[PATCH 6/8] x86: Derive XEN_MSR_PAT from its individual entries

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

This avoids it being a magic constant that is difficult for humans to
decode.  Use a _Static_assert to check that the old and new values are
identical.

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/include/asm/processor.h | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/include/asm/processor.h 
b/xen/arch/x86/include/asm/processor.h
index 
8e2816fae9b97bd4e153a30cc3802971fe0355af..64b75e444947c64e2e5eba457deec92a873d7a63
 100644
--- a/xen/arch/x86/include/asm/processor.h
+++ b/xen/arch/x86/include/asm/processor.h
@@ -92,13 +92,33 @@
                           X86_EFLAGS_NT|X86_EFLAGS_DF|X86_EFLAGS_IF|    \
                           X86_EFLAGS_TF)
 
+/* Individual entries in IA32_CR_PAT */
+#define MSR_PAT_UC  _AC(0x00, ULL)
+#define MSR_PAT_WC  _AC(0x01, ULL)
+#define MSR_PAT_RESERVED_1  _AC(0x02, ULL)
+#define MSR_PAT_RESERVED_2  _AC(0x03, ULL)
+#define MSR_PAT_WT  _AC(0x04, ULL)
+#define MSR_PAT_WP  _AC(0x05, ULL)
+#define MSR_PAT_WB  _AC(0x06, ULL)
+#define MSR_PAT_UCM _AC(0x07, ULL)
+
 /*
  * 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.
  */
-#define XEN_MSR_PAT _AC(0x050100070406, ULL)
+#define XEN_MSR_PAT (MSR_PAT_WB  << 0x00 | \
+                     MSR_PAT_WT  << 0x08 | \
+                     MSR_PAT_UCM << 0x10 | \
+                     MSR_PAT_UC  << 0x18 | \
+                     MSR_PAT_WC  << 0x20 | \
+                     MSR_PAT_WP  << 0x28 | \
+                     MSR_PAT_UC  << 0x30 | \
+                     MSR_PAT_UC  << 0x38 | \
+                     0)
 
 #ifndef __ASSEMBLY__
+_Static_assert(XEN_MSR_PAT == 0x050100070406ULL,
+               "wrong XEN_MSR_PAT breaks PV guests");
 
 struct domain;
 struct vcpu;
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab