From: Aaron Taylor <ataylor@subgeniuskitty.com>
Date: Wed, 5 May 2021 23:11:24 +0000 (-0700)
Subject: Updated micscif/micscif_rma.c to address changes in callback functions stored in... 
X-Git-Tag: first-build~3
X-Git-Url: https://git.subgeniuskitty.com/xeon-phi-kernel-module/.git/commitdiff_plain/db10dc009b1dea6ccb377d4ecd2d0ecbb5548865

Updated micscif/micscif_rma.c to address changes in callback functions stored in the mmu_notifier_ops struct for use with secondary/client MMUs.
---

diff --git a/micscif/micscif_rma.c b/micscif/micscif_rma.c
index 870746c..32f8adb 100644
--- a/micscif/micscif_rma.c
+++ b/micscif/micscif_rma.c
@@ -57,12 +57,10 @@ void micscif_rma_destroy_tcw(struct rma_mmu_notifier *mmn,
 #ifdef CONFIG_MMU_NOTIFIER
 static void scif_mmu_notifier_release(struct mmu_notifier *mn,
 			struct mm_struct *mm);
-static void scif_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
-				struct mm_struct *mm,
-				unsigned long address);
-static void scif_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
+static int scif_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
 				       struct mm_struct *mm,
-				       unsigned long start, unsigned long end);
+				       unsigned long start, unsigned long end,
+				       bool blockable);
 static void scif_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
 				     struct mm_struct *mm,
 				     unsigned long start, unsigned long end);
@@ -70,7 +68,6 @@ static const struct mmu_notifier_ops scif_mmu_notifier_ops = {
 	.release = scif_mmu_notifier_release,
 	.clear_flush_young = NULL,
 	.change_pte = NULL,/*TODO*/
-	.invalidate_page = scif_mmu_notifier_invalidate_page,
 	.invalidate_range_start = scif_mmu_notifier_invalidate_range_start,
 	.invalidate_range_end = scif_mmu_notifier_invalidate_range_end};
 
@@ -86,30 +83,40 @@ static void scif_mmu_notifier_release(struct mmu_notifier *mn,
 	return;
 }
 
-static void scif_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
-				struct mm_struct *mm,
-				unsigned long address)
-{
-	struct endpt *ep;
-	struct rma_mmu_notifier	*mmn;
-	mmn = container_of(mn, struct rma_mmu_notifier, ep_mmu_notifier);
-	ep = mmn->ep;
-	micscif_rma_destroy_tcw(mmn, ep, true, address, PAGE_SIZE);
-	pr_debug("%s address 0x%lx\n", __func__, address);
-	return;
-}
-
-static void scif_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
+static int scif_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
 				       struct mm_struct *mm,
-				       unsigned long start, unsigned long end)
+				       unsigned long start, unsigned long end,
+				       bool blockable)
 {
 	struct endpt *ep;
 	struct rma_mmu_notifier	*mmn;
 	mmn = container_of(mn, struct rma_mmu_notifier, ep_mmu_notifier);
 	ep = mmn->ep;
+	/*
+	 * The kernel file `include/linux/mmu_notifier.h` states the following
+	 * regarding the invalidate_range_start() callback:
+	 *
+	 *     If blockable argument is set to false then the callback cannot
+	 *     sleep and has to return with -EAGAIN. 0 should be returned
+	 *     otherwise.
+	 *
+	 * The following function executes spin_lock_irqsave(), which feels like it
+	 * qualifies as 'sleep'. However, returning -EAGAIN would require me to
+	 * understand the location and function of all code that calls this
+	 * callback. I do not yet have that understanding.
+	 *
+	 * For now, maintain the original behavior of calling
+	 * micscif_rma_destroy_tcw() every time, accepting the spinlock. If this
+	 * becomes problematic, either figure out all the code that can call this
+	 * function and teach it to understand -EAGAIN, or investigate the `#ifdef
+	 * CONFIG_MMU_NOTIFIER`.
+	 *
+	 * If you ended up here while tracking down a bug and pulling your hair
+	 * out, sorry. :-(
+	 */
 	micscif_rma_destroy_tcw(mmn, ep, true, (uint64_t)start, (uint64_t)(end - start));
 	pr_debug("%s start=%lx, end=%lx\n", __func__, start, end);
-	return;
+	return 0;
 }
 
 static void scif_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,