[Xen-changelog] [xen master] x86/tboot: disable interrupts after map_pages_to_xen() in tboot_shutdown()

[patchbot@xxxxxxx]

commit 80eb3da01bc4378af537d60e3d55767acf0d16ea
Author:     Christopher Clark <christopher.clark6@xxxxxxxxxxxxxx>
AuthorDate: Thu Aug 10 12:34:58 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Aug 10 12:34:58 2017 +0200

    x86/tboot: disable interrupts after map_pages_to_xen() in tboot_shutdown()
    
    Move the point where interrupts are disabled in tboot_shutdown
    to slightly later, to after the call to map_pages_to_xen.
    
    This patch originated in OpenXT with the following report:
    
    "Disabling interrupts early causes debug assertions.
    
    This is only seen with debug builds but since it causes assertions it is
    probably a bigger problem. It clearly says in map_pages_to_xen that it
    should not be called with interrupts disabled. Moved disabling to just
    after that call."
    
    The Xen code comment ahead of map_pages_to_xen notes that the CPU cache
    flushing in map_pages_to_xen differs depending on whether interrupts are
    enabled or not. The flush logic with interrupts enabled is more
    conservative, flushing all CPUs' TLBs/caches, rather than just local.
    This is just before the tboot memory integrity MAC calculation is performed
    in the case of entering S3.
    
    Original patch author credit: Ross Philipson.
    
    Signed-off-by: Christopher Clark <christopher.clark6@xxxxxxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/tboot.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/tboot.c b/xen/arch/x86/tboot.c
index cc26821..59d7c47 100644
--- a/xen/arch/x86/tboot.c
+++ b/xen/arch/x86/tboot.c
@@ -341,8 +341,6 @@ void tboot_shutdown(uint32_t shutdown_type)
 
     g_tboot_shared->shutdown_type = shutdown_type;
 
-    local_irq_disable();
-
     /* Create identity map for tboot shutdown code. */
     /* do before S3 integrity because mapping tboot may change xenheap */
     map_base = PFN_DOWN(g_tboot_shared->tboot_base);
@@ -357,6 +355,10 @@ void tboot_shutdown(uint32_t shutdown_type)
         return;
     }
 
+    /* Disable interrupts as early as possible but not prior to */
+    /* calling map_pages_to_xen */
+    local_irq_disable();
+
     /* if this is S3 then set regions to MAC */
     if ( shutdown_type == TB_SHUTDOWN_S3 )
     {
--
generated by git-patchbot for /home/xen/git/xen.git#master

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