[Xen-devel] [PATCH v3 3/5] x86/hyperv: provide percpu hypercall input page

[Wei Liu <wl@xxxxxxx>]

Hyper-V's input / output argument must be 8 bytes aligned an not cross
page boundary. The easiest way to satisfy those requirements is to use
percpu page.

For the foreseeable future we only need to provide input for TLB
and APIC hypercalls, so skip setting up an output page.

We will also need to provide an ap_setup hook for secondary cpus to
setup its own input page.

Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
---
v3:
1. Use xenheap page instead
2. Drop page tracking structure
3. Drop Paul's review tag
---
 xen/arch/x86/guest/hyperv/hyperv.c | 20 ++++++++++++++++++++
 xen/include/asm-x86/guest/hyperv.h |  4 ++++
 2 files changed, 24 insertions(+)

diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
b/xen/arch/x86/guest/hyperv/hyperv.c
index 381be2a68c..7e046dfc04 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -27,6 +27,7 @@
 struct ms_hyperv_info __read_mostly ms_hyperv;
 
 extern char hv_hypercall_page[];
+DEFINE_PER_CPU_READ_MOSTLY(void *, hv_pcpu_input_arg);
 
 static const struct hypervisor_ops ops;
 const struct hypervisor_ops *__init hyperv_probe(void)
@@ -83,14 +84,33 @@ static void __init setup_hypercall_page(void)
     wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 }
 
+static void setup_hypercall_pcpu_arg(void)
+{
+    void *mapping;
+
+    mapping = alloc_xenheap_page();
+    if ( !mapping )
+        panic("Failed to allocate hypercall input page for %u\n",
+              smp_processor_id());
+
+    this_cpu(hv_pcpu_input_arg) = mapping;
+}
+
 static void __init setup(void)
 {
     setup_hypercall_page();
+    setup_hypercall_pcpu_arg();
+}
+
+static void ap_setup(void)
+{
+    setup_hypercall_pcpu_arg();
 }
 
 static const struct hypervisor_ops ops = {
     .name = "Hyper-V",
     .setup = setup,
+    .ap_setup = ap_setup,
 };
 
 /*
diff --git a/xen/include/asm-x86/guest/hyperv.h 
b/xen/include/asm-x86/guest/hyperv.h
index c7a7f32bd5..6cf2eab62f 100644
--- a/xen/include/asm-x86/guest/hyperv.h
+++ b/xen/include/asm-x86/guest/hyperv.h
@@ -51,6 +51,8 @@ static inline uint64_t hv_scale_tsc(uint64_t tsc, uint64_t 
scale,
 
 #ifdef CONFIG_HYPERV_GUEST
 
+#include <xen/percpu.h>
+
 #include <asm/guest/hypervisor.h>
 
 struct ms_hyperv_info {
@@ -63,6 +65,8 @@ struct ms_hyperv_info {
 };
 extern struct ms_hyperv_info ms_hyperv;
 
+DECLARE_PER_CPU(void *, hv_pcpu_input_arg);
+
 const struct hypervisor_ops *hyperv_probe(void);
 
 #else
-- 
2.20.1


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