linux-kernel - [PATCH] x86/xen: set default memory type for pv guests to WB

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Date:   Thu, 15 Jun 2023 14:39:59 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, xen-devel@...ts.xenproject.org
Subject: [PATCH] x86/xen: set default memory type for pv guests to WB

When running as an unprivileged PV-guest under Xen (not dom0), the
default MTRR memory type should be write-back.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
Based on tip x86/mtrr branch
---
 arch/x86/xen/enlighten_pv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 8732b85d5650..93b658248d01 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -187,6 +187,8 @@ static void __init xen_pv_init_platform(void)
 
 	if (xen_initial_domain())
 		xen_set_mtrr_data();
+	else
+		mtrr_overwrite_state(NULL, 0, MTRR_TYPE_WRBACK);
 }
 
 static void __init xen_pv_guest_late_init(void)
-- 
2.35.3