xen/pvh: Move Xen specific PVH VM initialization out of common file

We need to refactor PVH entry code so that support for other hypervisors
like Qemu/KVM can be added more easily.

This patch moves the small block of code used for initializing Xen PVH
virtual machines into the Xen specific file. This initialization is not
going to be needed for Qemu/KVM guests. Moving it out of the common file
is going to allow us to compile kernels in the future without CONFIG_XEN
that are still capable of being booted as a Qemu/KVM guest via the PVH
entry point.

Signed-off-by: Maran Wilson <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>

arch/x86/platform/pvh/enlighten.c

@@ -81,27 +81,38 @@ static void __init init_pvh_bootparams(void)
 	x86_init.acpi.get_root_pointer = pvh_get_root_pointer;
 }
 
+/*
+ * If we are trying to boot a Xen PVH guest, it is expected that the kernel
+ * will have been configured to provide the required override for this routine.
+ */
+void __init __weak xen_pvh_init(void)
+{
+	xen_raw_printk("Error: Missing xen PVH initialization\n");
+	BUG();
+}
+
+/*
+ * When we add support for other hypervisors like Qemu/KVM, this routine can
+ * selectively invoke the appropriate initialization based on guest type.
+ */
+static void hypervisor_specific_init(void)
+{
+	xen_pvh_init();
+}
+
 /*
  * This routine (and those that it might call) should not use
  * anything that lives in .bss since that segment will be cleared later.
  */
 void __init xen_prepare_pvh(void)
 {
-	u32 msr;
-	u64 pfn;
-
 	if (pvh_start_info.magic != XEN_HVM_START_MAGIC_VALUE) {
 		xen_raw_printk("Error: Unexpected magic value (0x%08x)\n",
 				pvh_start_info.magic);
 		BUG();
 	}
 
-	xen_pvh = 1;
-	xen_start_flags = pvh_start_info.flags;
-
-	msr = cpuid_ebx(xen_cpuid_base() + 2);
-	pfn = __pa(hypercall_page);
-	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
+	hypervisor_specific_init();
 
 	init_pvh_bootparams();
 }

arch/x86/xen/enlighten_pvh.c

@@ -1,5 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <linux/types.h>
+#include <linux/acpi.h>
+
+#include <asm/io_apic.h>
+#include <asm/hypervisor.h>
+
+#include <xen/xen.h>
+#include <asm/xen/interface.h>
+#include <asm/xen/hypercall.h>
 
 /*
  * PVH variables.
@@ -8,3 +15,16 @@
  * after startup_{32|64} is invoked, which will clear the .bss segment.
  */
 bool xen_pvh __attribute__((section(".data"))) = 0;
+
+void __init xen_pvh_init(void)
+{
+	u32 msr;
+	u64 pfn;
+
+	xen_pvh = 1;
+	xen_start_flags = pvh_start_info.flags;
+
+	msr = cpuid_ebx(xen_cpuid_base() + 2);
+	pfn = __pa(hypercall_page);
+	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
+}

include/xen/xen.h

@@ -29,6 +29,9 @@ extern bool xen_pvh;
 
 extern uint32_t xen_start_flags;
 
+#include <xen/interface/hvm/start_info.h>
+extern struct hvm_start_info pvh_start_info;
+
 #ifdef CONFIG_XEN_DOM0
 #include <xen/interface/xen.h>
 #include <asm/xen/hypervisor.h>