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From:   Lai Jiangshan <jiangshanlai@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     x86@kernel.org, Lai Jiangshan <laijs@linux.alibaba.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH V3 15/49] x86/entry: Add C verion of SWITCH_TO_KERNEL_CR3 as switch_to_kernel_cr3()
Date:   Thu, 14 Oct 2021 11:33:38 +0800
Message-Id: <20211014033414.16321-10-jiangshanlai@gmail.com>
In-Reply-To: <20211014031413.14471-1-jiangshanlai@gmail.com>
References: <20211014031413.14471-1-jiangshanlai@gmail.com>
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From: Lai Jiangshan <laijs@linux.alibaba.com>

The C version switch_to_kernel_cr3() implements SWITCH_TO_KERNEL_CR3().

No functional difference intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
 arch/x86/entry/entry64.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c
index 9813a30dbadb..9a5c535b1ddf 100644
--- a/arch/x86/entry/entry64.c
+++ b/arch/x86/entry/entry64.c
@@ -14,3 +14,27 @@
 #include <asm/traps.h>
 
 extern unsigned char asm_load_gs_index_gs_change[];
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+static __always_inline void pti_switch_to_kernel_cr3(unsigned long user_cr3)
+{
+	/*
+	 * Clear PCID and "PAGE_TABLE_ISOLATION bit", point CR3
+	 * at kernel pagetables:
+	 */
+	unsigned long cr3 = user_cr3 & ~PTI_USER_PGTABLE_AND_PCID_MASK;
+
+	if (static_cpu_has(X86_FEATURE_PCID))
+		cr3 |= X86_CR3_PCID_NOFLUSH;
+
+	native_write_cr3(cr3);
+}
+
+static __always_inline void switch_to_kernel_cr3(void)
+{
+	if (static_cpu_has(X86_FEATURE_PTI))
+		pti_switch_to_kernel_cr3(__native_read_cr3());
+}
+#else
+static __always_inline void switch_to_kernel_cr3(void) {}
+#endif
-- 
2.19.1.6.gb485710b