diff --git a/scripts/ci/cmake/ci-el8-icc-ompi.cmake b/scripts/ci/cmake/ci-el8-icc-ompi.cmake
index c191d79c26..6f8803e44d 100644
--- a/scripts/ci/cmake/ci-el8-icc-ompi.cmake
+++ b/scripts/ci/cmake/ci-el8-icc-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  icc)
 set(ENV{CXX} icpc)
 set(ENV{FC}  ifort)
@@ -28,9 +24,6 @@ CMAKE_C_FLAGS:STRING=-Wall -diag-disable=10441
 CMAKE_C_FLAGS_DEBUG:STRING=-g -O0
 CMAKE_CXX_FLAGS:STRING=-Wall -diag-disable=10441
 CMAKE_CXX_FLAGS_DEBUG:STRING=-g -O0
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Unix Makefiles")
diff --git a/scripts/ci/cmake/ci-el8-oneapi-ompi.cmake b/scripts/ci/cmake/ci-el8-oneapi-ompi.cmake
index 7a637d1888..8a1c5e5fa9 100644
--- a/scripts/ci/cmake/ci-el8-oneapi-ompi.cmake
+++ b/scripts/ci/cmake/ci-el8-oneapi-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  icx)
 set(ENV{CXX} icpx)
 set(ENV{FC}  ifort) # oneapi fortran compiler currently has issues
@@ -29,9 +25,6 @@ CMAKE_C_FLAGS_DEBUG:STRING=-g -O0
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS_DEBUG:STRING=-g -O0
 CMAKE_Fortran_FLAGS:STRING=-W1
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Unix Makefiles")
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-clang10-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-clang10-ompi.cmake
index e62ed9b57a..447c304316 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-clang10-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-clang10-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  clang-10)
 set(ENV{CXX} clang++-10)
 set(ENV{FC}  gfortran-11)
@@ -35,9 +31,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Ninja")
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-clang6-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-clang6-ompi.cmake
index 2bdf2c410d..bfe89a699c 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-clang6-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-clang6-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  clang-6.0)
 set(ENV{CXX} clang++-6.0)
 set(ENV{FC}  gfortran-11)
@@ -36,9 +32,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 # We have a dedicated build for this setup without MPI
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-clang6-static-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-clang6-static-ompi.cmake
index 4b338b9c89..71c0f9710e 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-clang6-static-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-clang6-static-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  clang-6.0)
 set(ENV{CXX} clang++-6.0)
 set(ENV{FC}  gfortran-11)
@@ -37,9 +33,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Ninja")
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-gcc10-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-gcc10-ompi.cmake
index 0f80809145..6463d8f72a 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-gcc10-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-gcc10-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  gcc)
 set(ENV{CXX} g++)
 set(ENV{FC}  gfortran)
@@ -35,9 +31,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 # We have a dedicated build for this setup without MPI
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-gcc11-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-gcc11-ompi.cmake
index 70cd4b3552..a686bb0c87 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-gcc11-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-gcc11-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  gcc)
 set(ENV{CXX} g++)
 set(ENV{FC}  gfortran)
@@ -35,9 +31,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Ninja")
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-gcc8-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-gcc8-ompi.cmake
index 70cd4b3552..a686bb0c87 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-gcc8-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-gcc8-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  gcc)
 set(ENV{CXX} g++)
 set(ENV{FC}  gfortran)
@@ -35,9 +31,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Ninja")
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-gcc8-static-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-gcc8-static-ompi.cmake
index 9f4b991bc8..88ed69ff7a 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-gcc8-static-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-gcc8-static-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  gcc)
 set(ENV{CXX} g++)
 set(ENV{FC}  gfortran)
@@ -37,9 +33,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Ninja")
diff --git a/scripts/ci/cmake/ci-ubuntu20.04-gcc9-ompi.cmake b/scripts/ci/cmake/ci-ubuntu20.04-gcc9-ompi.cmake
index 70cd4b3552..a686bb0c87 100644
--- a/scripts/ci/cmake/ci-ubuntu20.04-gcc9-ompi.cmake
+++ b/scripts/ci/cmake/ci-ubuntu20.04-gcc9-ompi.cmake
@@ -1,7 +1,3 @@
-include(ProcessorCount)
-ProcessorCount(NCPUS)
-math(EXPR N2CPUS "${NCPUS}*2")
-
 set(ENV{CC}  gcc)
 set(ENV{CXX} g++)
 set(ENV{FC}  gfortran)
@@ -35,9 +31,6 @@ CMAKE_CXX_COMPILER_LAUNCHER=ccache
 CMAKE_C_FLAGS:STRING=-Wall
 CMAKE_CXX_FLAGS:STRING=-Wall
 CMAKE_Fortran_FLAGS:STRING=-Wall
-
-MPIEXEC_EXTRA_FLAGS:STRING=--allow-run-as-root --oversubscribe
-MPIEXEC_MAX_NUMPROCS:STRING=${N2CPUS}
 ")
 
 set(CTEST_CMAKE_GENERATOR "Ninja")
diff --git a/scripts/ci/gh-actions/run.sh b/scripts/ci/gh-actions/run.sh
index 86d12a4b49..5dcfcca7aa 100755
--- a/scripts/ci/gh-actions/run.sh
+++ b/scripts/ci/gh-actions/run.sh
@@ -72,13 +72,20 @@ mkdir -p "${TMPDIR}"
 # OpenMPI specific setup and workarounds
 if [[ "${GH_YML_MATRIX_PARALLEL}" =~ ompi && "${GH_YML_BASE_OS}" != "Windows" ]]
 then
-  # Quiet some warnings from OpenMPI
-  export OMPI_MCA_btl_base_warn_component_unused=0
-  export OMPI_MCA_btl_vader_single_copy_mechanism=none
+  # Enable run as root
+  export OMPI_ALLOW_RUN_AS_ROOT=1
+  export OMPI_ALLOW_RUN_AS_ROOT_CONFIRM=1
 
   # Enable overscription in OpenMPI
-  export OMPI_MCA_rmaps_base_oversubscribe=1
+  export OMPI_MCA_rmaps_base_oversubscribe=true
   export OMPI_MCA_hwloc_base_binding_policy=none
+
+  # Only use loop interface
+  export OMPI_MCA_btl_tcp_if_include=lo
+
+  # Quiet some warnings from OpenMPI
+  export OMPI_MCA_btl_base_warn_component_unused=0
+  export OMPI_MCA_btl_vader_single_copy_mechanism=none
 fi
 
 if [[ "${GH_YML_MATRIX_PARALLEL}" =~ ompi ]]
@@ -89,6 +96,9 @@ fi
 # Make sure staging tests use localhost
 export ADIOS2_IP=127.0.0.1
 
+# We already paralelize with mpi (MGARD uses OMP)
+export OMP_NUM_THREADS=1
+
 # Load any additional setup scripts
 if [ -f gha/scripts/ci/setup-run/ci-${GH_YML_JOBNAME}.sh ]
 then