[RFC] xen/pvh: detect PVH after kexec

[Vitaly Kuznetsov <vkuznets@redhat.com>]

PVH guests after kexec boot like normal HVM guests and we're not entering
xen_prepare_pvh() but we still want to know that we're PVH. This hack does
the job by using XEN_IOPORT_MAGIC but I didn't find any straitforward way
to do it. Did I miss something? Or shall we introduce a CPUID leaf or
something like that?

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/xen/enlighten.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index ec1d5c4..4a30886 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -51,6 +51,7 @@
 #include <xen/hvm.h>
 #include <xen/hvc-console.h>
 #include <xen/acpi.h>
+#include <xen/platform_pci.h>
 
 #include <asm/paravirt.h>
 #include <asm/apic.h>
@@ -1765,6 +1766,20 @@ void __init xen_prepare_pvh(void)
 
 	x86_init.oem.arch_setup = xen_pvh_arch_setup;
 }
+
+static void xen_detect_pvh(void)
+{
+	short magic;
+
+	if (xen_pvh)
+		return;
+
+	magic = inw(XEN_IOPORT_MAGIC);
+	if (magic != XEN_IOPORT_MAGIC_VAL) {
+		xen_pvh = 1;
+		xen_pvh_arch_setup();
+	}
+}
 #endif
 
 void __ref xen_hvm_init_shared_info(void)
@@ -1912,6 +1927,9 @@ static void __init xen_hvm_guest_init(void)
 
 	init_hvm_pv_info();
 
+	/* Detect PVH booting after kexec */
+	xen_detect_pvh();
+
 	xen_hvm_init_shared_info();
 
 	xen_panic_handler_init();
-- 
2.9.3


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