Vhost software

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Backends that negotiated this feature should handle both endiannesses and expect this message once per VQ during device configuration ie. Create a session for crypto operation. The server side must return the session id, 0 or positive for success, negative for failure. Note that at this stage the migration is still in precopy mode. Master advises slave that a transition to postcopy mode has happened.

The slave must ensure that shared memory is registered with userfaultfd to cause faulting of non-present pages. Master advises that postcopy migration has now completed. The slave must disable the userfaultfd. The response is an acknowledgement only.

QEMU should retrieve a new one when vm reset. Sets the GPU protocol socket file descriptor, which is passed as ancillary data. The GPU protocol is used to inform the master of rendering state and updates. See vhost-user-gpu. Ask the vhost user backend to disable all rings and reset all internal device state to the initial state, ready to be reinitialized. The backend retains ownership of the device throughout the reset operation.

The slave should return the message with a u64 payload containing the maximum number of memory slots for QEMU to expose to the guest. The value returned by the backend will be capped at the maximum number of ram slots which can be supported by the target platform. The message payload contains a memory region descriptor struct, describing a region of guest memory which the slave device must map in. The message payload contains a memory region descriptor struct, describing a region of guest memory which the slave device must unmap.

Sets host notifier for a specified queue. The queue index is contained in the u64 field of the vring area description. QEMU can mmap the file descriptor based on the size and offset to get a memory range. Slave sends this request to tell QEMU to de-register the existing notifier if any and register the new notifier if the request is sent with a file descriptor. The original vhost-user specification only demands replies for certain commands. This differs from the vhost protocol implementation where commands are sent over an ioctl call and block until the client has completed.

The payload should be set to zero on success or non-zero on failure, unless the message already has an explicit reply body. The response payload gives QEMU a deterministic indication of the result of the command.

Today, QEMU is expected to terminate the main vhost-user loop upon receiving such errors. In future, qemu could be taught to be more resilient for selective requests. See the Communication section for details.

However, it is a good idea to follow the conventions listed here when possible. Users, QEMU or libvirt, can then rely on some common behaviour to avoid heterogeneous configuration and management of the backend programs and facilitate interoperability.

Each backend installed on a host system should come with at least one JSON file that conforms to the vhost-user. Each file informs the management applications about the backend type, and binary location. In addition, it defines rules for management apps for picking the highest priority backend when multiple match the search criteria see VhostUserBackend documentation in the schema file.

If the backend is not capable of enabling a requested feature on the host such as 3D acceleration with virgl , or the initialization failed, the backend should fail to start early and exit with a status! It may also print a message to stderr for further details. The backend program must not daemonize itself, but it may be daemonized by the management layer.

It may also have a restricted access to the system. The following command line options have an expected behaviour. They are mandatory, unless explicitly said differently:. The JSON output is described in the vhost-user. QEMU latest. Client must only pass data between the ring and the backend, when the ring is enabled. If ring is started but disabled, client must process the ring without talking to the backend. User addresses map to the vhost memory region containing that user address.

Get instant access to custom vulnerability scanners and automation features that simplify the pentesting process and produce valuable results. The platform helps you cover all the stages of an engagement, from information gathering to website scanning, network scanning, exploitation and reporting.

A single web server can be configured to run multiple websites at once, under different domain names. These are called virtual hosts or vhosts and they are usually found in shared hosting environments. Example: www. As a penetration tester, finding all the vhosts that run on a web server based on its IP address is important because each website may contain vulnerabilities that affect the same server.

Furthermore, if one website is compromised, there is a high chance that the attacker gains unauthorized access to the other websites also that are running on the same server. Hence, testing all the vhosts is necessary for complete coverage of the penetration test. Sample Report. Use Cases.

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