[PATCH v4 4/5] x86/xen: Add 'nopv' support for HVM guest

[Zhenzhong Duan]

PVH guest needs PV extentions to work, so 'nopv' parameter should be
ignored for PVH but not for HVM guest.

If PVH guest boots up via the Xen-PVH boot entry, xen_pvh is set early,
we know it's PVH guest and ignore 'nopv' parameter directly.

If PVH guest boots up via the normal boot entry same as HVM guest, it's
hard to distinguish PVH and HVM guest at that time.

To handle that case, add a new function xen_hvm_nopv_guest_late_init()
to detect PVH at a late time and panic itself if 'nopv' enabled for a
PVH guest.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
---
 arch/x86/xen/enlighten_hvm.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index 7fcb4ea..340dff8 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -25,6 +25,7 @@
 #include "mmu.h"
 #include "smp.h"
 
+extern bool nopv;
 static unsigned long shared_info_pfn;
 
 void xen_hvm_init_shared_info(void)
@@ -221,11 +222,36 @@ bool __init xen_hvm_need_lapic(void)
 	return true;
 }
 
+static __init void xen_hvm_nopv_guest_late_init(void)
+{
+#ifdef CONFIG_XEN_PVH
+	if (x86_platform.legacy.rtc || !x86_platform.legacy.no_vga)
+		return;
+
+	/* PVH detected. */
+	xen_pvh = true;
+
+	panic("nopv parameter isn't supported in PVH guest.");
+#endif
+}
+
+
 static uint32_t __init xen_platform_hvm(void)
 {
 	if (xen_pv_domain())
 		return 0;
 
+	if (xen_pvh_domain() && nopv) {
+		/* Guest booting via the Xen-PVH boot entry goes here */
+		pr_info("nopv parameter is ignored in PVH guest\n");
+	} else if (nopv) {
+		/*
+		 * Guest booting via normal boot entry (like via grub2) goes
+		 * here.
+		 */
+		x86_init.hyper.guest_late_init = xen_hvm_nopv_guest_late_init;
+		return 0;
+	}
 	return xen_cpuid_base();
 }
 
@@ -258,4 +284,5 @@ static __init void xen_hvm_guest_late_init(void)
 	.init.init_mem_mapping	= xen_hvm_init_mem_mapping,
 	.init.guest_late_init	= xen_hvm_guest_late_init,
 	.runtime.pin_vcpu       = xen_pin_vcpu,
+	.ignore_nopv            = true,
 };
-- 
1.8.3.1