linux-kernel - [PATCH V2 7/7] arm/xen: Assign xen-grant DMA ops for xen-grant DMA devices

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Message-Id: <1651947548-4055-8-git-send-email-olekstysh@gmail.com>
Date:   Sat,  7 May 2022 21:19:08 +0300
From:   Oleksandr Tyshchenko <olekstysh@...il.com>
To:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Julien Grall <julien@....org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Christoph Hellwig <hch@...radead.org>
Subject: [PATCH V2 7/7] arm/xen: Assign xen-grant DMA ops for xen-grant DMA devices

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>

By assigning xen-grant DMA ops we will restrict memory access for
passed device using Xen grant mappings. This is needed for using any
virtualized device (e.g. virtio) in Xen guests in a safe manner.

Please note, for the virtio devices the XEN_VIRTIO config should
be enabled (it forces ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS).

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Reviewed-by: Stefano Stabellini <sstabellini@...nel.org>
---
Changes RFC -> V1:
   - update commit subject/description
   - remove #ifdef CONFIG_XEN_VIRTIO
   - re-organize the check taking into the account that
     swiotlb and virtio cases are mutually exclusive
   - update according to the new naming scheme:
     s/virtio/grant_dma

Changes V1 -> V2:
   - add Stefano's R-b
   - remove arch_has_restricted_virtio_memory_access() check
   - update commit description
   - remove the inclusion of virtio_config.h
---
 include/xen/arm/xen-ops.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/xen/arm/xen-ops.h b/include/xen/arm/xen-ops.h
index 288deb1..b0766a6 100644
--- a/include/xen/arm/xen-ops.h
+++ b/include/xen/arm/xen-ops.h
@@ -3,11 +3,14 @@
 #define _ASM_ARM_XEN_OPS_H
 
 #include <xen/swiotlb-xen.h>
+#include <xen/xen-ops.h>
 
 static inline void xen_setup_dma_ops(struct device *dev)
 {
 #ifdef CONFIG_XEN
-	if (xen_swiotlb_detect())
+	if (xen_is_grant_dma_device(dev))
+		xen_grant_setup_dma_ops(dev);
+	else if (xen_swiotlb_detect())
 		dev->dma_ops = &xen_swiotlb_dma_ops;
 #endif
 }
-- 
2.7.4