Re: [PATCH v1 19/24] vfio-user: secure DMA support

[John Johnson]

> On Dec 9, 2022, at 10:01 AM, John Levon  wrote:
> 
> On Tue, Nov 08, 2022 at 03:13:41PM -0800, John Johnson wrote:
> 
>> Secure DMA forces the remote process to use DMA r/w messages
>> instead of directly mapping guest memeory.
> 
> I don't really get why this is called "secure" - shouldn't have an option name
> more closely resembling what it actually does?
> 

The option was added to address a security concern if the server has
mmap() access to guest memory.  I can re-name it.

JJ

Re: [PATCH v1 19/24] vfio-user: secure DMA support

[John Levon]

On Tue, Nov 08, 2022 at 03:13:41PM -0800, John Johnson wrote:

> Secure DMA forces the remote process to use DMA r/w messages
> instead of directly mapping guest memeory.

I don't really get why this is called "secure" - shouldn't have an option name
more closely resembling what it actually does?

regards
john

[PATCH v1 19/24] vfio-user: secure DMA support

[John Johnson]

Secure DMA forces the remote process to use DMA r/w messages
instead of directly mapping guest memeory.

Signed-off-by: John G Johnson 
Signed-off-by: Elena Ufimtseva 
Signed-off-by: Jagannathan Raman 
---
 hw/vfio/pci.c  | 4 
 hw/vfio/pci.h  | 1 +
 hw/vfio/user.c | 2 +-
 hw/vfio/user.h | 1 +
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 53e3bb8..ce6776b 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3610,6 +3610,9 @@ static void vfio_user_pci_realize(PCIDevice *pdev, Error 
**errp)
 vbasedev->proxy = proxy;
 vfio_user_set_handler(vbasedev, vfio_user_pci_process_req, vdev);
 
+if (udev->secure_dma) {
+proxy->flags |= VFIO_PROXY_SECURE;
+}
 if (udev->send_queued) {
 proxy->flags |= VFIO_PROXY_FORCE_QUEUED;
 }
@@ -3718,6 +3721,7 @@ static void vfio_user_instance_finalize(Object *obj)
 
 static Property vfio_user_pci_dev_properties[] = {
 DEFINE_PROP_STRING("socket", VFIOUserPCIDevice, sock_name),
+DEFINE_PROP_BOOL("secure-dma", VFIOUserPCIDevice, secure_dma, false),
 DEFINE_PROP_BOOL("x-send-queued", VFIOUserPCIDevice, send_queued, false),
 DEFINE_PROP_BOOL("x-no-posted-writes", VFIOUserPCIDevice, no_post, false),
 DEFINE_PROP_END_OF_LIST(),
diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index c04fa58..c4b8e5c 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -196,6 +196,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(VFIOUserPCIDevice, VFIO_USER_PCI)
 struct VFIOUserPCIDevice {
 VFIOPCIDevice device;
 char *sock_name;
+bool secure_dma;/* disable shared mem for DMA */
 bool send_queued;   /* all sends are queued */
 bool no_post;   /* all regions write are sync */
 };
diff --git a/hw/vfio/user.c b/hw/vfio/user.c
index d62fe05..0c5493e 100644
--- a/hw/vfio/user.c
+++ b/hw/vfio/user.c
@@ -1627,7 +1627,7 @@ static int vfio_user_io_dma_map(VFIOContainer *container, 
MemoryRegion *mr,
  * map->vaddr enters as a QEMU process address
  * make it either a file offset for mapped areas or 0
  */
-if (fd != -1) {
+if (fd != -1 && (container->proxy->flags & VFIO_PROXY_SECURE) == 0) {
 void *addr = (void *)(uintptr_t)map->vaddr;
 
 map->vaddr = qemu_ram_block_host_offset(mr->ram_block, addr);
diff --git a/hw/vfio/user.h b/hw/vfio/user.h
index 19b8a29..6bd9fd3 100644
--- a/hw/vfio/user.h
+++ b/hw/vfio/user.h
@@ -83,6 +83,7 @@ typedef struct VFIOProxy {
 
 /* VFIOProxy flags */
 #define VFIO_PROXY_CLIENT0x1
+#define VFIO_PROXY_SECURE0x2
 #define VFIO_PROXY_FORCE_QUEUED  0x4
 #define VFIO_PROXY_NO_POST   0x8
 
-- 
1.8.3.1