x86/hyperv: provide percpu hypercall input page

Hyper-V's input / output argument must be 8 bytes aligned an not cross
page boundary. One 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@microsoft.com>
Reviewed-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/guest/hyperv/hyperv.c

@@ -26,7 +26,10 @@
 #include <asm/guest/hyperv-tlfs.h>
 #include <asm/processor.h>
 
+#include "private.h"
+
 struct ms_hyperv_info __read_mostly ms_hyperv;
+DEFINE_PER_CPU_READ_MOSTLY(void *, hv_input_page);
 
 static uint64_t generate_guest_id(void)
 {
@@ -116,11 +119,35 @@ static void __init setup_hypercall_page(void)
     set_fixmap_x(FIX_X_HYPERV_HCALL, mfn << PAGE_SHIFT);
 }
 
+static int setup_hypercall_pcpu_arg(void)
+{
+    if ( this_cpu(hv_input_page) )
+        return 0;
+
+    this_cpu(hv_input_page) = alloc_xenheap_page();
+    if ( !this_cpu(hv_input_page) )
+    {
+        printk("CPU%u: Failed to allocate hypercall input page\n",
+               smp_processor_id());
+        return -ENOMEM;
+    }
+
+    return 0;
+}
+
 static void __init setup(void)
 {
     ASM_CONSTANT(HV_HCALL_PAGE, __fix_x_to_virt(FIX_X_HYPERV_HCALL));
 
     setup_hypercall_page();
+
+    if ( setup_hypercall_pcpu_arg() )
+        panic("Hyper-V hypercall percpu arg setup failed\n");
+}
+
+static int ap_setup(void)
+{
+    return setup_hypercall_pcpu_arg();
 }
 
 static void __init e820_fixup(struct e820map *e820)
@@ -134,6 +161,7 @@ static void __init e820_fixup(struct e820map *e820)
 static const struct hypervisor_ops ops = {
     .name = "Hyper-V",
     .setup = setup,
+    .ap_setup = ap_setup,
     .e820_fixup = e820_fixup,
 };
 

xen/arch/x86/guest/hyperv/private.h

@@ -0,0 +1,29 @@
+/******************************************************************************
+ * arch/x86/guest/hyperv/private.h
+ *
+ * Definitions / declarations only useful to Hyper-V code.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (c) 2020 Microsoft.
+ */
+
+#ifndef __XEN_HYPERV_PRIVIATE_H__
+#define __XEN_HYPERV_PRIVIATE_H__
+
+#include <xen/percpu.h>
+
+DECLARE_PER_CPU(void *, hv_input_page);
+
+#endif /* __XEN_HYPERV_PRIVIATE_H__  */