[v2.6.34-stable 114/213] xen/bootup: allow {read|write}_cr8 pvops call.

From: Paul Gortmaker
Date: Wed Feb 05 2014 - 15:47:01 EST


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

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------

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: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
arch/x86/xen/enlighten.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 7fa0dc02b939..1b7d744f6f30 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -779,7 +779,16 @@ static void xen_write_cr4(unsigned long cr4)

native_write_cr4(cr4);
}
-
+#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);
+}
+#endif
static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
{
int ret;
@@ -945,6 +954,11 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {
.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,
+#endif
+
.wbinvd = native_wbinvd,

.read_msr = native_read_msr_safe,
--
1.8.5.2

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