The current PciRoot is only workable for the legacy I/O port 0xCF8
access mechanism; factor out the config access mechanism part of PciRoot
into PciConfigIo so that we can add a MMIO-based access mechanism for
ARM.
Change-Id: I87756b0ab31070d8717c76d419957bf5ea5d75ad
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1241539
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Most of PCI configuration space should be read only; initialize the
writable_bits field accordingly.
Change-Id: I67f93d81cfbac6000db51663bdf76e54aeac08f3
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1240659
Reviewed-by: Dylan Reid <dgreid@chromium.org>
The add_capability() function was using the normal PCI configuration
write_byte() function, which enforces read-only regions. This won't
work once the appropriate regions of config space are marked as read
only in the following commit, so add an internal-only helper function to
access bytes without applying writable_bits.
Change-Id: If61f79cd80950bf517d69c18aaf98c2e76841a56
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1240658
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Return the BAR number rather than the register offset within PCI config
space.
Change-Id: I6e965c5fe7218abe6986b461731f18abb34894c1
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1240653
Reviewed-by: Dylan Reid <dgreid@chromium.org>
VirtioDevices and potentially others need to register ioeventfds that
will be triggered when guests write to certain addresses. Allow
PciDevices to return an array of ioeventfds that the VM can install.
Change-Id: I2524c4e8c04f75a8d7868cac998304aecbb29c40
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1237360
Commit-Ready: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: Daniel Verkamp <dverkamp@chromium.org>
PciDevice implementations will have file descriptors that need to be
preserved across the minijail fork.
Change-Id: I0b1f5b827b55c4d8960ffa95331b82f9c692f304
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1237359
Reviewed-by: Dylan Reid <dgreid@chromium.org>
PCI class codes are made up of three fields: class, subclass, and
programming interface. Some class/subclass combinations do not define
any programming interfaces, so add an optional parameter to specify the
value and use 0 if it is not provided.
Change-Id: Ib4000eafe2d7d003ed5753d7b0ea05e16fd06130
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1237358
Reviewed-by: Dylan Reid <dgreid@chromium.org>
passing everything in to the pci code is getting annoying. Instead build
it up in arch which already has access to all the needed resources.
Change-Id: If42f994443c4f11152fca8da16f27fa4cd80580d
Reviewed-on: https://chromium-review.googlesource.com/1237357
Commit-Ready: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Rather than querying the flush timerfd state repeatedly on every write,
just track the state in a variable. This avoids an extra
timerfd_gettime() syscall on every write.
BUG=None
TEST=Verify that the flush timer still fires via strace
Change-Id: I5437d26570de466f05b496d3e0dce08a521c4fde
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1247443
Reviewed-by: Dylan Reid <dgreid@chromium.org>
To fully meet the requirements laid out by the virtio specification, we
need to fail write commands for devices that expose VIRTIO_BLK_F_RO with
a specific error code of VIRTIO_BLK_S_IOERR. Pipe the read_only status
down into the worker and the request execute function so that it can be
checked and return the correct error code.
BUG=chromium:872973
TEST=Attempt to write to read-only /dev/vda in termina
Change-Id: I98c8ad17fde497e5a529d9e65096fb4ef022fd65
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1211062
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Otherwise, the flush timer case of the PollContext continues to fire
repeatedly, since the timerfd remains readable.
BUG=None
TEST=Verify that crosvm virtio_blk thread no longer pins the CPU after
writes are done
Change-Id: I693346c078e07b97e30083f34d00be75fa93841d
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1232295
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
The Scm object was made to reduce the number of heap allocations in
the hot paths of poll loops, at the cost of some code complexity. As it
turns out, the number of file descriptors being sent or received is
usually just one or limited to a fixed amount that can easily be covered
with a fixed size stack allocated buffer.
This change implements that solution, with heap allocation as a backup
in the rare case that many file descriptors must be sent or received.
This change also moves the msg and cmsg manipulation code out of C and
into pure Rust. The move was necessary to allocate the correct amount
of buffer space at compile time. It also improves safety by reducing the
scope of unsafe code. Deleting the code for building the C library is
also a nice bonus.
Finally, the removal of the commonly used Scm struct required
transitioning existing usage to the ScmSocket trait based methods. This
includes all those changes.
TEST=cargo test
BUG=None
Change-Id: If27ba297f5416dd9b8bc686ce740866912fa0aa0
Reviewed-on: https://chromium-review.googlesource.com/1186146
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
If the guest doesn't issue a flush command after a write, insert one.
