[PATCH 2/2] Revert pad config check in xen_check_mwait

[Liu , Jinsong]

With Xen acpi pad logic added into kernel, we can now revert xen mwait rela=
ted
patch df88b2d96e36d9a9e325bfcd12eb45671cbbc937. The reason is, when running=
 under
newer Xen platform, Xen pad driver would be early loaded, so native pad dri=
ver
would fail to be loaded, and hence no mwait/monitor #UD risk again.

Another point is, only Xen4.2 or later support Xen acpi pad, so we won't ex=
pose
mwait cpuid capability when running under older Xen platform.

Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
---
 arch/x86/xen/enlighten.c |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 586d838..9e22e41 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -287,8 +287,7 @@ static void xen_cpuid(unsigned int *ax, unsigned int *b=
x,
=20
 static bool __init xen_check_mwait(void)
 {
-#if defined(CONFIG_ACPI) && !defined(CONFIG_ACPI_PROCESSOR_AGGREGATOR) && =
\
-	!defined(CONFIG_ACPI_PROCESSOR_AGGREGATOR_MODULE)
+#ifdef CONFIG_ACPI
 	struct xen_platform_op op =3D {
 		.cmd			=3D XENPF_set_processor_pminfo,
 		.u.set_pminfo.id	=3D -1,
@@ -297,6 +296,10 @@ static bool __init xen_check_mwait(void)
 	uint32_t buf[3];
 	unsigned int ax, bx, cx, dx;
 	unsigned int mwait_mask;
+	unsigned int version =3D HYPERVISOR_xen_version(XENVER_version, NULL);
+	unsigned int major =3D version >> 16;
+	unsigned int minor =3D version & 0xffff;
+
=20
 	/* We need to determine whether it is OK to expose the MWAIT
 	 * capability to the kernel to harvest deeper than C3 states from ACPI
@@ -309,6 +312,13 @@ static bool __init xen_check_mwait(void)
 	if (!xen_initial_domain())
 		return false;
=20
+	/*
+	 * When running under platform earlier than Xen4.2, do not expose
+	 * mwait, to avoid the risk of loading native acpi pad driver
+	 */
+	if (((major =3D=3D 4) && (minor < 2)) || (major < 4))
+		return false;
+
 	ax =3D 1;
 	cx =3D 0;
=20
--=20
1.7.1

--_002_DE8DF0795D48FD4CA783C40EC829233537735CSHSMSX101ccrcorpi_
Content-Type: application/octet-stream;
	name="0002-Revert-pad-config-check-in-xen_check_mwait.patch"
Content-Description: 0002-Revert-pad-config-check-in-xen_check_mwait.patch
Content-Disposition: attachment;
	filename="0002-Revert-pad-config-check-in-xen_check_mwait.patch"; size=2139;
	creation-date="Thu, 01 Nov 2012 06:25:57 GMT";
	modification-date="Thu, 01 Nov 2012 13:29:12 GMT"
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--_002_DE8DF0795D48FD4CA783C40EC829233537735CSHSMSX101ccrcorpi_--
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