x86/apic: Fix atomic update of offset in reserve_eilvt_offset()

The detection of atomic update failure in reserve_eilvt_offset() is
not correct. The value returned by atomic_cmpxchg() should be compared
to the old value from the location to be updated.

If these two are the same, then atomic update succeeded and
"eilvt_offsets[offset]" location is updated to "new" in an atomic way.

Otherwise, the atomic update failed and it should be retried with the
value from "eilvt_offsets[offset]" - exactly what atomic_try_cmpxchg()
does in a correct and more optimal way.

Fixes: a68c439b1966c ("apic, x86: Check if EILVT APIC registers are available (AMD only)")
Signed-off-by: Uros Bizjak <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions