linux-kernel - [PATCH] xen/pvhvm: add soft reset on kexec/kdump support

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Date:	Fri, 25 Sep 2015 11:59:52 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	xen-devel@...ts.xenproject.org, x86@...nel.org
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] xen/pvhvm: add soft reset on kexec/kdump support

Currently there is a number of issues preventing PVHVM Xen guests from
doing successful kexec/kdump:
- Bound event channels.
- Registered vcpu_info.
- PIRQ/emuirq mappings.
- shared_info frame after XENMAPSPACE_shared_info operation.
- Active grant mappings.
Basically, newly booted kernel stumbles upon already set up Xen interfaces
and there is no way to reestablish them. In Xen-4.7 a new feature called
'soft reset' is coming. A guest performing kexec/kdump operation is
supposed to call SCHEDOP_shutdown hypercall with SHUTDOWN_soft_reset reason
before jumping to new kernel. Hypervisor (with some help from toolstack)
will do full domain cleanup (but keeping its memory and vCPU contexts
intact) returning the guest to the state it had when it was first booted
and thus allowing it to start over.

Doing SHUTDOWN_soft_reset on Xen hypervisors which don't support it is
probably OK as by default all unknown shutdown reasons cause domain destroy
with a message in toolstack log:
'Unknown shutdown reason code 5. Destroying domain.'
which gives a clue to what the problem is and eliminates false
expectations.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/xen/enlighten.c      | 23 +++++++++++++++++++++++
 include/xen/interface/sched.h |  8 ++++++++
 2 files changed, 31 insertions(+)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 30d12af..e4be074 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -33,6 +33,10 @@
 #include <linux/memblock.h>
 #include <linux/edd.h>
 
+#ifdef CONFIG_KEXEC_CORE
+#include <linux/kexec.h>
+#endif
+
 #include <xen/xen.h>
 #include <xen/events.h>
 #include <xen/interface/xen.h>
@@ -1807,6 +1811,21 @@ static struct notifier_block xen_hvm_cpu_notifier = {
 	.notifier_call	= xen_hvm_cpu_notify,
 };
 
+#ifdef CONFIG_KEXEC_CORE
+static void xen_pvhvm_kexec_shutdown(void)
+{
+	native_machine_shutdown();
+	if (kexec_in_progress)
+		xen_reboot(SHUTDOWN_soft_reset);
+}
+
+static void xen_pvhvm_crash_shutdown(struct pt_regs *regs)
+{
+	native_machine_crash_shutdown(regs);
+	xen_reboot(SHUTDOWN_soft_reset);
+}
+#endif
+
 static void __init xen_hvm_guest_init(void)
 {
 	if (xen_pv_domain())
@@ -1826,6 +1845,10 @@ static void __init xen_hvm_guest_init(void)
 	x86_init.irqs.intr_init = xen_init_IRQ;
 	xen_hvm_init_time_ops();
 	xen_hvm_init_mmu_ops();
+#ifdef CONFIG_KEXEC_CORE
+	machine_ops.shutdown = xen_pvhvm_kexec_shutdown;
+	machine_ops.crash_shutdown = xen_pvhvm_crash_shutdown;
+#endif
 }
 #endif
 
diff --git a/include/xen/interface/sched.h b/include/xen/interface/sched.h
index 9ce0839..f184909 100644
--- a/include/xen/interface/sched.h
+++ b/include/xen/interface/sched.h
@@ -107,5 +107,13 @@ struct sched_watchdog {
 #define SHUTDOWN_suspend    2  /* Clean up, save suspend info, kill.         */
 #define SHUTDOWN_crash      3  /* Tell controller we've crashed.             */
 #define SHUTDOWN_watchdog   4  /* Restart because watchdog time expired.     */
+/*
+ * Domain asked to perform 'soft reset' for it. The expected behavior is to
+ * reset internal Xen state for the domain returning it to the point where it
+ * was created but leaving the domain's memory contents and vCPU contexts
+ * intact. This will allow the domain to start over and set up all Xen specific
+ * interfaces again.
+ */
+#define SHUTDOWN_soft_reset 5
 
 #endif /* __XEN_PUBLIC_SCHED_H__ */
-- 
2.4.3

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