Re: [PATCH v5 4/4] x86/xen: Add "nopv" support for HVM guest

From: Zhenzhong Duan
Date: Mon Jul 08 2019 - 04:34:01 EST

On 2019/7/5 21:06, Boris Ostrovsky wrote:
On 7/2/19 9:19 PM, Zhenzhong Duan wrote:
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 1756cf7..09a010a 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -231,11 +231,37 @@ bool __init xen_hvm_need_lapic(void)
return true;
+static __init void xen_hvm_nopv_guest_late_init(void)
+ if (x86_platform.legacy.rtc || !x86_platform.legacy.no_vga)
+ return;
+ /* PVH detected. */
+ xen_pvh = true;
+ panic("\"nopv\" and \"xen_nopv\" parameters are unsupported in PVH guest.");
Can't all of this be done in xen_hvm_guest_late_init()? It has the same
tests already and it seems to me you should be able to panic from there.

Indeed, I didn't realize this, thanks for pointing, I'll fix it.