linux-kernel - [PATCH 2/5 V4] Add functions to check if the host has stopped the vm

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Message-Id: <1322602539-27004-3-git-send-email-emunson@mgebm.net>
Date:	Tue, 29 Nov 2011 16:35:36 -0500
From:	Eric B Munson <emunson@...bm.net>
To:	avi@...hat.com
Cc:	Eric B Munson <emunson@...bm.net>, mingo@...hat.com, hpa@...or.com,
	arnd@...db.de, ryanh@...ux.vnet.ibm.com, aliguori@...ibm.com,
	mtosatti@...hat.com, jeremy.fitzhardinge@...rix.com,
	kvm@...r.kernel.org, linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/5 V4] Add functions to check if the host has stopped the vm

When a host stops or suspends a VM it will set a flag to show this.  The
watchdog will use these functions to determine if a softlockup is real, or the
result of a suspended VM.

Signed-off-by: Eric B Munson <emunson@...bm.net>
Cc: mingo@...hat.com
Cc: hpa@...or.com
Cc: arnd@...db.de
Cc: ryanh@...ux.vnet.ibm.com
Cc: aliguori@...ibm.com
Cc: mtosatti@...hat.com
Cc: jeremy.fitzhardinge@...rix.com
Cc: kvm@...r.kernel.org
Cc: linux-arch@...r.kernel.org
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
 arch/x86/include/asm/kvm_para.h |    1 +
 arch/x86/kernel/kvmclock.c      |   21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 734c376..e9d63a6 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -95,6 +95,7 @@ struct kvm_vcpu_pv_apf_data {
 extern void kvmclock_init(void);
 extern int kvm_register_clock(char *txt);
 
+bool kvm_check_and_clear_guest_paused(int cpu);
 
 /* This instruction is vmcall.  On non-VT architectures, it will generate a
  * trap that we will then rewrite to the appropriate instruction.
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 44842d7..f0c0599 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -22,6 +22,7 @@
 #include <asm/msr.h>
 #include <asm/apic.h>
 #include <linux/percpu.h>
+#include <linux/hardirq.h>
 
 #include <asm/x86_init.h>
 #include <asm/reboot.h>
@@ -114,6 +115,26 @@ static void kvm_get_preset_lpj(void)
 	preset_lpj = lpj;
 }
 
+bool kvm_check_and_clear_guest_paused(int cpu)
+{
+	bool ret = false;
+	struct pvclock_vcpu_time_info *src;
+
+	/*
+	 * per_cpu() is safe here because this function is only called from
+	 * timer functions where preemption is already disabled.
+	 */
+	WARN_ON(!in_atomic());
+	src = &per_cpu(hv_clock, cpu);
+	if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
+		src->flags = src->flags & (~PVCLOCK_GUEST_STOPPED);
+		ret = true;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kvm_check_and_clear_guest_paused);
+
 static struct clocksource kvm_clock = {
 	.name = "kvm-clock",
 	.read = kvm_clock_get_cycles,
-- 
1.7.5.4

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