linux-kernel - [PATCH 12 of 38] xen/dom0: handle acpi lapic parsing in Xen dom0

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Date:	Thu, 13 Nov 2008 11:10:10 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Xen-devel <xen-devel@...ts.xensource.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Ian Campbell <ian.campbell@...rix.com>
Subject: [PATCH 12 of 38] xen/dom0: handle acpi lapic parsing in Xen dom0

When running in Xen dom0, we still want to parse the ACPI tables to
find out about local and IO apics, but we don't want to actually use
the lapics.

Put a couple of tests for Xen to prevent lapics from being mapped or
accessed.  This is very Xen-specific behaviour, so there didn't seem to
be any point in adding more indirection.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/include/asm/xen/hypervisor.h |    2 ++
 arch/x86/kernel/acpi/boot.c           |   10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -46,6 +46,8 @@
 extern enum xen_domain_type xen_domain_type;
 
 #ifdef CONFIG_XEN
+#include <xen/interface/xen.h>
+
 #define xen_domain()		(xen_domain_type != XEN_NATIVE)
 #else
 #define xen_domain()		(0)
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -42,6 +42,8 @@
 #include <asm/mpspec.h>
 #include <asm/smp.h>
 
+#include <asm/xen/hypervisor.h>
+
 #ifdef CONFIG_X86_LOCAL_APIC
 # include <mach_apic.h>
 #endif
@@ -234,6 +236,10 @@
 {
 	unsigned int ver = 0;
 
+	/* We don't want to register lapics when in Xen dom0 */
+	if (xen_initial_domain())
+		return;
+
 	if (!enabled) {
 		++disabled_cpus;
 		return;
@@ -755,6 +761,10 @@
 
 static void __init acpi_register_lapic_address(unsigned long address)
 {
+	/* Xen dom0 doesn't have usable lapics */
+	if (xen_initial_domain())
+		return;
+
 	mp_lapic_addr = address;
 
 	set_fixmap_nocache(FIX_APIC_BASE, address);


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