FRED provides %cr2 in the the stack frame, avoiding the need to read %cr2
manually.

Rename do_page_fault() to handle_PF(), and update it to take cr2, still named
addr for consistency.

Introduce a new handle_PF_IDT() which reads %cr2 and conditionally re-enables
interrupts.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>

v2:
 * New
---
 xen/arch/x86/traps.c        | 26 ++++++++++++++------------
 xen/arch/x86/x86_64/entry.S |  2 +-
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 3fd0f5709a52..d42973660db0 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1670,21 +1670,10 @@ static int fixup_page_fault(unsigned long addr, struct cpu_user_regs *regs)
     return 0;
 }
 
-void asmlinkage do_page_fault(struct cpu_user_regs *regs)
+static void handle_PF(struct cpu_user_regs *regs, unsigned long addr /* cr2 */)
 {
-    unsigned long addr;
     unsigned int error_code;
 
-    addr = read_cr2();
-
-    /*
-     * Don't re-enable interrupts if we were running an IRQ-off region when
-     * we hit the page fault, or we'll break that code.
-     */
-    ASSERT(!local_irq_is_enabled());
-    if ( regs->flags & X86_EFLAGS_IF )
-        local_irq_enable();
-
     /* fixup_page_fault() might change regs->error_code, so cache it here. */
     error_code = regs->error_code;
 
@@ -1745,6 +1734,19 @@ void asmlinkage do_page_fault(struct cpu_user_regs *regs)
     pv_inject_page_fault(regs->error_code, addr);
 }
 
+/*
+ * When using IDT delivery, it is our responsibility to read %cr2.
+ */
+void asmlinkage handle_PF_IDT(struct cpu_user_regs *regs)
+{
+    unsigned long addr = read_cr2();
+
+    if ( regs->flags & X86_EFLAGS_IF )
+        local_irq_enable();
+
+    handle_PF(regs, addr);
+}
+
 /*
  * Early #PF handler to print CR2, error code, and stack.
  *
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 789687488c5f..c02245ac064c 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -871,7 +871,7 @@ handle_exception_saved:
          * reading %cr2. Otherwise a page fault in the nested interrupt handler
          * would corrupt %cr2.
          */
-        DISPATCH(X86_EXC_PF, do_page_fault)
+        DISPATCH(X86_EXC_PF, handle_PF_IDT)
 
         /* Only re-enable IRQs if they were active before taking the fault */
         testb $X86_EFLAGS_IF >> 8, UREGS_eflags + 1(%rsp)
-- 
2.39.5