From: Stephen C. Tweedie <sct@redhat.com>
Subject: [RHEL-5 Patch] Fix agp on x86_64 under Xen
Date: Tue, 19 Dec 2006 23:08:17 +0000
Bugzilla: 217715
Message-Id: <1166569697.6309.144.camel@sisko.scot.redhat.com>
Changelog: Xen: Fix agp on x86_64 under Xen


Hi all,

Fixes blocker bug 217715:

        https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=217715
        Bugzilla Bug 217715: dom0: panic w/X on i965 (appears to be
        agpgart?)

Brown-paper-bag bug time.  Xen has its own agp definitions in
include/asm-$ARCH/mach-xen/asm/agp.h, to cater for the difference
between logical and machine addresses when running virtualised.

Except --- whoops --- it only actually supplies that header file for
i386, not x86_64.  So use of AGP on x86_64 doesn't translate addresses,
and corrupts memory randomly.

Has been fixed upstream in changeset 12606:
        
        # HG changeset patch
        # User kfraser@localhost.localdomain
        # Date 1164907312 0
        # Node ID 2c5bed93ffbcc4585a5bdaf4c3224183735942eb
        # Parent  27a5a62552c039c2d35379095e04c41a0aa34991
        linux/x86-64: missing agp.h
        
        This causes data corruption and/or crashes when AGP is actually
        used.
        
        Signed-off-by: Jan Beulich <jbeulich@novell.com>
        
I've tested it on a local box with i965 graphics which would previously
crash randomly whenever X was used.  Has survived a dozen or so X
restarts over two reboots with the patch applied.

The attached patch is exactly equivalent to 

	cp include/asm-i386/mach-xen/asm/agp.h include/asm-x86_64/mach-xen/asm/

on our RHEL5 tree.  Will set a scratch build going to test compiles with
the full kernel config, I've only built it locally on a reduced config
so far.

Please ACK.

--Stephen


commit a489517739c9a8262746e1261b803376a1d129cd
Author: Stephen Tweedie <sct@redhat.com>

    Copy i386 agp.h to x86-64

diff --git a/include/asm-x86_64/mach-xen/asm/agp.h b/include/asm-x86_64/mach-xen/asm/agp.h
new file mode 100644
index 0000000..1389863
--- /dev/null
+++ b/include/asm-x86_64/mach-xen/asm/agp.h
@@ -0,0 +1,37 @@
+#ifndef AGP_H
+#define AGP_H 1
+
+#include <asm/pgtable.h>
+#include <asm/cacheflush.h>
+#include <asm/system.h>
+
+/* 
+ * Functions to keep the agpgart mappings coherent with the MMU.
+ * The GART gives the CPU a physical alias of pages in memory. The alias region is
+ * mapped uncacheable. Make sure there are no conflicting mappings
+ * with different cachability attributes for the same page. This avoids
+ * data corruption on some CPUs.
+ */
+
+int map_page_into_agp(struct page *page);
+int unmap_page_from_agp(struct page *page);
+#define flush_agp_mappings() global_flush_tlb()
+
+/* Could use CLFLUSH here if the cpu supports it. But then it would
+   need to be called for each cacheline of the whole page so it may not be 
+   worth it. Would need a page for it. */
+#define flush_agp_cache() wbinvd()
+
+/* Convert a physical address to an address suitable for the GART. */
+#define phys_to_gart(x) phys_to_machine(x)
+#define gart_to_phys(x) machine_to_phys(x)
+
+/* GATT allocation. Returns/accepts GATT kernel virtual address. */
+#define alloc_gatt_pages(order)	({                                          \
+	char *_t; dma_addr_t _d;                                            \
+	_t = dma_alloc_coherent(NULL,PAGE_SIZE<<(order),&_d,GFP_KERNEL);    \
+	_t; })
+#define free_gatt_pages(table, order)	\
+	dma_free_coherent(NULL,PAGE_SIZE<<(order),(table),virt_to_bus(table))
+
+#endif