[ 37/76] xen/bootup: allow {read|write}_cr8 pvops call.

From: Greg Kroah-Hartman
Date: Thu Oct 18 2012 - 22:59:12 EST

3.6-stable review patch. If anyone has any objections, please let me know.


From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

commit 1a7bbda5b1ab0e02622761305a32dc38735b90b2 upstream.

We actually do not do anything about it. Just return a default
value of zero and if the kernel tries to write anything but 0
we BUG_ON.

This fixes the case when an user tries to suspend the machine
and it blows up in save_processor_state b/c 'read_cr8' is set
to NULL and we get:

kernel BUG at /home/konrad/ssd/linux/arch/x86/include/asm/paravirt.h:100!
invalid opcode: 0000 [#1] SMP
Pid: 2687, comm: init.late Tainted: G O 3.6.0upstream-00002-gac264ac-dirty #4 Bochs Bochs
RIP: e030:[<ffffffff814d5f42>] [<ffffffff814d5f42>] save_processor_state+0x212/0x270

.. snip..
Call Trace:
[<ffffffff810733bf>] do_suspend_lowlevel+0xf/0xac
[<ffffffff8107330c>] ? x86_acpi_suspend_lowlevel+0x10c/0x150
[<ffffffff81342ee2>] acpi_suspend_enter+0x57/0xd5

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/xen/enlighten.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -984,7 +984,16 @@ static void xen_write_cr4(unsigned long

+#ifdef CONFIG_X86_64
+static inline unsigned long xen_read_cr8(void)
+ return 0;
+static inline void xen_write_cr8(unsigned long val)
+ BUG_ON(val);
static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
int ret;
@@ -1153,6 +1162,11 @@ static const struct pv_cpu_ops xen_cpu_o
.read_cr4_safe = native_read_cr4_safe,
.write_cr4 = xen_write_cr4,

+#ifdef CONFIG_X86_64
+ .read_cr8 = xen_read_cr8,
+ .write_cr8 = xen_write_cr8,
.wbinvd = native_wbinvd,

.read_msr = native_read_msr_safe,

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