[Xen-devel] [PATCH 4/6] x86/suspend: Restore cr4 later during resume

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Just like the BSP/AP paths, %cr4 is loaded with only PAE.  Defer restoring all
of %cr4 (MCE in particular) until all the system structures (IDT/TSS in
particular) have been loaded.

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/suspend.c     | 3 +++
 xen/arch/x86/acpi/wakeup_prot.S | 4 ----
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/acpi/suspend.c b/xen/arch/x86/acpi/suspend.c
index c9dea67bf3..32d0f71ffd 100644
--- a/xen/arch/x86/acpi/suspend.c
+++ b/xen/arch/x86/acpi/suspend.c
@@ -43,6 +43,9 @@ void restore_rest_processor_state(void)
 {
     load_system_tables();
 
+    /* Restore full CR4 (inc MCE) now that the IDT is in place. */
+    write_cr4(mmu_cr4_features);
+
     /* Recover syscall MSRs */
     wrmsrl(MSR_LSTAR, saved_lstar);
     wrmsrl(MSR_CSTAR, saved_cstar);
diff --git a/xen/arch/x86/acpi/wakeup_prot.S b/xen/arch/x86/acpi/wakeup_prot.S
index 2f6c8e18ef..a81849fd2b 100644
--- a/xen/arch/x86/acpi/wakeup_prot.S
+++ b/xen/arch/x86/acpi/wakeup_prot.S
@@ -45,10 +45,6 @@ ENTRY(do_suspend_lowlevel)
 ENTRY(s3_resume)
         lgdt    boot_gdtr(%rip)
 
-        /* mmu_cr4_features contains latest cr4 setting */
-        mov     REF(mmu_cr4_features), GREG(ax)
-        mov     GREG(ax), %cr4
-
         mov     REF(saved_cr0), GREG(ax)
         mov     GREG(ax), %cr0
 
-- 
2.11.0


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