netdev - [PATCH v3] xen-apic: Enable on domU as well

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Message-Id: <1439214027-13994-1-git-send-email-Jason@zx2c4.com>
Date:	Mon, 10 Aug 2015 15:40:27 +0200
From:	"Jason A. Donenfeld" <Jason@...c4.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	Ian Campbell <ian.campbell@...rix.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org
Cc:	"Jason A. Donenfeld" <Jason@...c4.com>, <stable@...r.kernel.org>
Subject: [PATCH v3] xen-apic: Enable on domU as well

It turns out that domU also requires the Xen APIC driver. Otherwise we
get stuck in busy loops that never exit, such as in this stack trace:

(gdb) target remote localhost:9999
Remote debugging using localhost:9999
__xapic_wait_icr_idle () at ./arch/x86/include/asm/ipi.h:56
56              while (native_apic_mem_read(APIC_ICR) & APIC_ICR_BUSY)
(gdb) bt
 #0  __xapic_wait_icr_idle () at ./arch/x86/include/asm/ipi.h:56
 #1  __default_send_IPI_shortcut (shortcut=<optimized out>,
dest=<optimized out>, vector=<optimized out>) at
./arch/x86/include/asm/ipi.h:75
 #2  apic_send_IPI_self (vector=246) at arch/x86/kernel/apic/probe_64.c:54
 #3  0xffffffff81011336 in arch_irq_work_raise () at
arch/x86/kernel/irq_work.c:47
 #4  0xffffffff8114990c in irq_work_queue (work=0xffff88000fc0e400) at
kernel/irq_work.c:100
 #5  0xffffffff8110c29d in wake_up_klogd () at kernel/printk/printk.c:2633
 #6  0xffffffff8110ca60 in vprintk_emit (facility=0, level=<optimized
out>, dict=0x0 <irq_stack_union>, dictlen=<optimized out>,
fmt=<optimized out>, args=<optimized out>)
    at kernel/printk/printk.c:1778
 #7  0xffffffff816010c8 in printk (fmt=<optimized out>) at
kernel/printk/printk.c:1868
 #8  0xffffffffc00013ea in ?? ()
 #9  0x0000000000000000 in ?? ()

Mailing-list-thread: https://lkml.org/lkml/2015/8/4/755
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Cc: David Vrabel <david.vrabel@...rix.com>
Cc: Ian Campbell <ian.campbell@...rix.com>
Cc: <stable@...r.kernel.org>
---
 arch/x86/xen/Makefile  | 4 ++--
 arch/x86/xen/xen-ops.h | 7 ++-----
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index 7322755..4b6e29a 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -13,13 +13,13 @@ CFLAGS_mmu.o			:= $(nostackp)
 obj-y		:= enlighten.o setup.o multicalls.o mmu.o irq.o \
 			time.o xen-asm.o xen-asm_$(BITS).o \
 			grant-table.o suspend.o platform-pci-unplug.o \
-			p2m.o
+			p2m.o apic.o
 
 obj-$(CONFIG_EVENT_TRACING) += trace.o
 
 obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o
 obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
-obj-$(CONFIG_XEN_DOM0)		+= apic.o vga.o
+obj-$(CONFIG_XEN_DOM0)		+= vga.o
 obj-$(CONFIG_SWIOTLB_XEN)	+= pci-swiotlb-xen.o
 obj-$(CONFIG_XEN_EFI)		+= efi.o
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index c20fe29..d0a543b 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -98,20 +98,17 @@ static inline void xen_uninit_lock_cpu(int cpu)
 #endif
 
 struct dom0_vga_console_info;
-
 #ifdef CONFIG_XEN_DOM0
 void __init xen_init_vga(const struct dom0_vga_console_info *, size_t size);
-void __init xen_init_apic(void);
 #else
 static inline void __init xen_init_vga(const struct dom0_vga_console_info *info,
 				       size_t size)
 {
 }
-static inline void __init xen_init_apic(void)
-{
-}
 #endif
 
+void __init xen_init_apic(void);
+
 #ifdef CONFIG_XEN_EFI
 extern void xen_efi_init(void);
 #else
-- 
2.5.0

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