dmaengine: idxd: remove MSIX masking for interrupt handlers

mainline inclusion
from mainline-v5.13
commit a1610461
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I596WO


CVE: NA

Intel-SIG: commit a1610461 dmaengine: idxd: remove MSIX masking for interrupt handlers.
Incremental backporting patches for DSA/IAA on Intel Xeon platform.

--------------------------------

Remove interrupt masking and just let the hard irq handler keep
firing for new events. This is less of a performance impact vs
the MMIO readback inside the pci_msi_{mask,unmas}_irq(). Especially
with a loaded system those flushes can be stuck behind large amounts
of MMIO writes to flush. When guest kernel is running on top of VFIO
mdev, mask/unmask causes a vmexit each time and is not desirable.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/161894523436.3210025.1834640110556139277.stgit@djiang5-desk3.ch.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>