[PATCH] xen: Support 64-bit PV guest receiving NMIs

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

Zhenzhong Duan sent a patch that adds some of this functionality
but this code adds the remaining pieces. The kernel has the
logic to handle Xen-type-exceptions using the paravirt interface
in the assembler code (see PARAVIRT_ADJUST_EXCEPTION_FRAME -
pv_irq_ops.adjust_exception_frame and and INTERRUPT_RETURN -
pv_cpu_ops.iret).

That means the nmi handler (and other exception handlers) use
the hypervisor iret.

The other changes that would be neccessary for this would
be to translate the NMI_VECTOR to one of the entries on the
ipi_vector and make xen_send_IPI_mask_allbutself use different
events.

Fortunately for us commit 1db01b4903639fcfaec213701a494fe3fb2c490b
(xen: Clean up apic ipi interface) implemented this and we piggyback
on the cleanup such that the apic IPI interface will pass the right
vector value for NMI.

With this patch we can trigger NMIs within a PV guest (only tested
x86_64).

SysRq : Show backtrace of all active CPUs
sending NMI to all CPUs:
NMI backtrace for cpu 2
CPU 2
RIP: e030:[<ffffffff8100130a>]  [<ffffffff8100130a>] xen_hypercall_vcpu_op+0xa/0x20
. snip..
Call Trace:
 [<ffffffff813afdc0>] ? xen_send_IPI_one+0x40/0x60
 [<ffffffff8104bdcb>] __xen_send_IPI_mask+0x2b/0x50
 [<ffffffff8104c6f9>] xen_send_IPI_all+0x79/0xa0
 [<ffffffff81074df9>] arch_trigger_all_cpu_backtrace+0x59/0xa0
 [<ffffffff813d16f9>] sysrq_handle_showallcpus+0x9/0x10
 [<ffffffff813d1ad9>] __handle_sysrq+0x129/0x190
 [<ffffffff813d1b40>] ? __handle_sysrq+0x190/0x190
 [<ffffffff813d1ba4>] write_sysrq_trigger+0x64/0x70
 [<ffffffff8121211b>] proc_reg_write+0x8b/0xe0
 [<ffffffff811aa1c4>] vfs_write+0xb4/0x130
 [<ffffffff811aa98a>] sys_write+0x5a/0xa0
 [<ffffffff816825e9>] system_call_fastpath+0x16/0x1b
NMI backtrace for cpu 0
CPU 0
. snip..
Call Trace:
 [<ffffffff81044180>] ? xen_safe_halt+0x10/0x20
 [<ffffffff8105746c>] default_idle+0x3c/0x130
 [<ffffffff81056cf9>] cpu_idle+0x99/0xe0
 [<ffffffff816619da>] rest_init+0x8a/0xa0
 [<ffffffff81ac10a4>] start_kernel+0x3da/0x3e7
 [<ffffffff81ac0ae8>] ? repair_env_string+0x5b/0x5b
 [<ffffffff81ac05f7>] x86_64_start_reservations+0x2a/0x2c
 [<ffffffff81ac30ce>] xen_start_kernel+0x56e/0x570
NMI backtrace for cpu 1
CPU 1
RIP: e030:[<ffffffff810013aa>]  [<ffffffff810013aa>] xen_hypercall_sched_op+0xa/0x20
.snip..
Call Trace:
 [<ffffffff81044180>] ? xen_safe_halt+0x10/0x20
 [<ffffffff8105746c>] default_idle+0x3c/0x130
 [<ffffffff81056cf9>] cpu_idle+0x99/0xe0
 [<ffffffff81044969>] ? xen_irq_enable_direct_reloc+0x4/0x4
 [<ffffffff8166801b>] cpu_bringup_and_idle+0xe/0x10
NMI backtrace for cpu 3
CPU 3
.snip..
Call Trace:
 [<ffffffff81044180>] ? xen_safe_halt+0x10/0x20
 [<ffffffff8105746c>] default_idle+0x3c/0x130
 [<ffffffff81056cf9>] cpu_idle+0x99/0xe0
 [<ffffffff81044969>] ? xen_irq_enable_direct_reloc+0x4/0x4
 [<ffffffff8166801b>] cpu_bringup_and_idle+0xe/0x10

Incidentally that means kgdb will also now work within
a PV guest without using the 'nokgdbroundup' workaround.

Note that the 32-bit version is different and this patch
does not enable that.

CC: Lisa Nguyen <lisa@xenapiadmin.com>
CC: Ben Guthro <benjamin.guthro@citrix.com>
CC: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/include/asm/xen/events.h |    1 +
 arch/x86/xen/enlighten.c          |   13 ++++++++-----
 arch/x86/xen/setup.c              |   13 +++++++++++--
 arch/x86/xen/smp.c                |    5 +++++
 drivers/xen/events.c              |   11 +++++++++++
 include/xen/interface/vcpu.h      |    2 ++
 6 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/xen/events.h b/arch/x86/include/asm/xen/events.h
index ca842f2..608a79d 100644
--- a/arch/x86/include/asm/xen/events.h
+++ b/arch/x86/include/asm/xen/events.h
@@ -7,6 +7,7 @@ enum ipi_vector {
 	XEN_CALL_FUNCTION_SINGLE_VECTOR,
 	XEN_SPIN_UNLOCK_VECTOR,
 	XEN_IRQ_WORK_VECTOR,
+	XEN_NMI_VECTOR,
 
