This is purely for testing, to see if it works around a bug in i915. It
is not intended to be merged.
NOT-signed-off-by: DO NOT MERGE
---
xen/arch/x86/include/asm/page.h | 4 ++--
xen/arch/x86/include/asm/processor.h | 10 +++++-----
xen/arch/x86/mm.c | 8 --------
3 files changed, 7 insertions(+), 15 deletions(-)
diff --git a/xen/arch/x86/include/asm/page.h b/xen/arch/x86/include/asm/page.h
index
b585235d064a567082582c8e92a4e8283fd949ca..ab9b46f1d0901e50a83fd035ff28d1bda0b781a2
100644
--- a/xen/arch/x86/include/asm/page.h
+++ b/xen/arch/x86/include/asm/page.h
@@ -333,11 +333,11 @@ void efi_update_l4_pgtable(unsigned int l4idx,
l4_pgentry_t);
/* Memory types, encoded under Xen's choice of MSR_PAT. */
#define _PAGE_WB ( 0)
-#define _PAGE_WT ( _PAGE_PWT)
+#define _PAGE_WC ( _PAGE_PWT)
#define _PAGE_UCM ( _PAGE_PCD )
#define _PAGE_UC ( _PAGE_PCD | _PAGE_PWT)
-#define _PAGE_WC (_PAGE_PAT )
#define _PAGE_WP (_PAGE_PAT | _PAGE_PWT)
+#define _PAGE_WT (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)
/*
* Debug option: Ensure that granted mappings are not implicitly unmapped.
diff --git a/xen/arch/x86/include/asm/processor.h
b/xen/arch/x86/include/asm/processor.h
index
60b902060914584957db8afa5c7c1e6abdad4d13..3993d5638626f0948bb7ac8192d2eda187eb1bdb
100644
--- a/xen/arch/x86/include/asm/processor.h
+++ b/xen/arch/x86/include/asm/processor.h
@@ -94,16 +94,16 @@
/*
* Host IA32_CR_PAT value to cover all memory types. This is not the default
- * MSR_PAT value, and is an ABI with PV guests.
+ * MSR_PAT value, and is needed by the Linux i915 driver.
*/
#define XEN_MSR_PAT ((_AC(X86_MT_WB, ULL) << 0x00) | \
- (_AC(X86_MT_WT, ULL) << 0x08) | \
+ (_AC(X86_MT_WC, ULL) << 0x08) | \
(_AC(X86_MT_UCM, ULL) << 0x10) | \
(_AC(X86_MT_UC, ULL) << 0x18) | \
- (_AC(X86_MT_WC, ULL) << 0x20) | \
+ (_AC(X86_MT_WB, ULL) << 0x20) | \
(_AC(X86_MT_WP, ULL) << 0x28) | \
- (_AC(X86_MT_UC, ULL) << 0x30) | \
- (_AC(X86_MT_UC, ULL) << 0x38))
+ (_AC(X86_MT_UCM, ULL) << 0x30) | \
+ (_AC(X86_MT_WT, ULL) << 0x38))
#ifndef __ASSEMBLY__
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index
69ce597c7cd5283ae4b5f3bc0a6dfa0bb3228d3d..c536f7807a418c160366c22b6c4f937a5023f14b
100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -6387,14 +6387,6 @@ unsigned long get_upper_mfn_bound(void)
*/
static void __init __maybe_unused build_assertions(void)
{
- /*
- * If this trips, any guest that blindly rely on the public API in xen.h
- * (instead of reading the PAT from Xen, as Linux 3.19+ does) will be
- * broken. Furthermore, live migration of PV guests between Xen versions
- * using different PATs will not work.
- */
- BUILD_BUG_ON(XEN_MSR_PAT != 0x050100070406ULL);
-
/*
* _PAGE_WB must be zero for several reasons, not least because Linux
* assumes it.
--
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
