powerpc/64s/radix: introduce options to disable use of the tlbie instruction

Introduce two options to control the use of the tlbie instruction. A
boot time option which completely disables the kernel using the
instruction, this is currently incompatible with HASH MMU, KVM, and
coherent accelerators.

And a debugfs option can be switched at runtime and avoids using tlbie
for invalidating CPU TLBs for normal process and kernel address
mappings. Coherent accelerators are still managed with tlbie, as will
KVM partition scope translations.

Cross-CPU TLB flushing is implemented with IPIs and tlbiel. This is a
basic implementation which does not attempt to make any optimisation
beyond the tlbie implementation.

This is useful for performance testing among other things. For example
in certain situations on large systems, using IPIs may be faster than
tlbie as they can be directed rather than broadcast. Later we may also
take advantage of the IPIs to do more interesting things such as trim
the mm cpumask more aggressively.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190902152931.17840-7-npiggin@gmail.com

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/misc/cxl/main.c b/drivers/misc/cxl/main.c
index 482a2c1b340a..43b312d06e3e 100644
--- a/drivers/misc/cxl/main.c
+++ b/drivers/misc/cxl/main.c
@@ -18,6 +18,7 @@
 #include <linux/sched/task.h>
 
 #include <asm/cputable.h>
+#include <asm/mmu.h>
 #include <misc/cxl-base.h>
 
 #include "cxl.h"
@@ -315,6 +316,9 @@ static int __init init_cxl(void)
 {
 	int rc = 0;
 
+	if (!tlbie_capable)
+		return -EINVAL;
+
 	if ((rc = cxl_file_init()))
 		return rc;