linux-kernel - [PATCH] x86/CPU/AMD: avoid printing reset reasons on Xen domU

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Message-ID: <20251219010131.12659-1-ariadne@ariadne.space>
Date: Thu, 18 Dec 2025 17:01:31 -0800
From: Ariadne Conill <ariadne@...adne.space>
To: linux-kernel@...r.kernel.org
Cc: mario.limonciello@....com,
	darwi@...utronix.de,
	sandipan.das@....com,
	kai.huang@...el.com,
	me@...aill.net,
	yazen.ghannam@....com,
	riel@...riel.com,
	peterz@...radead.org,
	hpa@...or.com,
	x86@...nel.org,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	Ariadne Conill <ariadne@...adne.space>,
	xen-devel@...ts.xenproject.org,
	stable@...r.kernel.org
Subject: [PATCH] x86/CPU/AMD: avoid printing reset reasons on Xen domU

Xen domU cannot access the given MMIO address for security reasons,
resulting in a failed hypercall in ioremap() due to permissions.

Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset")
Signed-off-by: Ariadne Conill <ariadne@...adne.space>
Cc: xen-devel@...ts.xenproject.org
Cc: stable@...r.kernel.org
---
 arch/x86/kernel/cpu/amd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index a6f88ca1a6b4..99308fba4d7d 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -29,6 +29,8 @@
 # include <asm/mmconfig.h>
 #endif
 
+#include <xen/xen.h>
+
 #include "cpu.h"
 
 u16 invlpgb_count_max __ro_after_init = 1;
@@ -1333,6 +1335,10 @@ static __init int print_s5_reset_status_mmio(void)
 	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
 		return 0;
 
+	/* Xen PV domU cannot access hardware directly, so bail for domU case */
+	if (cpu_feature_enabled(X86_FEATURE_XENPV) && !xen_initial_domain())
+		return 0;
+
 	addr = ioremap(FCH_PM_BASE + FCH_PM_S5_RESET_STATUS, sizeof(value));
 	if (!addr)
 		return 0;
-- 
2.51.0