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[Xen-devel] [PATCH 04/17] xen: create dummy ioapic mapping

To: Ingo Molnar <mingo@xxxxxxx>
Subject: [Xen-devel] [PATCH 04/17] xen: create dummy ioapic mapping
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 27 May 2009 00:37:17 -0700
Cc: Chris Wright <chrisw@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ky Srinivasan <ksrinivasan@xxxxxxxxxx>, kurt.hackel@xxxxxxxxxx, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, Jens Axboe <jens.axboe@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Greg KH <gregkh@xxxxxxx>
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We don't allow direct access to the IO apic, so make sure that any
request to map it just "maps" non-present pages.  We should see any
attempts at direct access explode nicely.

[ Impact: debuggability (make failures obvious) ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 331e52d..139c8de 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1919,6 +1919,16 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t 
phys, pgprot_t prot)
                pte = pfn_pte(phys, prot);
                break;
 
+#ifdef CONFIG_X86_IO_APIC
+       case FIX_IO_APIC_BASE_0 ... FIX_IO_APIC_BASE_END:
+               /*
+                * We just don't map the IO APIC - all access is via
+                * hypercalls.  Keep the address in the pte for reference.
+                */
+               pte = pfn_pte(phys, PAGE_NONE);
+               break;
+#endif
+
        case FIX_PARAVIRT_BOOTMAP:
                /* This is an MFN, but it isn't an IO mapping from the
                   IO domain */
-- 
1.6.0.6


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