[Xen-changelog] [xen stable-4.6] x86: move invocations of hvm_flush_guest_tlbs()

[patchbot@xxxxxxx]

commit 331a1af09bafd77d9e25c415e089ba921e51b456
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Jan 23 10:43:39 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 29 11:10:06 2018 +0200

    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@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/flushtlb.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/flushtlb.c b/xen/arch/x86/flushtlb.c
index e2a5524964..7d5a81576f 100644
--- a/xen/arch/x86/flushtlb.c
+++ b/xen/arch/x86/flushtlb.c
@@ -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" );
@@ -118,8 +119,6 @@ void flush_area_local(const void *va, unsigned int flags)
             u32 t = pre_flush();
             unsigned long cr4 = read_cr4();
 
-            hvm_flush_guest_tlbs();
-
             write_cr4(cr4 & ~X86_CR4_PGE);
             barrier();
             write_cr4(cr4);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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