linux-kernel - [PATCH 20/21] x86/mm/asi: don't use global pages when ASI enabled

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Message-ID: <20250924-b4-asi-page-alloc-v1-20-2d861768041f@google.com>
Date: Wed, 24 Sep 2025 14:59:55 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: jackmanb@...gle.com, Andy Lutomirski <luto@...nel.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, 
	Johannes Weiner <hannes@...xchg.org>, Zi Yan <ziy@...dia.com>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, Yuanchu Xie <yuanchu@...gle.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>
Cc: peterz@...radead.org, bp@...en8.de, dave.hansen@...ux.intel.com, 
	mingo@...hat.com, tglx@...utronix.de, akpm@...ux-foundation.org, 
	david@...hat.com, derkling@...gle.com, junaids@...gle.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, reijiw@...gle.com, 
	rientjes@...gle.com, rppt@...nel.org, vbabka@...e.cz, x86@...nel.org, 
	yosry.ahmed@...ux.dev
Subject: [PATCH 20/21] x86/mm/asi: don't use global pages when ASI enabled

For the same reason as with PTI, ASI means kernel pages can't be global:
TLB entries from the unrestricted address space must not carry over into
the restricted address space.

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
 arch/x86/mm/init.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 8fd34475af7ccd49d0124e13a87342d3bfef3e05..45bbe764ca4e0abc13d41590dc4ff466180cca31 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -249,8 +249,9 @@ static void __init probe_page_size_mask(void)
 
 	/* By the default is everything supported: */
 	__default_kernel_pte_mask = __supported_pte_mask;
-	/* Except when with PTI where the kernel is mostly non-Global: */
-	if (cpu_feature_enabled(X86_FEATURE_PTI))
+	/* Except when with PTI/ASI where the kernel is mostly non-Global: */
+	if (cpu_feature_enabled(X86_FEATURE_PTI) ||
+	    cpu_feature_enabled(X86_FEATURE_ASI))
 		__default_kernel_pte_mask &= ~_PAGE_GLOBAL;
 
 	/* Enable 1 GB linear kernel mappings if available: */

-- 
2.50.1