The patch titled
paravirt: fix preemptible lazy mode bug
has been added to the -mm tree. Its filename is
paravirt-fix-preemptible-lazy-mode-bug.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: paravirt: fix preemptible lazy mode bug
From: Zachary Amsden <zach@xxxxxxxxxx>
Since set_lazy_mode(LAZY_MODE_FLUSH) is now called from the page fault
handler, it can potentially happen in a preemptible state. We therefore
must make all lazy mode paravirt-ops handlers non-preemptible.
Signed-off-by: Zachary Amsden <zach@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/vmi.c | 14 ++++++++++----
arch/i386/xen/enlighten.c | 4 +++-
2 files changed, 13 insertions(+), 5 deletions(-)
diff -puN arch/i386/kernel/vmi.c~paravirt-fix-preemptible-lazy-mode-bug arch/i386/kernel/vmi.c
--- a/arch/i386/kernel/vmi.c~paravirt-fix-preemptible-lazy-mode-bug
+++ a/arch/i386/kernel/vmi.c
@@ -555,21 +555,27 @@ vmi_startup_ipi_hook(int phys_apicid, un
static void vmi_set_lazy_mode(enum paravirt_lazy_mode mode)
{
static DEFINE_PER_CPU(enum paravirt_lazy_mode, lazy_mode);
+ int cpu;
+ enum paravirt_lazy_mode cur_mode;
if (!vmi_ops.set_lazy_mode)
return;
+ cpu = get_cpu();
+ cur_mode = per_cpu(lazy_mode, cpu);
+
/* Modes should never nest or overlap */
- BUG_ON(__get_cpu_var(lazy_mode) && !(mode == PARAVIRT_LAZY_NONE ||
- mode == PARAVIRT_LAZY_FLUSH));
+ BUG_ON(cur_mode && !(mode == PARAVIRT_LAZY_NONE ||
+ mode == PARAVIRT_LAZY_FLUSH));
if (mode == PARAVIRT_LAZY_FLUSH) {
vmi_ops.set_lazy_mode(0);
- vmi_ops.set_lazy_mode(__get_cpu_var(lazy_mode));
+ vmi_ops.set_lazy_mode(cur_mode);
} else {
vmi_ops.set_lazy_mode(mode);
- __get_cpu_var(lazy_mode) = mode;
+ per_cpu(lazy_mode, cpu) = mode;
}
+ put_cpu();
}
static inline int __init check_vmi_rom(struct vrom_header *rom)
diff -puN arch/i386/xen/enlighten.c~paravirt-fix-preemptible-lazy-mode-bug arch/i386/xen/enlighten.c
--- a/arch/i386/xen/enlighten.c~paravirt-fix-preemptible-lazy-mode-bug
+++ a/arch/i386/xen/enlighten.c
@@ -250,7 +250,7 @@ static void xen_halt(void)
static void xen_set_lazy_mode(enum paravirt_lazy_mode mode)
{
- BUG_ON(preemptible());
+ get_cpu();
switch (mode) {
case PARAVIRT_LAZY_NONE:
@@ -266,11 +266,13 @@ static void xen_set_lazy_mode(enum parav
/* flush if necessary, but don't change state */
if (x86_read_percpu(xen_lazy_mode) != PARAVIRT_LAZY_NONE)
xen_mc_flush();
+ put_cpu();
return;
}
xen_mc_flush();
x86_write_percpu(xen_lazy_mode, mode);
+ put_cpu();
}
static unsigned long xen_store_tr(void)
_
Patches currently in -mm which might be from zach@xxxxxxxxxx are
origin.patch
paravirt-fix-preemptible-lazy-mode-bug.patch
-
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