[Xen-devel] [PATCH 6/8] x86/hyperv: provide percpu hypercall input page

[Wei Liu <wl@xen.org>]

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.

The page tracking structure is not bound to hypercall because it is a
common pattern for Xen to write guest physical address to Hyper-V while
at the same time accessing the page via a pointer.

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@microsoft.com>
---
 xen/arch/x86/guest/hyperv/hyperv.c | 26 ++++++++++++++++++++++++++
 xen/include/asm-x86/guest/hyperv.h |  8 ++++++++
 2 files changed, 34 insertions(+)

diff --git a/xen/arch/x86/guest/hyperv/hyperv.c b/xen/arch/x86/guest/hyperv/hyperv.c
index 438910c8cb..67667936e9 100644
--- a/xen/arch/x86/guest/hyperv/hyperv.c
+++ b/xen/arch/x86/guest/hyperv/hyperv.c
@@ -28,6 +28,7 @@ struct ms_hyperv_info __read_mostly ms_hyperv;
 
 void *hv_hypercall;
 static struct page_info *hv_hypercall_page;
+DEFINE_PER_CPU_READ_MOSTLY(struct hyperv_pcpu_page, hv_pcpu_input_arg);
 
 static const struct hypervisor_ops ops;
 const struct hypervisor_ops *__init hyperv_probe(void)
@@ -96,14 +97,39 @@ static void __init setup_hypercall_page(void)
     wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 }
 
+static void setup_hypercall_pcpu_arg(void)
+{
+    struct page_info *pg;
+    void *mapping;
+    unsigned int cpu = smp_processor_id();
+
+    pg = alloc_domheap_page(NULL, 0);
+    if ( !pg )
+        panic("Failed to setup hypercall input page for %u\n", cpu);
+
+    mapping = __map_domain_page_global(pg);
+    if ( !mapping )
+        panic("Failed to map hypercall input page for %u\n", cpu);
+
+    this_cpu(hv_pcpu_input_arg).maddr = page_to_maddr(pg);
+    this_cpu(hv_pcpu_input_arg).mapping = 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..83f297468f 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 +65,12 @@ struct ms_hyperv_info {
 };
 extern struct ms_hyperv_info ms_hyperv;
 
+struct hyperv_pcpu_page {
+    paddr_t maddr;
+    void *mapping;
+};
+DECLARE_PER_CPU(struct hyperv_pcpu_page, hv_pcpu_input_arg);
+
 const struct hypervisor_ops *hyperv_probe(void);
 
 #else
-- 
2.20.1


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