[Xen-changelog] [xen master] x86/traps: avoid interleaved writes when updating potentially-live descriptors

[patchbot@xxxxxxx]

commit 52956401df7497f3f51e3bd164ce2bb0a5cc2ee1
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Feb 11 17:17:38 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Feb 11 17:17:38 2015 +0100

    x86/traps: avoid interleaved writes when updating potentially-live 
descriptors
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/include/asm-x86/processor.h |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 2773ea8..c5c647a 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -444,9 +444,12 @@ struct __packed __cacheline_aligned tss_struct {
  * descriptor table entry. */
 static always_inline void set_ist(idt_entry_t *idt, unsigned long ist)
 {
+    idt_entry_t new = *idt;
+
     /* IST is a 3 bit field, 32 bits into the IDT entry. */
     ASSERT(ist <= IST_MAX);
-    idt->a = (idt->a & ~(7UL << 32)) | (ist << 32);
+    new.a = (idt->a & ~(7UL << 32)) | (ist << 32);
+    _write_gate_lower(idt, &new);
 }
 
 #define IDT_ENTRIES 256
--
generated by git-patchbot for /home/xen/git/xen.git#master

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