ffs64() returns INVALID_BIT_INDEX (0xffffU) when it tries to deal with
zero input value. This may happen In calculate_logical_dest_mask() when
the guest tries to write some illegal destination IDs to MSI config
registers of a pt-device. The ffs64() return value is used as per_cpu
array index, and it would cause a page fault.
This patch adds protection to the per_cpu array, making this function
return zero on illegal value. As in logical destination's definition, a
zero logical designation would point to no CPU.
Fixes: 1334349f8
Tracked-On: #8454
Signed-off-by: Wu Zhou <wu.zhou@intel.com>
Reviewed-by: Junjie Mao <junjie.mao@intel.com>
a9860fad05