[tip: x86/urgent] x86/mm/pat: don't collapse pages without PSE set

[tip-bot2 for Juergen Gross]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     1dbf30fdb5e57fb2c39f17f35f2b544d5de34397
Gitweb:        https://git.kernel.org/tip/1dbf30fdb5e57fb2c39f17f35f2b544d5de34397
Author:        Juergen Gross <jgross@xxxxxxxx>
AuthorDate:    Tue, 03 Jun 2025 14:14:41 +03:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 11 Jun 2025 11:20:51 +02:00

x86/mm/pat: don't collapse pages without PSE set

Collapsing pages to a leaf PMD or PUD should be done only if
X86_FEATURE_PSE is available, which is not the case when running e.g.
as a Xen PV guest.

Fixes: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20250528123557.12847-3-jgross@xxxxxxxx
---
 arch/x86/mm/pat/set_memory.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 46edc11..8834c76 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1257,6 +1257,9 @@ static int collapse_pmd_page(pmd_t *pmd, unsigned long addr,
 	pgprot_t pgprot;
 	int i = 0;
 
+	if (!cpu_feature_enabled(X86_FEATURE_PSE))
+		return 0;
+
 	addr &= PMD_MASK;
 	pte = pte_offset_kernel(pmd, addr);
 	first = *pte;