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Subject[PATCH 4.15 036/122] x86/xen: Zero MSR_IA32_SPEC_CTRL before suspend
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Juergen Gross <jgross@suse.com>

commit 71c208dd54ab971036d83ff6d9837bae4976e623 upstream.

Older Xen versions (4.5 and before) might have problems migrating pv
guests with MSR_IA32_SPEC_CTRL having a non-zero value. So before
suspending zero that MSR and restore it after being resumed.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Cc: stable@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Cc: boris.ostrovsky@oracle.com
Link: https://lkml.kernel.org/r/20180226140818.4849-1-jgross@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/xen/suspend.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -1,12 +1,15 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/tick.h>
+#include <linux/percpu-defs.h>

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/grant_table.h>
#include <xen/events.h>

+#include <asm/cpufeatures.h>
+#include <asm/msr-index.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/page.h>
#include <asm/fixmap.h>
@@ -15,6 +18,8 @@
#include "mmu.h"
#include "pmu.h"

+static DEFINE_PER_CPU(u64, spec_ctrl);
+
void xen_arch_pre_suspend(void)
{
xen_save_time_memory_area();
@@ -35,6 +40,9 @@ void xen_arch_post_suspend(int cancelled

static void xen_vcpu_notify_restore(void *data)
{
+ if (xen_pv_domain() && boot_cpu_has(X86_FEATURE_SPEC_CTRL))
+ wrmsrl(MSR_IA32_SPEC_CTRL, this_cpu_read(spec_ctrl));
+
/* Boot processor notified via generic timekeeping_resume() */
if (smp_processor_id() == 0)
return;
@@ -44,7 +52,15 @@ static void xen_vcpu_notify_restore(void

static void xen_vcpu_notify_suspend(void *data)
{
+ u64 tmp;
+
tick_suspend_local();
+
+ if (xen_pv_domain() && boot_cpu_has(X86_FEATURE_SPEC_CTRL)) {
+ rdmsrl(MSR_IA32_SPEC_CTRL, tmp);
+ this_cpu_write(spec_ctrl, tmp);
+ wrmsrl(MSR_IA32_SPEC_CTRL, 0);
+ }
}

void xen_arch_resume(void)

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