[Xen-devel] [PATCH 2/6] x86/suspend: Don't bother saving %cr3, %ss or flags

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The trampoline has already set up the idle pagetables (which are the correct
ones to use), and sanitised the flags state.

For %ss, __HYPERVISOR_DS64 is the correct descriptor to restore.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/acpi/wakeup_prot.S | 20 +++-----------------
 1 file changed, 3 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/acpi/wakeup_prot.S b/xen/arch/x86/acpi/wakeup_prot.S
index 8c525a802b..35fd7a5e9f 100644
--- a/xen/arch/x86/acpi/wakeup_prot.S
+++ b/xen/arch/x86/acpi/wakeup_prot.S
@@ -29,17 +29,10 @@ ENTRY(do_suspend_lowlevel)
         SAVE_GREG(13)
         SAVE_GREG(14)
         SAVE_GREG(15)
-        pushfq;
-        popq    SAVED_GREG(flags)
-
-        mov     %ss, REF(saved_ss)
 
         mov     %cr0, GREG(ax)
         mov     GREG(ax), REF(saved_cr0)
 
-        mov     %cr3, GREG(ax)
-        mov     GREG(ax), REF(saved_cr3)
-
         call    save_rest_processor_state
 
         /* enter sleep state physically */
@@ -55,6 +48,7 @@ ENTRY(do_suspend_lowlevel)
          *
          * The trampoline re-intercepts here.  State is:
          *  - 64bit mode
+         *  - %cr3 => idle_pg_table[]
          *
          * Everything else, including the stack, needs restoring.
          */
@@ -65,13 +59,11 @@ ENTRY(s3_resume)
         mov     REF(mmu_cr4_features), GREG(ax)
         mov     GREG(ax), %cr4
 
-        mov     REF(saved_cr3), GREG(ax)
-        mov     GREG(ax), %cr3
-
         mov     REF(saved_cr0), GREG(ax)
         mov     GREG(ax), %cr0
 
-        mov     REF(saved_ss), %ss
+        mov     $__HYPERVISOR_DS64, %eax
+        mov     %eax, %ss
         LOAD_GREG(sp)
 
         /* Reload code selector */
@@ -80,8 +72,6 @@ ENTRY(s3_resume)
         pushq   %rax
         lretq
 1:
-        pushq   SAVED_GREG(flags)
-        popfq
 
         call restore_rest_processor_state
 
@@ -109,8 +99,6 @@ ENTRY(s3_resume)
 GLOBAL(saved_magic)
         .long   0x9abcdef0
 
-saved_ss:        .word   0
-
         .align 8
 DECLARE_GREG(sp)
 DECLARE_GREG(bp)
@@ -120,7 +108,6 @@ DECLARE_GREG(cx)
 DECLARE_GREG(dx)
 DECLARE_GREG(si)
 DECLARE_GREG(di)
-DECLARE_GREG(flags)
 
 DECLARE_GREG(8)
 DECLARE_GREG(9)
@@ -132,4 +119,3 @@ DECLARE_GREG(14)
 DECLARE_GREG(15)
 
 saved_cr0:      .quad   0
-saved_cr3:      .quad   0
-- 
2.11.0


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