Am 30.05.22 um 18:00 schrieb Peter Xu:
On Mon, May 30, 2022 at 11:52:54AM -0400, Peter Xu wrote:
On Mon, May 30, 2022 at 11:35:10AM +0200, Christian Borntraeger wrote:
Am 29.05.22 um 22:33 schrieb Heiko Carstens:
[...]
Guess the patch below on top of your patch is what we want.
Just for clarification: if gmap is not NULL then the process is a kvm
process. So, depending on the workload, this optimization makes sense.
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 4608cc962ecf..e1d40ca341b7 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -436,12 +436,11 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED) {
- /*
- * Gmap will need the mmap lock again, so retake it. TODO:
- * only conditionally take the lock when CONFIG_PGSTE set.
- */
- mmap_read_lock(mm);
- goto out_gmap;
+ if (gmap) {
+ mmap_read_lock(mm);
+ goto out_gmap;
+ }
+ goto out;
Hmm, right after I replied I found "goto out" could be problematic, since
all s390 callers of do_exception() will assume it an error condition (side
note: "goto out_gmap" contains one step to clear "fault" to 0). I'll
replace this with "return 0" instead if it looks good to both of you.
I'll wait for a confirmation before reposting. Thanks,
Yes, that sounds good and thank you for double checking.
