linux-kernel - [PATCH] drivers/xen/xenbus: remove quirk for Xen 3.x

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Message-ID: <20250815074052.13792-1-jgross@suse.com>
Date: Fri, 15 Aug 2025 09:40:52 +0200
From: Juergen Gross <jgross@...e.com>
To: linux-kernel@...r.kernel.org
Cc: Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
	xen-devel@...ts.xenproject.org
Subject: [PATCH] drivers/xen/xenbus: remove quirk for Xen 3.x

The kernel is not supported to run as a Xen guest on Xen versions
older than 4.0.

Remove xen_strict_xenbus_quirk() which is testing the Xen version to be
at least 4.0.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
 drivers/xen/xenbus/xenbus_xs.c | 23 -----------------------
 1 file changed, 23 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 3c9da446b85d..528682bf0c7f 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -718,26 +718,6 @@ int xs_watch_msg(struct xs_watch_event *event)
 	return 0;
 }
 
-/*
- * Certain older XenBus toolstack cannot handle reading values that are
- * not populated. Some Xen 3.4 installation are incapable of doing this
- * so if we are running on anything older than 4 do not attempt to read
- * control/platform-feature-xs_reset_watches.
- */
-static bool xen_strict_xenbus_quirk(void)
-{
-#ifdef CONFIG_X86
-	uint32_t eax, ebx, ecx, edx, base;
-
-	base = xen_cpuid_base();
-	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
-
-	if ((eax >> 16) < 4)
-		return true;
-#endif
-	return false;
-
-}
 static void xs_reset_watches(void)
 {
 	int err;
@@ -745,9 +725,6 @@ static void xs_reset_watches(void)
 	if (!xen_hvm_domain() || xen_initial_domain())
 		return;
 
-	if (xen_strict_xenbus_quirk())
-		return;
-
 	if (!xenbus_read_unsigned("control",
 				  "platform-feature-xs_reset_watches", 0))
 		return;
-- 
2.43.0