File 5a6703cb-x86-move-invocations-of-hvm_flush_guest_tlbs.patch of Package xen.7652

From 3e635d02d704e71534b6edf0202ed4170725a14a Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Tue, 23 Jan 2018 10:43:39 +0100
Subject: [PATCH] x86: move invocations of hvm_flush_guest_tlbs()

Their need is not tied to the actual flushing of TLBs, but the ticking
of the TLB clock. Make this more obvious by folding the two invocations
into a single one in pre_flush().

Also defer the latching of CR4 in write_cr3() until after pre_flush()
(and hence implicitly until after IRQs are off), making operation
sequence the same in both cases (eliminating the theoretical risk of
pre_flush() altering CR4). This then also improves register allocation,
as the compiler doesn't need to use a callee-saved register for "cr4"
anymore.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- sle12sp2.orig/xen/arch/x86/flushtlb.c	2016-03-14 10:18:32.000000000 +0100
+++ sle12sp2/xen/arch/x86/flushtlb.c	2018-05-23 11:23:39.000000000 +0200
@@ -50,6 +50,8 @@ static u32 pre_flush(void)
         raise_softirq(NEW_TLBFLUSH_CLOCK_PERIOD_SOFTIRQ);
 
  skip_clocktick:
+    hvm_flush_guest_tlbs();
+
     return t2;
 }
 
@@ -72,15 +74,14 @@ static void post_flush(u32 t)
 
 void write_cr3(unsigned long cr3)
 {
-    unsigned long flags, cr4 = read_cr4();
+    unsigned long flags, cr4;
     u32 t;
 
     /* This non-reentrant function is sometimes called in interrupt context. */
     local_irq_save(flags);
 
     t = pre_flush();
-
-    hvm_flush_guest_tlbs();
+    cr4 = read_cr4();
 
     write_cr4(cr4 & ~X86_CR4_PGE);
     asm volatile ( "mov %0, %%cr3" : : "r" (cr3) : "memory" );
@@ -122,8 +123,6 @@ unsigned int flush_area_local(const void
             u32 t = pre_flush();
             unsigned long cr4 = read_cr4();
 
-            hvm_flush_guest_tlbs();
-
             write_cr4(cr4 & ~X86_CR4_PGE);
             barrier();
             write_cr4(cr4);