This will mainly help qcow backed files. However, it is a good idea for
block devices as well, it narrows the window for data loss.
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Change-Id: I1d6eaeda6fd5038ec994ed882e870ae025e3c151
Reviewed-on: https://chromium-review.googlesource.com/1211126
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Sandboxing only works when started as chronos via concierge client. If
started directly via crosvm as root, the jail will not have proper group
permissions to access the Wayland socket.
BUG=chromium:837073
TEST=build with --features=gpu; null_platform_test without --disable-sandbox
CQ-DEPEND=CL:1213779
Change-Id: I6331f7ae1f5b99d31ad44cf158f72337294771f0
Reviewed-on: https://chromium-review.googlesource.com/1181168
Commit-Ready: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
The virtio PCI specification places requirements on the PCI subsystem
IDs, so allow PCI devices to specify them in PciConfiguration.
Change-Id: I70bc6ad4333ba3601db2831fef03483bcaea70ff
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1208156
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
The status register is actually the high 16 bits of register index
STATUS_REG (1). Adjust the STATUS_REG_CAPABILITIES_USED_MASK value
accordingly so it is bit 4 within the high 16 bits.
Change-Id: I3fb695a577bae754eda5640224ef335c44b119eb
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1208152
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Currently VirtioDevice was only used by MmioDevice. Move it to a
separate file to allow it to be used by a PCI implementation in the
following commits.
Change-Id: Ie2de92d8876fdaa31d71341714681212d52a618c
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1208690
Commit-Ready: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Discard and Write Zeroes commands have been added to the virtio block
specification:
88c8553838
Implement both commands using the WriteZeroes trait.
BUG=chromium:850998
TEST=fstrim within termina on a writable qcow image
Change-Id: I33e54e303202328c10f7f2d6e69ab19f419f3998
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1188680
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Also fix the misleading add_capability() comment. The standard PCI
capability header is just two bytes (capability type and next pointer);
the length byte is only part of the vendor-specific capability (09h).
More importantly, the current implementation of add_capability() already
inserts the two-byte standard header, so the caller should not provide
it as part of cap_data.
BUG=None
TEST=cargo test -p devices
Change-Id: Id3517d021bfe29d08ff664d66455b15cf07af1d1
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1197069
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
The virtio 1.0 feature flag is defined as a shift count, not a mask.
While we're at it, change the virtio gpu features() function to the
avail_features style used in other devices for consistency.
BUG=None
TEST=None
Change-Id: I704d9676cfe5f13d9a2f83eb9160937e94070d1e
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1198224
Reviewed-by: Zach Reizner <zachr@chromium.org>
Define a struct to represent the virtio block configuration as defined
in the current revision of the specification. Only the capacity field
is set; all other fields are defaulted to 0, which should be safe, since
they are all controlled by feature flags that our device does not
advertise.
This is prep work for adding discard/write zeroes support to the block
device, since these commands require additional config fields that will
be added at the end of the config struct.
BUG=chromium:850998
TEST=cargo test -p devices; verify that container still boots and
reports the correct size
Change-Id: I8beb76195e446eb3dcbf1a99cc246ddd8cc8a7df
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1175235
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
The virtio block specification defines the VIRTIO_BLK_F_RO feature bit
to indicate read-only block devices. Plumb the read-only status of
block devices from the crosvm frontend into the virtio block device and
populate the flag when appropriate.
BUG=chromium:872973
TEST=Verify lsblk output in guest has the correct RO values
Change-Id: I23af87cce8020641cd702adca6e8ff9fdd2b8220
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1170306
Reviewed-by: Zach Reizner <zachr@chromium.org>
This matches other virtio device models (net, p9, vsock) and makes it
easier to add flags conditionally at device creation time.
BUG=chromium:872973
TEST=cargo test -p devices
Change-Id: I65b3f37c220fae44a3f6b397acc6c0eec2b70bf2
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1170305
Reviewed-by: Zach Reizner <zachr@chromium.org>
Convert the definition of VIRTIO_BLK_F_FLUSH to a shift count instead of
a bitmask. This matches the way the features are defined in the virtio
spec and makes block consistent with other device models, such as p9.
BUG=chromium:872973
TEST=cargo test -p devices
Change-Id: Iece974c6f4d826b7bb76622973f08469a7936234
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1170303
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Implement a new virtio_9p device to be used for sharing directories with
the VM.
