[Xen-devel] [PATCH v4 7/7] x86/hyperv: setup VP assist page

[Wei Liu <wl@xxxxxxx>]

VP assist page is rather important as we need to toggle some bits in it
for efficient nested virtualisation.

Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
---
v4:
1. Use private.h
2. Prevent leak

v3:
1. Use xenheap page
2. Drop set_vp_assist

v2:
1. Use HV_HYP_PAGE_SHIFT instead
---
 xen/arch/x86/guest/hyperv/hyperv.c  | 26 ++++++++++++++++++++++++++
 xen/arch/x86/guest/hyperv/private.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
b/xen/arch/x86/guest/hyperv/hyperv.c
index 085e646dc6..89a8f316b2 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -32,6 +32,7 @@
 struct ms_hyperv_info __read_mostly ms_hyperv;
 DEFINE_PER_CPU_READ_MOSTLY(void *, hv_pcpu_input_arg);
 DEFINE_PER_CPU_READ_MOSTLY(unsigned int, hv_vp_index);
+DEFINE_PER_CPU_READ_MOSTLY(void *, hv_vp_assist);
 
 static uint64_t generate_guest_id(void)
 {
@@ -142,15 +143,40 @@ static void setup_hypercall_pcpu_arg(void)
     this_cpu(hv_vp_index) = vp_index_msr;
 }
 
+static void setup_vp_assist(void)
+{
+    void *mapping;
+    uint64_t val;
+
+    mapping = this_cpu(hv_vp_assist);
+
+    if ( !mapping )
+    {
+        mapping = alloc_xenheap_page();
+        if ( !mapping )
+            panic("Failed to allocate vp_assist page for CPU%u\n",
+                  smp_processor_id());
+
+        clear_page(mapping);
+        this_cpu(hv_vp_assist) = mapping;
+    }
+
+    val = (virt_to_mfn(mapping) << HV_HYP_PAGE_SHIFT)
+        | HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;
+    wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
+}
+
 static void __init setup(void)
 {
     setup_hypercall_page();
     setup_hypercall_pcpu_arg();
+    setup_vp_assist();
 }
 
 static void ap_setup(void)
 {
     setup_hypercall_pcpu_arg();
+    setup_vp_assist();
 }
 
 static const struct hypervisor_ops ops = {
diff --git a/xen/arch/x86/guest/hyperv/private.h 
b/xen/arch/x86/guest/hyperv/private.h
index da70990401..af419e9d4b 100644
--- a/xen/arch/x86/guest/hyperv/private.h
+++ b/xen/arch/x86/guest/hyperv/private.h
@@ -26,5 +26,6 @@
 
 DECLARE_PER_CPU(void *, hv_pcpu_input_arg);
 DECLARE_PER_CPU(unsigned int, hv_vp_index);
+DECLARE_PER_CPU(void *, hv_vp_assist);
 
 #endif /* __XEN_HYPERV_PRIVIATE_H__  */
-- 
2.20.1


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