[Xen-devel] [PATCH 8/8] x86/hyperv: setup VP assist page

[Wei Liu <wl@xxxxxxx>]

VP assist page is rather important as we need to toggle some bits in
that page such that L1 guest can make hypercalls directly to L0 Hyper-V.

Preemptively split out set_vp_assist page which will be used in the resume
path.

Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
---
 xen/arch/x86/guest/hyperv/hyperv.c | 35 ++++++++++++++++++++++++++++++
 xen/include/asm-x86/guest/hyperv.h |  1 +
 2 files changed, 36 insertions(+)

diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
b/xen/arch/x86/guest/hyperv/hyperv.c
index da3a8cd85d..a88b9ae6d9 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -30,6 +30,7 @@ void *hv_hypercall;
 static struct page_info *hv_hypercall_page;
 DEFINE_PER_CPU_READ_MOSTLY(struct hyperv_pcpu_page, hv_pcpu_input_arg);
 DEFINE_PER_CPU_READ_MOSTLY(unsigned int, hv_vp_index);
+DEFINE_PER_CPU_READ_MOSTLY(struct hyperv_pcpu_page, hv_vp_assist);
 
 static const struct hypervisor_ops ops;
 const struct hypervisor_ops *__init hyperv_probe(void)
@@ -125,17 +126,51 @@ static void setup_vp_index(void)
     this_cpu(hv_vp_index) = vp_index_msr;
 }
 
+static void set_vp_assist(void)
+{
+    uint64_t val = paddr_to_pfn(this_cpu(hv_vp_assist).maddr);
+
+    val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) |
+        HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;
+
+    wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
+}
+
+static void setup_vp_assist(void)
+{
+    struct page_info *pg;
+    void *mapping;
+    unsigned int cpu = smp_processor_id();
+
+    pg = alloc_domheap_page(NULL, 0);
+    if ( !pg )
+        panic("Failed to allocate vp_assist page for %u\n", cpu);
+
+    mapping = __map_domain_page_global(pg);
+    if ( !mapping )
+        panic("Failed to map vp_assist page for %u\n", cpu);
+
+    clear_page(mapping);
+
+    this_cpu(hv_vp_assist).maddr = page_to_maddr(pg);
+    this_cpu(hv_vp_assist).mapping = mapping;
+
+    set_vp_assist();
+}
+
 static void __init setup(void)
 {
     setup_hypercall_page();
     setup_hypercall_pcpu_arg();
     setup_vp_index();
+    setup_vp_assist();
 }
 
 static void ap_setup(void)
 {
     setup_hypercall_pcpu_arg();
     setup_vp_index();
+    setup_vp_assist();
 }
 
 static const struct hypervisor_ops ops = {
diff --git a/xen/include/asm-x86/guest/hyperv.h 
b/xen/include/asm-x86/guest/hyperv.h
index 4b635829f3..917f4e02c2 100644
--- a/xen/include/asm-x86/guest/hyperv.h
+++ b/xen/include/asm-x86/guest/hyperv.h
@@ -71,6 +71,7 @@ struct hyperv_pcpu_page {
 };
 DECLARE_PER_CPU(struct hyperv_pcpu_page, hv_pcpu_input_arg);
 DECLARE_PER_CPU(unsigned int, hv_vp_index);
+DECLARE_PER_CPU(struct hyperv_pcpu_page, hv_vp_assist);
 
 const struct hypervisor_ops *hyperv_probe(void);
 
-- 
2.20.1


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