BUG=chromium:703939
TEST=mount inside a VM and run `bonnie++ -r 256`
Append the shared directory to the crosvm command line:
--shared-dir /path/to/dir:test_9p
Then mount in the guest:
mkdir /tmp/9p
mount -t 9p -o trans=virtio test_9p /tmp/9p -oversion=9p2000.L
Or for a 9p root:
run --shared-dir /mnt/vm_root:/dev/root -p 'root=/dev/root ro rootflags=ro,trans=virtio,version=9p2000.L,cache=loose rootfstype=9p' vmlinux.bin
CQ-DEPEND=CL:1065170
Change-Id: I41fc21306ab5fa318a271f172d7057b767b29f31
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1065173
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Ensure eglImage is not destroyed until the referencing resource is dropped.
BUG=None
TEST=build with --features=gpu; null_platform_test
Change-Id: I55c33344f46b08f846e094451516fcd16c9d16ae
Reviewed-on: https://chromium-review.googlesource.com/1073958
Commit-Ready: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
In preparation of adding fence support, allow process_descriptor to
defer returning the descriptor until later by returning None.
BUG=None
TEST=build with --features=gpu; null_platform_test
Change-Id: I57e4dc438e7f5a925c870e0bd596f89a2ed4e083
Reviewed-on: https://chromium-review.googlesource.com/1073957
Commit-Ready: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Reviewed-by: David Riley <davidriley@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Add serial bus subclass
BUG=chromium:831850
TEST=cargo test
Change-Id: Iffd7a27b5cb423c928f0108b16fb58558cf7bcd4
Reviewed-on: https://chromium-review.googlesource.com/1152212
Commit-Ready: Jingkui Wang <jkwang@google.com>
Tested-by: Jingkui Wang <jkwang@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Implement a policy for the balloon device so that it starts taking
memory away from the VM when the system is under low memory conditions.
There are a few pieces here:
* Change the madvise call in MemoryMapping::dont_need_range to use
MADV_REMOVE instead of MADV_DONTNEED. The latter does nothing when
the memory mapping is shared across multiple processes while the
former immediately gives the pages in the specified range back to the
kernel. Subsequent accesses to memory in that range returns zero
pages.
* Change the protocol between the balloon device process and the main
crosvm process. Previously, the device process expected the main
process to send it increments in the amount of memory consumed by the
balloon device. Now, it instead just expects the absolute value of
the memory that should be consumed. To properly implement the policy
the main process needs to keep track of the total memory consumed by
the balloon device so this makes it easier to handle all the policy in
one place.
* Add a policy for dealing with low memory situations. When the VM
starts up, we determine the maximum amount of memory that the balloon
device should consume:
* If the VM has more than 1.5GB of memory, the balloon device max is
the size of the VM memory minus 1GB.
* Otherwise, if the VM has at least 500MB, the balloon device max is
50% of the size of the VM memory.
* Otherwise, the max is 0.
The increment used to change the size of the balloon is defined as
1/16 of the max memory that the balloon device will consume. When the
crosvm main process detects that the system is low on memory, it
immediately increases the balloon size by the increment (unless it has
already reached the max). It then starts 2 timers: one to check for
low memory conditions again in 1 seconds (+ jitter) and another to
check if the system is no longer low on memory in 1 minute (+ jitter)
with a subsequent interval of 30 seconds (+ jitter).
Under persistent low memory conditions the balloon device will consume
the maximum memory after 16 seconds. Once there is enough available
memory the balloon size will shrink back down to 0 after at most 9
minutes.
BUG=chromium:866193
TEST=manual
Start 2 VMs and write out a large file (size > system RAM) in each.
Observe /sys/kernel/mm/chromeos-low_mem/available and see that the
available memory steadily decreases until it goes under the low memory
margin at which point the available memory bounces back up as crosvm
frees up pages.
CQ-DEPEND=CL:1152214
Change-Id: I2046729683aa081c9d7ed039d902ad11737c1d52
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1149155
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Descriptor chains of three descriptors were not having the last
descriptor parsed correctly which resulted in some commands not
properly being responded to.
BUG=None
TEST=build with --features=gpu; null_platform_test
Change-Id: Ia77c7ca485ded7cdcb71fd62e8f6be5c226df1bf
Reviewed-on: https://chromium-review.googlesource.com/1073956
Commit-Ready: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
The original methods for reading and writing to GPU buffers naively
assumed that the mappings returned by GBM were to the first byte in the
buffer. In fact, the returned mapping is to the first pixel of the
mapped rectangle. This would lead to segaults when the copy routine
would breeze past the end of the mapping into segault territory.
