Re: [Xen-devel] [PATCH 2/2] Revert pad config check in xen_check_mwait

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

Updated, adding version check at mwait routine.

Thanks,
Jinsong

============
>From 27e28963d4d25e4c998b5b5ea3828a02e6de9470 Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
Date: Thu, 1 Nov 2012 21:18:43 +0800
Subject: [PATCH 2/2] Revert pad config check in xen_check_mwait

With Xen acpi pad logic added into kernel, we can now revert xen mwait related
patch df88b2d96e36d9a9e325bfcd12eb45671cbbc937. The reason is, when running 
under
newer Xen platform, Xen pad driver would be early loaded, so native pad driver
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 expose
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 *bx,
 
 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 = {
                .cmd                    = XENPF_set_processor_pminfo,
                .u.set_pminfo.id        = -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 = HYPERVISOR_xen_version(XENVER_version, NULL);
+       unsigned int major = version >> 16;
+       unsigned int minor = version & 0xffff;
+
 
        /* 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;
 
+       /*
+        * When running under platform earlier than Xen4.2, do not expose
+        * mwait, to avoid the risk of loading native acpi pad driver
+        */
+       if (((major == 4) && (minor < 2)) || (major < 4))
+               return false;
+
        ax = 1;
        cx = 0;
 
-- 
1.7.1

Attachment: 0002-Revert-pad-config-check-in-xen_check_mwait.patch
Description: 0002-Revert-pad-config-check-in-xen_check_mwait.patch

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