[PATCH 4/4] xen/acpi: Prep saved_context cr3 values.

From: Konrad Rzeszutek Wilk
Date: Wed Oct 17 2012 - 10:03:52 EST

When save_processor_state is executed it executes a bunch of
pvops calls to save the CPU state values. When it comes back
from Xen's S3 (so acpi_enter_sleep_state, which ends up calling
xen_acpi_notify_hypervisor_state), it ends up back in the
assembler code in wakeup_[32|64].S. It skips the wakeup
calls (so wakeup_pmode_return and wakeup_long64) as that has
been done in the hypervisor. Instead it continues on in
the resume_point (64-bit) or ret_point (32-bit). Most of the
calls in there are safe to be executed except when it comes to
reloading of cr3 (which it only does on 64-bit kernels). Since
they are native assembler calls and Xen expects a PV kernel to
prep those to use machine address for cr3 that is what
we are going to do. Note: that it is not Machine Frame Numbers
(those are used in the MMUEXT_NEW_BASEPTR hypercall for cr3
installation) but the machine physical address.

When the assembler code executes this mov %ebx, cr3 it ends
end up trapped in the hypervisor (traps.c) which properly now
sets the cr3 value.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
drivers/xen/acpi.c | 25 +++++++++++++++++++++++++
1 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/drivers/xen/acpi.c b/drivers/xen/acpi.c
index 119d42a..25e612c 100644
--- a/drivers/xen/acpi.c
+++ b/drivers/xen/acpi.c
@@ -35,6 +35,13 @@
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

+#include <xen/page.h>
+#ifdef CONFIG_X86_64
+#include <asm/suspend_64.h>
+extern struct saved_context saved_context;
int xen_acpi_notify_hypervisor_state(u8 sleep_state,
u32 pm1a_cnt, u32 pm1b_cnt)
@@ -56,7 +63,25 @@ int xen_acpi_notify_hypervisor_state(u8 sleep_state,
pm1a_cnt, pm1b_cnt);
return -1;
+#ifdef CONFIG_X86_64
+ /* We do not need to anything for 32-bit kernels as the
+ * low-level calls (write to cr3) is done in the wakup code
+ * which we never execute when running under Xen.
+ */
+ {
+ unsigned long mfn;

+ /* resume_point in wakeup_64.s barrels through and does:
+ * movq saved_context_cr3(%rax), %rbx
+ * movq %rbx, %cr3
+ * so lets prep the values so they are OK with the
+ * hypervisor. */
+ mfn = pfn_to_mfn(PFN_DOWN(saved_context.cr3));
+ /* and back to a physical address */
+ mfn = PFN_PHYS(mfn);
+ saved_context.cr3 = mfn;
+ }
return 1;

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