[Xen-changelog] [xen stable-4.9] x86: suppress BTI mitigations around S3 suspend/resume

[patchbot@xxxxxxx]

commit 62bd851a4469976f036c2d804ebed7ca39741254
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri May 18 11:53:13 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri May 18 11:53:13 2018 +0200

    x86: suppress BTI mitigations around S3 suspend/resume
    
    NMI and #MC can occur at any time after S3 resume, yet the MSR_SPEC_CTRL
    may become available only once we're reloaded microcode. Make
    SPEC_CTRL_ENTRY_FROM_INTR_IST and DO_SPEC_CTRL_EXIT_TO_XEN no-ops for
    the critical period of time.
    
    Also set the MSR back to its intended value.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    
    x86: Use spec_ctrl_{enter,exit}_idle() in the S3/S5 path
    
    The main purpose of this patch is to avoid opencoding the recovery logic at
    the end, but also has the positive side effect of relaxing the SPEC_CTRL
    mitigations when working to shut the final CPU down.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 710a8ebf2bc111a34bba04d1c85b6d07ed3d9389
    master date: 2018-04-16 14:09:55 +0200
    master commit: ef3ab46493f650b7e5cca2b2578a99ca0cbff195
    master date: 2018-04-19 10:55:59 +0100
---
 xen/arch/x86/acpi/power.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index cb06f842cd..f7085d3c7b 100644
--- a/xen/arch/x86/acpi/power.c
+++ b/xen/arch/x86/acpi/power.c
@@ -28,6 +28,7 @@
 #include <asm/tboot.h>
 #include <asm/apic.h>
 #include <asm/io_apic.h>
+#include <asm/spec_ctrl.h>
 #include <acpi/cpufreq/cpufreq.h>
 
 uint32_t system_reset_counter = 1;
@@ -163,6 +164,7 @@ static int enter_state(u32 state)
 {
     unsigned long flags;
     int error;
+    struct cpu_info *ci;
     unsigned long cr4;
 
     if ( (state <= ACPI_STATE_S0) || (state > ACPI_S_STATES_MAX) )
@@ -210,6 +212,11 @@ static int enter_state(u32 state)
     else
         error = 0;
 
+    ci = get_cpu_info();
+    spec_ctrl_enter_idle(ci);
+    /* Avoid NMI/#MC using MSR_SPEC_CTRL until we've reloaded microcode. */
+    ci->bti_ist_info = 0;
+
     ACPI_FLUSH_CPU_CACHE();
 
     switch ( state )
@@ -248,6 +255,10 @@ static int enter_state(u32 state)
 
     microcode_resume_cpu(0);
 
+    /* Re-enabled default NMI/#MC use of MSR_SPEC_CTRL. */
+    ci->bti_ist_info = default_bti_ist_info;
+    spec_ctrl_exit_idle(ci);
+
  done:
     spin_debug_enable();
     local_irq_restore(flags);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.9

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