[PATCH] vVMX: adjust VMPTRLD error handling

[Jan Beulich]

There are two issues there: When hvm_map_guest_frame_rw() yields a r/o
page mapping, we fail to indicate the failure to the guest, and we fall
over the NULL pointer in nvcpu->nv_vvmcx when subsequently invoking
nvmx_set_vmcs_pointer() (if no earlier VMPTRLD put in place a valid
value).

Fixes: 5dbbaa0fe121 ("x86/vvmx: fix I/O and MSR bitmaps mapping")
Reported-by: Manuel Andreas <manuel.andr...@tum.de>
Signed-off-by: Jan Beulich <jbeul...@suse.com>

--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1820,7 +1820,7 @@ static int nvmx_handle_vmptrld(struct cp
                 vvmcx = NULL;
             }
         }
-        else
+        if ( !vvmcx )
         {
             vmfail(regs, VMX_INSN_VMPTRLD_INVALID_PHYADDR);
             goto out;