FAILED: patch "[PATCH] Revert "x86/mm/ident_map: Use gbpages only where full GB page" failed to apply to 6.8-stable tree

The patch below does not apply to the 6.8-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.8.y
git checkout FETCH_HEAD
git cherry-pick -x c567f2948f57bdc03ed03403ae0234085f376b7d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024040116-epidermis-early-a05d@gregkh' --subject-prefix 'PATCH 6.8.y' HEAD^..

Possible dependencies:

c567f2948f57 ("Revert "x86/mm/ident_map: Use gbpages only where full GB page should be mapped."") 0a845e0f6348 ("mm/treewide: replace pud_large() with pud_leaf()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c567f2948f57bdc03ed03403ae0234085f376b7d Mon Sep 17 00:00:00 2001
From: Ingo Molnar <[email protected]>
Date: Mon, 25 Mar 2024 11:47:51 +0100
Subject: [PATCH] Revert "x86/mm/ident_map: Use gbpages only where full GB page
should be mapped."

This reverts commit d794734c9bbfe22f86686dc2909c25f5ffe1a572.

While the original change tries to fix a bug, it also unintentionally broke existing systems, see the regressions reported at:

https://lore.kernel.org/all/[email protected]/

Since d794734c9bbf was also marked for -stable, let's back it out before causing more damage.

Note that due to another upstream change the revert was not 100% automatic:

0a845e0f6348 mm/treewide: replace pud_large() with pud_leaf()

index a204a332c71f..968d7005f4a7 100644
@@ -26,31 +26,18 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
 	for (; addr < end; addr = next) {
 		pud_t *pud = pud_page + pud_index(addr);
 		pmd_t *pmd;
-		bool use_gbpage;
 
 		next = (addr & PUD_MASK) + PUD_SIZE;
 		if (next > end)
 			next = end;
 
-		/* if this is already a gbpage, this portion is already mapped */
-		if (pud_leaf(*pud))
-			continue;
-
-		/* Is using a gbpage allowed? */
-		use_gbpage = info->direct_gbpages;
-
-		/* Don't use gbpage if it maps more than the requested region. */
-		/* at the begining: */
-		use_gbpage &= ((addr & ~PUD_MASK) == 0);
-		/* ... or at the end: */
-		use_gbpage &= ((next & ~PUD_MASK) == 0);
-
-		/* Never overwrite existing mappings */
-		use_gbpage &= !pud_present(*pud);
-
-		if (use_gbpage) {
+		if (info->direct_gbpages) {
 			pud_t pudval;
 
+			if (pud_present(*pud))
+				continue;
+
+			addr &= PUD_MASK;
 			pudval = __pud((addr - info->offset) | info->page_flag);
 			set_pud(pud, pudval);
 			continue;

From: Ingo Molnar <[email protected]>

This reverts commit d794734c9bbfe22f86686dc2909c25f5ffe1a572.

While the original change tries to fix a bug, it also unintentionally broke existing systems, see the regressions reported at:

https://lore.kernel.org/all/[email protected]/

Since d794734c9bbf was also marked for -stable, let's back it out before causing more damage.

Note that due to another upstream change the revert was not 100% automatic:

0a845e0f6348 mm/treewide: replace pud_large() with pud_leaf()

---

Thought I'd try and be of help. The pud_large() / pud_leaf() change is what caused the difficulty in reversion.

 arch/x86/mm/ident_map.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

index f50cc210a981..968d7005f4a7 100644
@@ -26,31 +26,18 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
 	for (; addr < end; addr = next) {
 		pud_t *pud = pud_page + pud_index(addr);
 		pmd_t *pmd;
-		bool use_gbpage;
 
 		next = (addr & PUD_MASK) + PUD_SIZE;
 		if (next > end)
 			next = end;
 
-		/* if this is already a gbpage, this portion is already mapped */
-		if (pud_large(*pud))
-			continue;
-
-		/* Is using a gbpage allowed? */
-		use_gbpage = info->direct_gbpages;
-
-		/* Don't use gbpage if it maps more than the requested region. */
-		/* at the begining: */
-		use_gbpage &= ((addr & ~PUD_MASK) == 0);
-		/* ... or at the end: */
-		use_gbpage &= ((next & ~PUD_MASK) == 0);
-
-		/* Never overwrite existing mappings */
-		use_gbpage &= !pud_present(*pud);
-
-		if (use_gbpage) {
+		if (info->direct_gbpages) {
 			pud_t pudval;
 
+			if (pud_present(*pud))
+				continue;
+
+			addr &= PUD_MASK;
 			pudval = __pud((addr - info->offset) | info->page_flag);
 			set_pud(pud, pudval);
 			continue;

2.26.2