[Xen-devel] [PATCH v2 10/18] xen: setup hypercall page for PVH

[Juergen Gross <jgross@xxxxxxxx>]

Add the needed code to setup the hypercall page for calling into the
Xen hypervisor.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 grub-core/kern/i386/xen/pvh.c | 70 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/grub-core/kern/i386/xen/pvh.c b/grub-core/kern/i386/xen/pvh.c
index 182ef95f9..c1b1cf8db 100644
--- a/grub-core/kern/i386/xen/pvh.c
+++ b/grub-core/kern/i386/xen/pvh.c
@@ -20,14 +20,84 @@
 #include <grub/misc.h>
 #include <grub/memory.h>
 #include <grub/mm.h>
+#include <grub/i386/cpuid.h>
 #include <grub/xen.h>
 #include <grub/machine/kernel.h>
 
 grub_uint64_t grub_rsdp_addr;
 
+static struct { char _entry[32]; } hypercall_page[128]
+  __attribute__ ((aligned (GRUB_XEN_PAGE_SIZE)));
+
+static grub_uint32_t xen_cpuid_base;
+
+static void
+grub_xen_early_halt (void)
+{
+  asm volatile ("hlt");
+}
+
+static void
+grub_xen_cpuid_base (void)
+{
+  grub_uint32_t base, eax, signature[3];
+
+  for (base = 0x40000000; base < 0x40010000; base += 0x100)
+    {
+      grub_cpuid (base, eax, signature[0], signature[1], signature[2]);
+      if (!grub_memcmp ("XenVMMXenVMM", signature, 12) && (eax - base) >= 2)
+       {
+         xen_cpuid_base = base;
+         return;
+       }
+    }
+
+  grub_xen_early_halt ();
+}
+
+static void
+grub_xen_setup_hypercall_page (void)
+{
+  grub_uint32_t msr, pfn, eax, ebx, ecx, edx;
+
+  grub_cpuid (xen_cpuid_base + 2, eax, ebx, ecx, edx);
+  msr = ebx;
+  pfn = (grub_uint32_t) (&hypercall_page[0]);
+
+  asm volatile ("wrmsr" : : "c" (msr), "a" (pfn), "d" (0) : "memory");
+}
+
+int
+grub_xen_hypercall (grub_uint32_t callno, grub_uint32_t a0,
+                   grub_uint32_t a1, grub_uint32_t a2,
+                   grub_uint32_t a3, grub_uint32_t a4,
+                   grub_uint32_t a5 __attribute__ ((unused)))
+{
+  register unsigned long __res  asm("eax");
+  register unsigned long __arg0 asm("ebx") = __arg0;
+  register unsigned long __arg1 asm("ecx") = __arg1;
+  register unsigned long __arg2 asm("edx") = __arg2;
+  register unsigned long __arg3 asm("esi") = __arg3;
+  register unsigned long __arg4 asm("edi") = __arg4;
+
+  __arg0 = a0;
+  __arg1 = a1;
+  __arg2 = a2;
+  __arg3 = a3;
+  __arg4 = a4;
+  asm volatile ("call *%[callno]"
+               : "=r" (__res), "+r" (__arg0), "+r" (__arg1), "+r" (__arg2),
+                 "+r" (__arg3), "+r" (__arg4)
+               : [callno] "a" (&hypercall_page[callno])
+               : "memory");
+  return __res;
+}
+
 void
 grub_xen_setup_pvh (void)
 {
+  grub_xen_cpuid_base ();
+  grub_xen_setup_hypercall_page ();
 }
 
 grub_err_t
-- 
2.16.4


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