[PATCH 10/11] xen/arm: device assignment on 1:1 direct-map domain

From: Penny Zheng <penny.zheng@arm.com>
To: <xen-devel@lists.xenproject.org>, <sstabellini@kernel.org>,
	<julien@xen.org>
Cc: <Bertrand.Marquis@arm.com>, <Penny.Zheng@arm.com>, <Wei.Chen@arm.com>
Subject: [PATCH 10/11] xen/arm: device assignment on 1:1 direct-map domain
Date: Thu, 23 Sep 2021 03:11:14 +0000	[thread overview]
Message-ID: <20210923031115.1429719-11-penny.zheng@arm.com> (raw)
In-Reply-To: <20210923031115.1429719-1-penny.zheng@arm.com>

User could do device passthrough, with "xen,force-assign-without-iommu" in
the device tree snippet, on trusted guest through 1:1 direct-map,
if IOMMU absent or disabled on hardware.

In order to achieve that, this patch adds 1:1 direct-map check and disables
iommu-related action.

Signed-off-by: Penny Zheng <penny.zheng@arm.com>
---
 xen/arch/arm/domain_build.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index c92e510ae7..9a9d2522b7 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2070,14 +2070,18 @@ static int __init handle_passthrough_prop(struct kernel_info *kinfo,
     if ( res < 0 )
         return res;
 
+    /*
+     * If xen_force, we allow assignment of devices without IOMMU protection.
+     * And if IOMMU is disabled or absent, 1:1 direct-map is necessary
+     */
+    if ( xen_force && is_domain_direct_mapped(kinfo->d) &&
+         !dt_device_is_protected(node) )
+        return 0;
+
     res = iommu_add_dt_device(node);
     if ( res < 0 )
         return res;
 
-    /* If xen_force, we allow assignment of devices without IOMMU protection. */
-    if ( xen_force && !dt_device_is_protected(node) )
-        return 0;
-
     return iommu_assign_dt_device(kinfo->d, node);
 }
 
-- 
2.25.1


