Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Juergen Gross <jgross@suse.com>
To:     xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Cc:     Juergen Gross <jgross@suse.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH 1/3] xen: check required Xen features
Date:   Thu, 22 Apr 2021 17:10:05 +0200
Message-Id: <20210422151007.2205-2-jgross@suse.com>
In-Reply-To: <20210422151007.2205-1-jgross@suse.com>
References: <20210422151007.2205-1-jgross@suse.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Linux kernel is not supported to run on Xen versions older than 4.0.

Add tests for required Xen features always being present in Xen 4.0
and newer.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/xen/features.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/xen/features.c b/drivers/xen/features.c
index 25c053b09605..60503299c9bc 100644
--- a/drivers/xen/features.c
+++ b/drivers/xen/features.c
@@ -9,13 +9,26 @@
 #include <linux/types.h>
 #include <linux/cache.h>
 #include <linux/export.h>
+#include <linux/printk.h>
 
 #include <asm/xen/hypercall.h>
 
+#include <xen/xen.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/version.h>
 #include <xen/features.h>
 
+/*
+ * Linux kernel expects at least Xen 4.0.
+ *
+ * Assume some features to be available for that reason (depending on guest
+ * mode, of course).
+ */
+#define chk_feature(f) {						\
+		if (!xen_feature(f))					\
+			pr_err("Xen: feature %s not available!\n", #f);	\
+	}
+
 u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
 EXPORT_SYMBOL_GPL(xen_features);
 
@@ -31,4 +44,9 @@ void xen_setup_features(void)
 		for (j = 0; j < 32; j++)
 			xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
 	}
+
+	if (xen_pv_domain()) {
+		chk_feature(XENFEAT_mmu_pt_update_preserve_ad);
+		chk_feature(XENFEAT_gnttab_map_avail_bits);
+	}
 }
-- 
2.26.2