
 struct ms_hyperv_info __read_mostly ms_hyperv;
 
-static const struct hypervisor_ops ops = {
-    .name = "Hyper-V",
-};
+extern char hv_hypercall_page[];
 
+static const struct hypervisor_ops ops;
 const struct hypervisor_ops *__init hyperv_probe(void)
 {
     uint32_t eax, ebx, ecx, edx;
@@ -72,6 +72,27 @@ const struct hypervisor_ops *__init hyperv_probe(void)
     return &ops;
 }
 
+static void __init setup_hypercall_page(void)
+{
+    union hv_x64_msr_hypercall_contents hypercall_msr;
+
+    rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+    hypercall_msr.enable = 1;
+    hypercall_msr.guest_physical_address =
+        __pa(hv_hypercall_page) >> HV_HYP_PAGE_SHIFT;
+    wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+}
+
+static void __init setup(void)
+{
+    setup_hypercall_page();
+}
+
+static const struct hypervisor_ops ops = {
+    .name = "Hyper-V",
+    .setup = setup,
+};
+
 /*
  * Local variables:
  * mode: C
-- 
2.20.1


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