This change fixes the read and write algorithms and adds lots more guard
rails in to prevent future undefined behavior (hopefully).
TEST=boot kernel with VT and VIRTIO_GPU
BUG=None
Change-Id: Ia7c968b6dd274551b6d218e2f0b255af6e55bd35
Reviewed-on: https://chromium-review.googlesource.com/1102110
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Basic 2D and 3D support is there. The drm_cursor_test and
null_platform_test in drm-tests should run to completion.
The extra device is hidden behind both a build time feature called 'gpu'
and the device is only added to a VM if the '--gpu' flag is given.
TEST=build with --features=gpu;
drm_cursor_test && null_platform_test
BUG=chromium:837073
Change-Id: Ic91acaaebbee395599d7e1ba41c24c9ed2d84169
Reviewed-on: https://chromium-review.googlesource.com/1036862
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
`PciRoot` represents the root PCI bridge for the system and manages PCI
devices attached to it. The root bridge has its own set of configuration
registers.
Change-Id: I2b15630cf5a0fc5938e66986a65782c6939fcf55
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1072577
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
PCI adds a configuration space to the existing memory mapped IO
supported by BusDevices.
Add the ability to set configuration space as optional to the BusDevice
trait so that ProxyDevice can be shared.
PCI devices can have more than one memory mapped region. Expand the bus
so that it has the ability to pass an absolute address instead of an
offset. This will allow the PCI device to know which BAR is being
written to.
Change-Id: I055cd516c49a74316a9547df471290f05d865b0a
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1103663
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
ARM cares about the status so we need to parse the request correctly and
fill in the status.
Change-Id: I1ffabf556424184017eb64d3b9c68c72b75d0a26
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1139584
Reviewed-by: Stephen Barber <smbarber@chromium.org>
The "supports flush" bit wasn't set in the device features, so the guest
wasn't syncing. Handle the request, which is 0 length so needs special
casing in the `parse` function.
Change-Id: I079611df912cd077362b2ee9925cf730ba86d9e5
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1135940
PciConfiguration manages the PCI configuration space registers for a PCI
device or bridge. Add accessors and setters for the registers that need
to be modified for basic PCI device enumeration.
Change-Id: I4a5a71d55a3c5f7fb52ce81acef51cb4291130c8
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1072574
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Start PCI work by defining an enum to represent the four PCI interrupt
lines.
Change-Id: Ib95a4e4a03f0d6917ed2bed4b1afb97d18ff4f9e
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1072573
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Combine GPU buffer allocation with the system resource allocator making
life easier as only one allocator needs to get passed to the execute
function.
Change-Id: I199eb0fd6b99b629aaec1ae3295e8a1942da5309
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1099856
This function will be used elsewhere in gpu_display.
TEST=None
BUG=None
Change-Id: I58b820511ea5a55a53ad640fdfe7c96d2dbdc73b
Reviewed-on: https://chromium-review.googlesource.com/1105481
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
This provides proper synchronization for guest access to
DMABufs.
Virtio wayland device is given access to the DMA_BUF_SYNC ioctl
in order to implement this. Being able to use this directly in
the virtio wayland device process is important as these calls
can sometimes be relatively expensive and they are frequent
enough that avoiding another context switch is useful for good
performance.
TEST=cache-line artifacts no longer noticeable
BUG=chromium:837209
Change-Id: Ibb8d7c01f70ed5b74afd69288015a65186fec52a
Reviewed-on: https://chromium-review.googlesource.com/1076928
Commit-Ready: David Reveman <reveman@chromium.org>
Tested-by: David Reveman <reveman@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Add a way to iterate over all the descriptors in a descriptor chain.
This is different from AvailIter, which iterates over all the descriptor
chain heads in a queue.
The new iterator struct provides readable() and writable() methods for
iterating over just the readable or writable descriptors, respectively.
BUG=chromium:703939
TEST=none
Change-Id: Iea3fa5bb7662146a2d156a49ce8bb8ef00c522da
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1065172
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Add an is_read_only method to the DescriptorChain struct. This is
easier to read at a glance than `!is_write_only()`, which looks almost
the same as `is_write_only()`.
BUG=chromium:703939
TEST=none
Change-Id: I0cb3b17c30e38804a21d3e63e975157c96879cb4
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1067703
Reviewed-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
