patch-0001-x86-mm-shadow-avoid-assuming-a-specific-Xen-PAT.patch

From cfee1577708bc765afef981bcc66ee09dd76a6a0 Mon Sep 17 00:00:00 2001
Message-Id: <cfee1577708bc765afef981bcc66ee09dd76a6a0.1671771766.git.demi@invisiblethingslab.com>
In-Reply-To: <cover.1671771766.git.demi@invisiblethingslab.com>
References: <cover.1671771766.git.demi@invisiblethingslab.com>
From: Demi Marie Obenour <demi@invisiblethingslab.com>
Date: Tue, 6 Dec 2022 13:54:33 +0100
Subject: [PATCH 01/10] x86/mm/shadow: avoid assuming a specific Xen PAT
Cc: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

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 99e410d999455d544a89a946d1df3bb42c364f12..95ff6df5d91e1bcfe6c88a565d61b5c69ff1538f 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -667,8 +667,8 @@ _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