linux-kernel - [PATCH 16/28] mshyperv: fix recognition of Hyper-V guest crash MSR's

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Date:	Sat,  1 Aug 2015 16:08:20 -0700
From:	"K. Y. Srinivasan" <kys@...rosoft.com>
To:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
	vkuznets@...hat.com, jasowang@...hat.com
Cc:	"Denis V. Lunev" <den@...nvz.org>,
	Andrey Smetanin <asmetanin@...tuozzo.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 16/28] mshyperv: fix recognition of Hyper-V guest crash MSR's

From: Denis V. Lunev <den@...nvz.org>

Hypervisor Top Level Functional Specification v3.1/4.0 notes that cpuid
(0x40000003) EDX's 10th bit should be used to check that Hyper-V guest
crash MSR's functionality available.

This patch should fix this recognition. Currently the code checks EAX
register instead of EDX.

Signed-off-by: Andrey Smetanin <asmetanin@...tuozzo.com>
Signed-off-by: Denis V. Lunev <den@...nvz.org>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
---
 arch/x86/include/asm/mshyperv.h |    1 +
 arch/x86/kernel/cpu/mshyperv.c  |    1 +
 drivers/hv/vmbus_drv.c          |    4 ++--
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index d02f9c9..aaf59b7 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -7,6 +7,7 @@
 
 struct ms_hyperv_info {
 	u32 features;
+	u32 misc_features;
 	u32 hints;
 };
 
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 5ea5bbc..f794bfa 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -158,6 +158,7 @@ static void __init ms_hyperv_init_platform(void)
 	 * Extract the features and hints
 	 */
 	ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
+	ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
 	ms_hyperv.hints    = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
 
 	printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 83759c1..8c3eaee 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -868,7 +868,7 @@ static int vmbus_bus_init(int irq)
 	/*
 	 * Only register if the crash MSRs are available
 	 */
-	if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
 		register_die_notifier(&hyperv_die_block);
 		atomic_notifier_chain_register(&panic_notifier_list,
 					       &hyperv_panic_block);
@@ -1313,7 +1313,7 @@ static void __exit vmbus_exit(void)
 	hv_remove_vmbus_irq();
 	tasklet_kill(&msg_dpc);
 	vmbus_free_channels();
-	if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
 		unregister_die_notifier(&hyperv_die_block);
 		atomic_notifier_chain_unregister(&panic_notifier_list,
 						 &hyperv_panic_block);
-- 
1.7.4.1

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