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d085eb8ce7
vhost is currently broken on the some ARM configs.
The reason is that the ring element addresses are passed between
components with different alignments assumptions. Thus, if
guest selects a pointer and host then gets and dereferences
it, then alignment assumed by the host's compiler might be
greater than the actual alignment of the pointer.
compiler on the host from assuming pointer is aligned.
This actually triggers on ARM with -mabi=apcs-gnu - which is a
deprecated configuration. With this OABI, compiler assumes that
all structures are 4 byte aligned - which is stronger than
virtio guarantees for available and used rings, which are
merely 2 bytes. Thus a guest without -mabi=apcs-gnu running
on top of host with -mabi=apcs-gnu will be broken.
The correct fix is to force alignment of structures - however
that is an intrusive fix that's best deferred until the next release.
We didn't previously support such ancient systems at all - this surfaced
after vdpa support prompted removing dependency of vhost on
VIRTULIZATION. So for now, 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.
We should be able to drop this dependency down the road.
Fixes: 20c384f1ea ("vhost: refine vhost and vringh kconfig")
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Suggested-by: Richard Earnshaw <Richard.Earnshaw@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
32 lines
828 B
Plaintext
32 lines
828 B
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menuconfig VDPA
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tristate "vDPA drivers"
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help
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Enable this module to support vDPA device that uses a
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datapath which complies with virtio specifications with
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vendor specific control path.
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if VDPA
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config VDPA_SIM
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tristate "vDPA device simulator"
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depends on RUNTIME_TESTING_MENU && HAS_DMA && VHOST_DPN
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select VHOST_RING
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default n
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help
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vDPA networking device simulator which loop TX traffic back
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to RX. This device is used for testing, prototyping and
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development of vDPA.
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config IFCVF
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tristate "Intel IFC VF vDPA driver"
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depends on PCI_MSI
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default n
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help
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This kernel module can drive Intel IFC VF NIC to offload
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virtio dataplane traffic to hardware.
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To compile this driver as a module, choose M here: the module will
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be called ifcvf.
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endif # VDPA
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