[Xen-devel] [PATCH 4/8] x86/hyperv: setup hypercall page

[Wei Liu <wl@xxxxxxx>]

Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
---
 xen/arch/x86/guest/hyperv/hyperv.c | 41 +++++++++++++++++++++++++++---
 1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
b/xen/arch/x86/guest/hyperv/hyperv.c
index c6a26c5453..438910c8cb 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -19,16 +19,17 @@
  * 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",
-};
+void *hv_hypercall;
+static struct page_info *hv_hypercall_page;
 
+static const struct hypervisor_ops ops;
 const struct hypervisor_ops *__init hyperv_probe(void)
 {
     uint32_t eax, ebx, ecx, edx;
@@ -71,6 +72,40 @@ 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;
+
+    /* Unfortunately there isn't a really good way to unwind Xen to
+     * not use Hyper-V hooks, so panic if anything goes wrong.
+     *
+     * In practice if page allocation fails this early on it is
+     * unlikely we can get a working system later.
+     */
+    hv_hypercall_page = alloc_domheap_page(NULL, 0);
+    if ( !hv_hypercall_page )
+        panic("Failed to allocate Hyper-V hypercall page\n");
+
+    hv_hypercall = __map_domain_page_global(hv_hypercall_page);
+    if ( !hv_hypercall )
+        panic("Failed to map Hyper-V hypercall page\n");
+
+    rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+    hypercall_msr.enable = 1;
+    hypercall_msr.guest_physical_address = page_to_maddr(hv_hypercall_page);
+    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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