[tip: x86/fred] x86/fred: Invoke FRED initialization code to enable FRED

tip-bot2 for H. Peter Anvin (Intel)
2024-01-31T21:14:41Z

Commit-ID: 208d8c79fd0f155bce1b23d8d78926653f7603b7
Gitweb: https://git.kernel.org/tip/208d8c79fd0f155bce1b23d8d78926653f7603b7
Author: H. Peter Anvin (Intel) <hpa@zytor.com>
AuthorDate: Tue, 05 Dec 2023 02:50:24 -08:00
Committer: Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Wed, 31 Jan 2024 22:03:36 +01:00

x86/fred: Invoke FRED initialization code to enable FRED

Let cpu_init_exception_handling() call cpu_init_fred_exceptions() to
initialize FRED. However if FRED is unavailable or disabled, it falls
back to set up TSS IST and initialize IDT.

Co-developed-by: Xin Li <xin3.li@intel.com>
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-36-xin3.li@intel.com
---
arch/x86/kernel/cpu/common.c | 22 +++++++++++++++++-----
arch/x86/kernel/irqinit.c | 7 ++++++-
arch/x86/kernel/traps.c | 5 ++++-
3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4f5e4aa..cf82e31 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -61,6 +61,7 @@
#include <asm/microcode.h>
#include <asm/intel-family.h>
#include <asm/cpu_device_id.h>
+#include <asm/fred.h>
#include <asm/uv/uv.h>
#include <asm/ia32.h>
#include <asm/set_memory.h>
@@ -2107,7 +2108,15 @@ void syscall_init(void)
/* The default user and kernel segments */
wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);

- idt_syscall_init();
+ /*
+ * Except the IA32_STAR MSR, there is NO need to setup SYSCALL and
+ * SYSENTER MSRs for FRED, because FRED uses the ring 3 FRED
+ * entrypoint for SYSCALL and SYSENTER, and ERETU is the only legit
+ * instruction to return to ring 3 (both sysexit and sysret cause
+ * #UD when FRED is enabled).
+ */
+ if (!cpu_feature_enabled(X86_FEATURE_FRED))
+ idt_syscall_init();
}

#else /* CONFIG_X86_64 */
@@ -2213,8 +2222,9 @@ void cpu_init_exception_handling(void)
/* paranoid_entry() gets the CPU number from the GDT */
setup_getcpu(cpu);

- /* IST vectors need TSS to be set up. */
- tss_setup_ist(tss);
+ /* For IDT mode, IST vectors need to be set in TSS. */
+ if (!cpu_feature_enabled(X86_FEATURE_FRED))
+ tss_setup_ist(tss);
tss_setup_io_bitmap(tss);
set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);

@@ -2223,8 +2233,10 @@ void cpu_init_exception_handling(void)
/* GHCB needs to be setup to handle #VC. */
setup_ghcb();

- /* Finally load the IDT */
- load_current_idt();
+ if (cpu_feature_enabled(X86_FEATURE_FRED))
+ cpu_init_fred_exceptions();
+ else
+ load_current_idt();
}

/*
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index c683666..f79c5ed 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -28,6 +28,7 @@
#include <asm/setup.h>
#include <asm/i8259.h>
#include <asm/traps.h>
+#include <asm/fred.h>
#include <asm/prom.h>

/*
@@ -96,7 +97,11 @@ void __init native_init_IRQ(void)
/* Execute any quirks before the call gates are initialised: */
x86_init.irqs.pre_vector_init();

- idt_setup_apic_and_irq_gates();
+ if (cpu_feature_enabled(X86_FEATURE_FRED))
+ fred_complete_exception_setup();
+ else
+ idt_setup_apic_and_irq_gates();
+
lapic_assign_system_vectors();

if (!acpi_ioapic && !of_ioapic && nr_legacy_irqs()) {
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 1b19a17..6cb31df 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1438,7 +1438,10 @@ void __init trap_init(void)

/* Initialize TSS before setting up traps so ISTs work */
cpu_init_exception_handling();
+
/* Setup traps as cpu_init() might #GP */
- idt_setup_traps();
+ if (!cpu_feature_enabled(X86_FEATURE_FRED))
+ idt_setup_traps();
+
cpu_init();
}