>From 841a6950fec5b43b370653e0c833a54fed64882e Mon Sep 17 00:00:00 2001
From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Date: Wed, 9 Dec 2020 12:50:38 +0000
Subject: extable-dbg


diff --git a/xen/arch/x86/extable.c b/xen/arch/x86/extable.c
index 70972f1085..88b05bef38 100644
--- a/xen/arch/x86/extable.c
+++ b/xen/arch/x86/extable.c
@@ -191,6 +191,10 @@ static int __init stub_selftest(void)
 __initcall(stub_selftest);
 #endif
 
+#include <xen/sched.h>
+#include <xen/softirq.h>
+const char *vec_name(unsigned int vec);
+
 unsigned long
 search_pre_exception_table(struct cpu_user_regs *regs)
 {
@@ -199,7 +203,21 @@ search_pre_exception_table(struct cpu_user_regs *regs)
         __start___pre_ex_table, __stop___pre_ex_table-1, addr);
     if ( fixup )
     {
-        dprintk(XENLOG_INFO, "Pre-exception: %p -> %p\n", _p(addr), _p(fixup));
+        static int count;
+
+        printk(XENLOG_ERR "IRET fault: %s[%04x]\n",
+               vec_name(regs->entry_vector), regs->error_code);
+
+        if ( regs->entry_vector == X86_EXC_PF )
+            printk(XENLOG_ERR "%%cr2 %016lx\n", read_cr2());
+
+        if ( count++ > 2 )
+        {
+            domain_crash(current->domain);
+            for ( ;; )
+                do_softirq();
+        }
+
         perfc_incr(exception_fixed);
     }
     return fixup;
diff --git a/xen/arch/x86/pv/descriptor-tables.c b/xen/arch/x86/pv/descriptor-tables.c
index 39c1a2311a..6bc58bba67 100644
--- a/xen/arch/x86/pv/descriptor-tables.c
+++ b/xen/arch/x86/pv/descriptor-tables.c
@@ -282,6 +282,10 @@ int validate_segdesc_page(struct page_info *page)
 
     unmap_domain_page(descs);
 
+    if ( i != 512 )
+        printk_once("Check Descriptor failed: idx %u, a: %08x, b: %08x\n",
+                    i, descs[i].a, descs[i].b);
+
     return i == 512 ? 0 : -EINVAL;
 }
 
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 0459cee9fb..1059f3ce66 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -687,7 +687,7 @@ const char *trapstr(unsigned int trapnr)
     return trapnr < ARRAY_SIZE(strings) ? strings[trapnr] : "???";
 }
 
-static const char *vec_name(unsigned int vec)
+const char *vec_name(unsigned int vec)
 {
     static const char names[][4] = {
 #define P(x) [X86_EXC_ ## x] = "#" #x