docs/devel/multi-process.rst

18 infrastructure, a guest that compromised its hypervisor could
23 monolithic program that provides many features to the VMs it services.
27 limit each component in the system to only access the resources that
69 interface points where the QEMU functions that perform device emulation
70 can be separated from the QEMU functions that manage the emulation of
94 a couple of existing QEMU features that can run emulation code
105 application is a daemon process that can be contacted via a known UNIX
124 executes instructions that cannot be executed by virtual HW mode,
128 One of the events that can cause a return to QEMU is when a guest device
133 virtio code by setting up an eventfd file descriptor that the vhost
144 that triggers the device interrupt in the guest when the eventfd is
176 basic is that vhost uses custom virtio device drivers which always
184 Another difference is that in the vhost user model, a single daemon can
191 object code (e.g., the code that implements disk images for disk driver
213 backends that QEMU has.
231 (e.g., disk, network, etc.) in a single process, so that all backends of
238 socket that connects with the Proxy object. This is a required argument.
262 sub-option to this option specifies the Unix socket that connects
300 "object" super-class. The sub-classes that are of interest here are the
312 It is worth noting that the same proxy object is used to mediate with
339 MMIO handlers, or creating a child bus that other proxy devices can be
352 functions that QEMU will invoke when the guest accesses the device's
365 PCI devices also have a configuration space that can be accessed by the
375 "pci-device-proxy" class that can serve as the parent of a PCI device
378 methods with ones that forward these operations to the emulation
384 A proxy for a device that generates interrupts will need to create a
395 remote device's *vmstate*; that will be handled by the remote process
410 that the emulation process can ``mmap()`` to directly access guest
413 *-object memory-backend-file,share=on* and setting that memory backend
426 to the memory region that will forward unmaps to the emulation process
456 The parts of QEMU that the emulation program will need include the
506 accomplish that, guest BAR programming must also be forwarded from QEMU
535 install an address space handler at that address which forwards the MSI
552 that physical address can be translated to a local virtual address. The
559 invoked, the IOTLB cache will be searched for an entry that will map the
576 *QEMUfile* that can be passed to ``qemu_save_device_state()`` to send
584 The messages that are required to be sent between QEMU and the emulation
594 that it does not pass any data with the event indication, so it cannot
595 handle guest loads or guest stores that carry store data. This concept
600 descriptor that QEMU can use for configuration, and a slave descriptor
601 that the emulation process can use to receive MMIO notifications. QEMU
610 The guest physical range structure describes the address range that a
635 physical range the MMIO was within, the offset within that range, the
637 includes a sequence number that can be used to reply to the MMIO, and
638 the CPU that issued the MMIO.
659 are two queues: pending queue is for MMIOs that haven't been read by the
660 emulation program, and the sent queue is for MMIOs that haven't been
672 that haven't been replied to, in order to satisfy the PCI constraint
673 that a load to a device will not complete until all previous stores to
674 that device have been completed.
720 *KVM\_DEV\_USER\_SLAVE\_FD* creates the slave file descriptor that will
726 address range that the slave descriptor will receive MMIO notifications
728 argument. For buses that assign addresses to devices dynamically, this
738 *KVM\_DEV\_USER\_TIMEOUT* will configure a timeout value that specifies
775 There are several ioctl()s that can be performed on the slave
787 the size of load operations that are allowed.
817 process reply before re-starting the guest. Loads that do not have
820 ordering demands that a load cannot complete before all older stores to
835 application does, where the QEMU process sets up *eventfds* that cause
875 data contains a vector that is programmed by the guest, A device may have
911 enforce that the differing processes can only access the objects they
950 and non-network emulation process, and only that type can access the