linux-kernel - [RFC PATCH PoC 03/11] x86/boot: Disregard __supported_pte_mask in __startup

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Message-ID: <20250423110948.1103030-16-ardb+git@google.com>
Date: Wed, 23 Apr 2025 13:09:52 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org, mingo@...nel.org, Ard Biesheuvel <ardb@...nel.org>
Subject: [RFC PATCH PoC 03/11] x86/boot: Disregard __supported_pte_mask in __startup_64()

From: Ard Biesheuvel <ardb@...nel.org>

__supported_pte_mask is statically initialized to U64_MAX and never
assigned until long after the startup code executes that creates the
initial page tables. So applying the mask is unnecessary, and can be
avoided.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/boot/startup/map_kernel.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/boot/startup/map_kernel.c b/arch/x86/boot/startup/map_kernel.c
index 0eac3f17dbd3..099ae2559336 100644
--- a/arch/x86/boot/startup/map_kernel.c
+++ b/arch/x86/boot/startup/map_kernel.c
@@ -179,8 +179,6 @@ unsigned long __head __startup_64(unsigned long p2v_offset,
 	pud[(i + 1) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags;
 
 	pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL;
-	/* Filter out unsupported __PAGE_KERNEL_* bits: */
-	pmd_entry &= __supported_pte_mask;
 	pmd_entry += sme_get_me_mask();
 	pmd_entry +=  physaddr;
 
-- 
2.49.0.805.g082f7c87e0-goog