drm/xe/vm_doc: Fix some typos

 * VM bind (create GPU mapping for a BO or userptr)

 * ================================================

 *

 * Creates GPU mapings for a BO or userptr within a VM. VM binds uses the same

 * Creates GPU mappings for a BO or userptr within a VM. VM binds uses the same

 * in / out fence interface (struct drm_xe_sync) as execs which allows users to

 * think of binds and execs as more or less the same operation.

 *

 * Deferred binds in fault mode

 * ----------------------------

 *

 * In a VM is in fault mode (TODO: link to fault mode), new bind operations that

 * create mappings are by default are deferred to the page fault handler (first

 * If a VM is in fault mode (TODO: link to fault mode), new bind operations that

 * create mappings are by default deferred to the page fault handler (first

 * use). This behavior can be overriden by setting the flag

 * DRM_XE_VM_BIND_FLAG_IMMEDIATE which indicates to creating the mapping

 * immediately.

 *

 * A VM in compute mode enables long running workloads and ultra low latency

 * submission (ULLS). ULLS is implemented via a continuously running batch +

 * semaphores. This enables to the user to insert jump to new batch commands

 * semaphores. This enables the user to insert jump to new batch commands

 * into the continuously running batch. In both cases these batches exceed the

 * time a dma fence is allowed to exist for before signaling, as such dma fences

 * are not used when a VM is in compute mode. User fences (TODO: link user fence

 * Once all preempt fences are signaled for a VM the kernel can safely move the

 * memory and kick the rebind worker which resumes all the engines execution.

 *

 * A preempt fence, for every engine using the VM, is installed the VM's

 * A preempt fence, for every engine using the VM, is installed into the VM's

 * dma-resv DMA_RESV_USAGE_PREEMPT_FENCE slot. The same preempt fence, for every

 * engine using the VM, is also installed into the same dma-resv slot of every

 * external BO mapped in the VM.

 * signaling, and memory allocation is usually required to resolve a page

 * fault, but memory allocation is not allowed to gate dma fence signaling. As

 * such, dma fences are not allowed when VM is in fault mode. Because dma-fences

 * are not allowed, long running workloads and ULLS are enabled on a faulting

 * are not allowed, only long running workloads and ULLS are enabled on a faulting

 * VM.

 *

 * Defered VM binds

 * Notice no rebind is issued in the access counter handler as the rebind will

 * be issued on next page fault.

 *

 * Cavets with eviction / user pointer invalidation

 * ------------------------------------------------

 * Caveats with eviction / user pointer invalidation

 * -------------------------------------------------

 *

 * In the case of eviction and user pointer invalidation on a faulting VM, there

 * is no need to issue a rebind rather we just need to blow away the page tables

 * for the VMAs and the page fault handler will rebind the VMAs when they fault.

 * The cavet is to update / read the page table structure the VM global lock is

 * neeeed. In both the case of eviction and user pointer invalidation locks are

 * The caveat is to update / read the page table structure the VM global lock is

 * needed. In both the case of eviction and user pointer invalidation locks are

 * held which make acquiring the VM global lock impossible. To work around this

 * every VMA maintains a list of leaf page table entries which should be written

 * to zero to blow away the VMA's page tables. After writing zero to these

 * VM global lock (vm->lock) - rw semaphore lock. Outer most lock which protects

 * the list of userptrs mapped in the VM, the list of engines using this VM, and

 * the array of external BOs mapped in the VM. When adding or removing any of the

 * aforemented state from the VM should acquire this lock in write mode. The VM

 * aforementioned state from the VM should acquire this lock in write mode. The VM

 * bind path also acquires this lock in write while the exec / compute mode

 * rebind worker acquire this lock in read mode.

 * rebind worker acquires this lock in read mode.

 *

 * VM dma-resv lock (vm->ttm.base.resv->lock) - WW lock. Protects VM dma-resv

 * slots which is shared with any private BO in the VM. Expected to be acquired