[Xen-changelog] [xen staging-4.11] x86: Restore IA32_MISC_ENABLE on wakeup

[patchbot@xxxxxxx]

commit 4e95d85b991f5d7e9a881e176395340a4441b44b
Author:     MichaÅ? Kowalczyk <mkow@xxxxxxxxxxxxxxxxxxxxxx>
AuthorDate: Mon Sep 23 14:38:26 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 23 14:38:26 2019 +0200

    x86: Restore IA32_MISC_ENABLE on wakeup
    
    Code in intel.c:early_init_intel() modifies IA32_MISC_ENABLE MSR. Those
    modifications must be restored after resuming from S3 (see e.g. Linux wakeup
    code), otherwise bad things may happen (e.g. wakeup code may cause #GP when
    trying to set IA32_EFER.NXE [1]).
    
    This bug was noticed on a ThinkPad x230 with NX disabled in the BIOS:
    Xen could correctly boot, but crashed when resuming from suspend.
    Applying this patch fixed the problem.
    
    [1] Intel SDM vol 3: "If the execute-disable capability is not
    available, a write to set IA32_EFER.NXE produces a #GP exception."
    
    Signed-off-by: MichaÅ? Kowalczyk <mkow@xxxxxxxxxxxxxxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: c3cfa5b3084d71bccd8360d044bea813688b587c
    master date: 2019-08-19 15:07:34 +0100
---
 xen/arch/x86/boot/wakeup.S | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/xen/arch/x86/boot/wakeup.S b/xen/arch/x86/boot/wakeup.S
index f9632eef95..4320bb4666 100644
--- a/xen/arch/x86/boot/wakeup.S
+++ b/xen/arch/x86/boot/wakeup.S
@@ -137,6 +137,21 @@ wakeup_32:
         add     bootsym_rel(trampoline_xen_phys_start,4,%eax)
         mov     %eax,%cr3
 
+        /* Reapply IA32_MISC_ENABLE modifications from early_init_intel(). */
+        mov     bootsym_rel(trampoline_misc_enable_off, 4, %esi)
+        mov     bootsym_rel(trampoline_misc_enable_off + 4, 4, %edi)
+        mov     %esi, %eax
+        or      %edi, %eax
+        jz      1f
+        mov     $MSR_IA32_MISC_ENABLE, %ecx
+        rdmsr
+        not     %esi
+        not     %edi
+        and     %esi, %eax
+        and     %edi, %edx
+        wrmsr
+1:
+
         /* Will cpuid feature change after resume? */
         /* Set up EFER (Extended Feature Enable Register). */
         mov     bootsym_rel(cpuid_ext_features,4,%edi)
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.11

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