 	XEN_NR_IPIS,
 };
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 2fa02bc..231382a 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -427,8 +427,7 @@ static void __init xen_init_cpuid_mask(void)
 
 	if (!xen_initial_domain())
 		cpuid_leaf1_edx_mask &=
-			~((1 << X86_FEATURE_APIC) |  /* disable local APIC */
-			  (1 << X86_FEATURE_ACPI));  /* disable ACPI */
+			~((1 << X86_FEATURE_ACPI));  /* disable ACPI */
 
 	cpuid_leaf1_ecx_mask &= ~(1 << (X86_FEATURE_X2APIC % 32));
 
@@ -735,8 +734,7 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
 		addr = (unsigned long)xen_int3;
 	else if (addr == (unsigned long)stack_segment)
 		addr = (unsigned long)xen_stack_segment;
-	else if (addr == (unsigned long)double_fault ||
-		 addr == (unsigned long)nmi) {
+	else if (addr == (unsigned long)double_fault) {
 		/* Don't need to handle these */
 		return 0;
 #ifdef CONFIG_X86_MCE
@@ -747,7 +745,12 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
 		 */
 		;
 #endif
-	} else {
+	} else if (addr == (unsigned long)nmi)
+		/*
+		 * Use the native version as well.
+		 */
+		;
+	else {
 		/* Some other trap using IST? */
 		if (WARN_ON(val->ist != 0))
 			return 0;
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 94eac5c..f78877c 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -33,6 +33,9 @@
 /* These are code, but not functions.  Defined in entry.S */
 extern const char xen_hypervisor_callback[];
 extern const char xen_failsafe_callback[];
+#ifdef CONFIG_X86_64
+extern const char nmi[];
+#endif
 extern void xen_sysenter_target(void);
 extern void xen_syscall_target(void);
 extern void xen_syscall32_target(void);
@@ -525,7 +528,13 @@ void __cpuinit xen_enable_syscall(void)
 	}
 #endif /* CONFIG_X86_64 */
 }
-
+void __cpuinit xen_enable_nmi(void)
+{
+#ifdef CONFIG_X86_64
+	if (register_callback(CALLBACKTYPE_nmi, nmi))
+		BUG();
+#endif
+}
 void __init xen_arch_setup(void)
 {
 	xen_panic_handler_init();
@@ -543,7 +552,7 @@ void __init xen_arch_setup(void)
 
 	xen_enable_sysenter();
 	xen_enable_syscall();
-
+	xen_enable_nmi();
 #ifdef CONFIG_ACPI
 	if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
 		printk(KERN_INFO "ACPI in unprivileged domain disabled\n");
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index c1367b2..d792cce 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -572,6 +572,10 @@ static inline int xen_map_vector(int vector)
 	case IRQ_WORK_VECTOR:
 		xen_vector = XEN_IRQ_WORK_VECTOR;
 		break;
+	case NMI_VECTOR:
+	case APIC_DM_NMI:
+		xen_vector = XEN_NMI_VECTOR;
+		break;
 	default:
 		xen_vector = -1;
 		printk(KERN_ERR "xen: vector 0x%x is not implemented\n",
@@ -659,6 +663,7 @@ static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+
 static const struct smp_ops xen_smp_ops __initconst = {
 	.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
 	.smp_prepare_cpus = xen_smp_prepare_cpus,
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index a58ac43..419cc44 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -56,6 +56,7 @@
 #include <xen/interface/hvm/params.h>
 #include <xen/interface/physdev.h>
 #include <xen/interface/sched.h>
+#include <xen/interface/vcpu.h>
 #include <asm/hw_irq.h>
 
 /*
@@ -1213,6 +1214,16 @@ EXPORT_SYMBOL_GPL(evtchn_put);
 void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
 {
 	int irq = per_cpu(ipi_to_irq, cpu)[vector];
+
+	/*
+	 * In which the IRQ will be -1.
+	 */
+	if (unlikely(vector == XEN_NMI_VECTOR)) {
+		int rc =  HYPERVISOR_vcpu_op(VCPUOP_send_nmi, cpu, NULL);
+		if (rc < 0)
+			printk(KERN_WARNING "Sending nmi to CPU%d failed (rc:%d)\n", cpu, rc);
+		return;
+	}
 	BUG_ON(irq < 0);
 	notify_remote_via_irq(irq);
 }
diff --git a/include/xen/interface/vcpu.h b/include/xen/interface/vcpu.h
index 87e6f8a..b05288c 100644
--- a/include/xen/interface/vcpu.h
+++ b/include/xen/interface/vcpu.h
@@ -170,4 +170,6 @@ struct vcpu_register_vcpu_info {
 };
 DEFINE_GUEST_HANDLE_STRUCT(vcpu_register_vcpu_info);
 
+/* Send an NMI to the specified VCPU. @extra_arg == NULL. */
+#define VCPUOP_send_nmi             11
 #endif /* __XEN_PUBLIC_VCPU_H__ */
-- 
1.7.7.6