[PATCH v3] vhost: disable for OABI

[Michael S. Tsirkin]

vhost is currently broken on the some ARM configs.

The reason is that that uses apcs-gnu which is the ancient OABI that is been
deprecated for a long time.

Given that virtio support on such ancient systems is not needed in the
first place, let's just add something along the lines of

	depends on !ARM || AEABI

to the virtio Kconfig declaration, and add a comment that it has to do
with struct member alignment.

Note: we can't make VHOST and VHOST_RING themselves have
a dependency since these are selected. Add a new symbol for that.

Link: https://lore.kernel.org/r/20200406121233.109889-3-mst@xxxxxxxxxx
Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Suggested-by: Richard Earnshaw <Richard.Earnshaw@xxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---

Changes from v2:
	- drop prompt from VHOST_DPN
	- typo fix in commit log
	- OABI is a possible ARM config but not the default one

 drivers/misc/mic/Kconfig |  2 +-
 drivers/net/caif/Kconfig |  2 +-
 drivers/vdpa/Kconfig     |  2 +-
 drivers/vhost/Kconfig    | 17 +++++++++++++----
 4 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/mic/Kconfig b/drivers/misc/mic/Kconfig
index 8f201d019f5a..3bfe72c59864 100644
--- a/drivers/misc/mic/Kconfig
+++ b/drivers/misc/mic/Kconfig
@@ -116,7 +116,7 @@ config MIC_COSM
 
 config VOP
 	tristate "VOP Driver"
-	depends on VOP_BUS
+	depends on VOP_BUS && VHOST_DPN
 	select VHOST_RING
 	select VIRTIO
 	help
diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
index 9db0570c5beb..661c25eb1c46 100644
--- a/drivers/net/caif/Kconfig
+++ b/drivers/net/caif/Kconfig
@@ -50,7 +50,7 @@ config CAIF_HSI
 
 config CAIF_VIRTIO
 	tristate "CAIF virtio transport driver"
-	depends on CAIF && HAS_DMA
+	depends on CAIF && HAS_DMA && VHOST_DPN
 	select VHOST_RING
 	select VIRTIO
 	select GENERIC_ALLOCATOR
diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
index 71d9a64f2c7d..ee35f8261a88 100644
--- a/drivers/vdpa/Kconfig
+++ b/drivers/vdpa/Kconfig
@@ -10,7 +10,7 @@ if VDPA
 
 config VDPA_SIM
 	tristate "vDPA device simulator"
-	depends on RUNTIME_TESTING_MENU && HAS_DMA
+	depends on RUNTIME_TESTING_MENU && HAS_DMA && VHOST_DPN
 	select VHOST_RING
 	select VHOST_IOTLB
 	default n
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index e79cbbdfea45..d9b3a3ec765a 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -12,6 +12,15 @@ config VHOST_RING
 	  This option is selected by any driver which needs to access
 	  the host side of a virtio ring.
 
+config VHOST_DPN
+	bool
+	depends on !ARM || AEABI
+	default y
+	help
+	  Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
+	  This excludes the deprecated ARM ABI since that forces a 4 byte
+	  alignment on all structs - incompatible with virtio spec requirements.
+
 config VHOST
 	tristate
 	select VHOST_IOTLB
@@ -27,7 +36,7 @@ if VHOST_MENU
 
 config VHOST_NET
 	tristate "Host kernel accelerator for virtio net"
-	depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
+	depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP) && VHOST_DPN
 	select VHOST
 	---help---
 	  This kernel module can be loaded in host kernel to accelerate
@@ -39,7 +48,7 @@ config VHOST_NET
 
 config VHOST_SCSI
 	tristate "VHOST_SCSI TCM fabric driver"
-	depends on TARGET_CORE && EVENTFD
+	depends on TARGET_CORE && EVENTFD && VHOST_DPN
 	select VHOST
 	default n
 	---help---
@@ -48,7 +57,7 @@ config VHOST_SCSI
 
 config VHOST_VSOCK
 	tristate "vhost virtio-vsock driver"
-	depends on VSOCKETS && EVENTFD
+	depends on VSOCKETS && EVENTFD && VHOST_DPN
 	select VHOST
 	select VIRTIO_VSOCKETS_COMMON
 	default n
@@ -62,7 +71,7 @@ config VHOST_VSOCK
 
 config VHOST_VDPA
 	tristate "Vhost driver for vDPA-based backend"
-	depends on EVENTFD
+	depends on EVENTFD && VHOST_DPN
 	select VHOST
 	depends on VDPA
 	help
-- 
MST