Mailing List Archive

commit 4b40d68e663e87eb916b5bdf3da9743a17f43537
Author: Demi Marie Obenour <demi@invisiblethingslab.com>
AuthorDate: Tue Dec 20 16:51:55 2022 +0100
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Tue Dec 20 16:51:55 2022 +0100

x86: derive XEN_MSR_PAT from its individual entries

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

Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
xen/arch/x86/include/asm/processor.h | 9 ++++++++-
xen/arch/x86/mm.c | 11 +++++++++++
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/include/asm/processor.h b/xen/arch/x86/include/asm/processor.h
index 8e2816fae9..60b9020609 100644
--- a/xen/arch/x86/include/asm/processor.h
+++ b/xen/arch/x86/include/asm/processor.h
@@ -96,7 +96,14 @@
* 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 ((_AC(X86_MT_WB, ULL) << 0x00) | \
+ (_AC(X86_MT_WT, ULL) << 0x08) | \
+ (_AC(X86_MT_UCM, ULL) << 0x10) | \
+ (_AC(X86_MT_UC, ULL) << 0x18) | \
+ (_AC(X86_MT_WC, ULL) << 0x20) | \
+ (_AC(X86_MT_WP, ULL) << 0x28) | \
+ (_AC(X86_MT_UC, ULL) << 0x30) | \
+ (_AC(X86_MT_UC, ULL) << 0x38))

#ifndef __ASSEMBLY__

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 8b9740f575..8fa29d5c8b 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -6283,6 +6283,17 @@ unsigned long get_upper_mfn_bound(void)
return min(max_mfn, 1UL << (paddr_bits - PAGE_SHIFT)) - 1;
}

+static void __init __maybe_unused build_assertions(void)
+{
+ /*
+ * If this trips, any guests 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);
+}
+
/*
* Local variables:
* mode: C
--
generated by git-patchbot for /home/xen/git/xen.git#master