hvm/vidirian: Avoid printing page_to_mfn(NULL) on error paths

While working in the viridian code, I noticed that 4cb6c4f4941

"x86/hvm: Use get_page_from_gfn() instead of get_gfn()/put_gfn."

introduced two error paths where page_to_mfn(NULL) would be formatted and
presented as a bad MFN.  This provides junk in the warning rather than
something useful.

These two codepaths are fixed up to match their counterpart in
wrmsr_hypervisor_regs()

While auditing the other changes from 4cb6c4f4941, I noticed a small
optimisation which could be made by changing the order of the validity checks
to remove 6 NULL pointer checks.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index d5462f2aae..a6721c3eb0 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -157,7 +157,7 @@ static void enable_hypercall_page(struct domain *d)
         if ( page )
             put_page(page);
         gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
-                 page_to_mfn(page));
+                 page ? page_to_mfn(page) : INVALID_MFN);
         return;
     }
 
@@ -202,7 +202,7 @@ static void initialize_apic_assist(struct vcpu *v)
         if ( page )
             put_page(page);
         gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
-                 page_to_mfn(page));
+                 page ? page_to_mfn(page) : INVALID_MFN);
         return;
     }