drm/xe: Add mnemonic error reason to page fault diagnostics

xe_pagefault_print() was firing without indicating why servicing of a
fault failed, making it hard to distinguish benign races (e.g. a VM's
file descriptor closing mid-fault) from real bugs.

Add enum xe_pagefault_error, uniquely identifying the high-level point
at which xe_pagefault_service(), xe_pagefault_handle_vma(), and
xe_svm_handle_pagefault() fail. Since consumer.page_addr is always
page (4K) aligned, steal the reserved low byte to carry this code
without growing struct xe_pagefault. Add xe_pagefault_set_error() /
xe_pagefault_get_error() to encode/decode it, and xe_pagefault_addr()
as the single accessor for the real (masked) faulted address; update
all real address consumers (xe_pagefault_match(), cache alignment,
xe_vm_add_fault_entry_pf()) to go through it instead of reading
consumer.page_addr directly. xe_pagefault_set_start_addr() now
preserves any already-recorded error bits rather than clobbering them.

xe_pagefault_print() decodes the error via a new
xe_pagefault_error_to_str() and reports it in an added "Error:" line.

xe_pagefault_asid_to_vm() now distinguishes an ASID with no VM at all
(XE_PAGEFAULT_ERROR_VM_NOT_FOUND, e.g. the owning file descriptor was
already closed) from a VM found but not in fault mode
(XE_PAGEFAULT_ERROR_VM_NOT_IN_FAULT_MODE).

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Assisted-by: GitHub_Copilot:claude-sonnet-5
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patch.msgid.link/20260917203850.321385-1-matthew.brost@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

0 files changed, 0 insertions, 0 deletions