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From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	hpa@zytor.com, Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Mike Rapoport <rppt@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Brijesh Singh <brijesh.singh@amd.com>,
	linux-kernel@vger.kernel.org, Joerg Roedel <jroedel@suse.de>,
	Joerg Roedel <joro@8bytes.org>
Subject: [PATCH v4 1/4] x86/realmode: Add comment for Global bit usage in trampline_pgd
Date: Thu,  2 Dec 2021 16:32:23 +0100	[thread overview]
Message-ID: <20211202153226.22946-2-joro@8bytes.org> (raw)
In-Reply-To: <20211202153226.22946-1-joro@8bytes.org>

From: Joerg Roedel <jroedel@suse.de>

Document the fact that using the trampoline_pgd will result in the
creation of global TLB entries in the user range of the address
space.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/mm/init.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1895986842b9..4ba024d5b63a 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -714,6 +714,11 @@ static void __init memory_map_bottom_up(unsigned long map_start,
 static void __init init_trampoline(void)
 {
 #ifdef CONFIG_X86_64
+	/*
+	 * The code below will alias kernel page-tables in the user-range of the
+	 * address space, including the Global bit. So global TLB entries will
+	 * be created when using the trampoline page-table.
+	 */
 	if (!kaslr_memory_enabled())
 		trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)];
 	else
-- 
2.34.0


  reply	other threads:[~2021-12-02 15:34 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-02 15:32 [PATCH v4 0/4] x86/mm: Fix some issues with using trampoline_pgd Joerg Roedel
2021-12-02 15:32 ` Joerg Roedel [this message]
2021-12-06 21:57   ` [tip: x86/mm] x86/realmode: Add comment for Global bit usage in trampoline_pgd tip-bot2 for Joerg Roedel
2021-12-02 15:32 ` [PATCH v4 2/4] x86/mm/64: Flush global TLB on boot and AP bringup Joerg Roedel
2021-12-06 21:57   ` [tip: x86/mm] " tip-bot2 for Joerg Roedel
2021-12-02 15:32 ` [PATCH v4 3/4] x86/mm: Flush global TLB when switching to trampoline page-table Joerg Roedel
2021-12-06 21:57   ` [tip: x86/mm] " tip-bot2 for Joerg Roedel
2021-12-02 15:32 ` [PATCH v4 4/4] x86/64/mm: Map all kernel memory into trampoline_pgd Joerg Roedel
2021-12-03 10:04   ` [tip: x86/urgent] " tip-bot2 for Joerg Roedel

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