0301-x86-mm-shadow-avoid-assuming-a-specific-Xen-PAT.patch

From 53ba5e1b48a538c366e4621634b493f4585bcac0 Mon Sep 17 00:00:00 2001
From: Demi Marie Obenour <demi@invisiblethingslab.com>
Date: Tue, 6 Dec 2022 13:54:33 +0100
Subject: [PATCH 1/9] x86/mm/shadow: avoid assuming a specific Xen PAT
To: xen-devel@lists.xenproject.org
Cc: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>,
    Jan Beulich <jbeulich@suse.com>,
    Andrew Cooper <andrew.cooper3@citrix.com>,
    "Roger Pau Monné" <roger.pau@citrix.com>,
    Wei Liu <wl@xen.org>,
    Jun Nakajima <jun.nakajima@intel.com>,
    Kevin Tian <kevin.tian@intel.com>,
    George Dunlap <george.dunlap@citrix.com>,
    Tim Deegan <tim@xen.org>

This makes the code easier to understand and more robust if Xen's PAT
ever changes.

Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/mm/shadow/multi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 2370b3060285fee895f335f2a82d3d22ca5d31ed..4e94fec3d50cde0e5a26ecb62ff4d00dd00f759d 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -629,8 +629,8 @@ _sh_propagate(struct vcpu *v,
     else if ( p2mt == p2m_mmio_direct &&
               rangeset_contains_singleton(mmio_ro_ranges, mfn_x(target_mfn)) )
     {
-        sflags &= ~(_PAGE_RW | _PAGE_PAT);
-        sflags |= _PAGE_PCD | _PAGE_PWT;
+        sflags &= ~(_PAGE_RW | PAGE_CACHE_ATTRS);
+        sflags |= _PAGE_UC;
     }
 
     // protect guest page tables
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab