linux-kernel - [PATCH v10 30/38] x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit

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Date:   Wed, 13 Sep 2023 21:47:57 -0700
From:   Xin Li <xin3.li@...el.com>
To:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-edac@...r.kernel.org, linux-hyperv@...r.kernel.org,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        peterz@...radead.org, jgross@...e.com, ravi.v.shankar@...el.com,
        mhiramat@...nel.org, andrew.cooper3@...rix.com,
        jiangshanlai@...il.com
Subject: [PATCH v10 30/38] x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled,
otherwise the existing IDT code is chosen.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Tested-by: Shan Kang <shan.kang@...el.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
---
 arch/x86/entry/entry_64.S      | 6 ++++++
 arch/x86/entry/entry_64_fred.S | 1 +
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9cdb61ea91de..c9e14617dd3f 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -309,7 +309,13 @@ SYM_CODE_START(ret_from_fork_asm)
 	 * and unwind should work normally.
 	 */
 	UNWIND_HINT_REGS
+
+#ifdef CONFIG_X86_FRED
+	ALTERNATIVE "jmp swapgs_restore_regs_and_return_to_usermode", \
+		    "jmp asm_fred_exit_user", X86_FEATURE_FRED
+#else
 	jmp	swapgs_restore_regs_and_return_to_usermode
+#endif
 SYM_CODE_END(ret_from_fork_asm)
 .popsection
 
diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S
index 37a1dd5e8ace..5781c3411b44 100644
--- a/arch/x86/entry/entry_64_fred.S
+++ b/arch/x86/entry/entry_64_fred.S
@@ -32,6 +32,7 @@
 SYM_CODE_START_NOALIGN(asm_fred_entrypoint_user)
 	FRED_ENTER
 	call	fred_entry_from_user
+SYM_INNER_LABEL(asm_fred_exit_user, SYM_L_GLOBAL)
 	FRED_EXIT
 	ERETU
 SYM_CODE_END(asm_fred_entrypoint_user)
-- 
2.34.1