linux-kernel - [PATCH v2 3/3] x86/fred: Enable FRED right after init_mem

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Message-ID: <20240709154048.3543361-4-xin@zytor.com>
Date: Tue,  9 Jul 2024 08:40:48 -0700
From: "Xin Li (Intel)" <xin@...or.com>
To: linux-kernel@...r.kernel.org
Cc: hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, peterz@...radead.org,
        andrew.cooper3@...rix.com, nik.borisov@...e.com,
        houwenlong.hwl@...group.com
Subject: [PATCH v2 3/3] x86/fred: Enable FRED right after init_mem_mapping()

Enable FRED right after init_mem_mapping() to avoid #PF handler,
exc_page_fault(), fetching its faulting address from the stack
before FRED is enabled.

Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code")
Reported-by: Hou Wenlong <houwenlong.hwl@...group.com>
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Xin Li (Intel) <xin@...or.com>
---
 arch/x86/kernel/cpu/common.c |  6 +-----
 arch/x86/kernel/setup.c      | 11 ++++++++++-
 arch/x86/kernel/smpboot.c    |  6 ++++++
 arch/x86/kernel/traps.c      |  4 ++++
 4 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 6de12b3c1b04..42d4136ed6ac 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2195,12 +2195,8 @@ void cpu_init_exception_handling(void)
 	/* GHCB needs to be setup to handle #VC. */
 	setup_ghcb();
 
-	if (cpu_feature_enabled(X86_FEATURE_FRED)) {
-		cpu_init_fred_exceptions();
-		cpu_init_fred_rsps();
-	} else {
+	if (!cpu_feature_enabled(X86_FEATURE_FRED))
 		load_current_idt();
-	}
 }
 
 /*
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 728927e4ba51..36403b901eb2 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -39,6 +39,7 @@
 #include <asm/coco.h>
 #include <asm/cpu.h>
 #include <asm/efi.h>
+#include <asm/fred.h>
 #include <asm/gart.h>
 #include <asm/hypervisor.h>
 #include <asm/io_apic.h>
@@ -1040,7 +1041,15 @@ void __init setup_arch(char **cmdline_p)
 
 	init_mem_mapping();
 
-	idt_setup_early_pf();
+	/*
+	 * init_mem_mapping() uses early IDT to setup memory mappings, thus FRED
+	 * can't be enabled earlier than that, unless FRED adds support to setup
+	 * memory mappings.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_FRED))
+		cpu_init_fred_exceptions();
+	else
+		idt_setup_early_pf();
 
 	/*
 	 * Update mmu_cr4_features (and, indirectly, trampoline_cr4_features)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 0c35207320cb..0d83377f9dcd 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -64,6 +64,7 @@
 #include <asm/acpi.h>
 #include <asm/cacheinfo.h>
 #include <asm/desc.h>
+#include <asm/fred.h>
 #include <asm/nmi.h>
 #include <asm/irq.h>
 #include <asm/realmode.h>
@@ -248,6 +249,11 @@ static void notrace start_secondary(void *unused)
 
 	cpu_init_exception_handling();
 
+	if (cpu_feature_enabled(X86_FEATURE_FRED)) {
+		cpu_init_fred_exceptions();
+		cpu_init_fred_rsps();
+	}
+
 	/*
 	 * Load the microcode before reaching the AP alive synchronization
 	 * point below so it is not part of the full per CPU serialized
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 6afb41e6cbbb..81648bd07576 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1407,6 +1407,10 @@ void __init trap_init(void)
 	/* Init cpu_entry_area before IST entries are set up */
 	setup_cpu_entry_areas();
 
+	/* FRED RSPs pointing to memory from CPU entry areas */
+	if (cpu_feature_enabled(X86_FEATURE_FRED))
+		cpu_init_fred_rsps();
+
 	/* Init GHCB memory pages when running as an SEV-ES guest */
 	sev_es_init_vc_handling();
 
-- 
2.45.2