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x86/fred: Install system vector handlers even if FRED isn't fully enabled

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Install the system vector IRQ handlers for FRED even if FRED isn't fully
enabled in hardware.  This will allow KVM to use the FRED IRQ path even
on non-FRED hardware, which in turn will eliminate a non-CFI indirect CALL
(KVM currently invokes the IRQ handler via an IDT lookup on the vector).

[sean: extract from diff, drop stub, write changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250714103441.121251108@infradead.org
This commit is contained in:
Sean Christopherson 2025-05-02 07:24:01 -07:00 committed by Peter Zijlstra
parent c8ed081264
commit 2d1435b742
2 changed files with 6 additions and 9 deletions
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9
arch/x86/include/asm/idtentry.h
View File

@ -460,17 +460,12 @@ __visible noinstr void func(struct pt_regs *regs, \
#endif
void idt_install_sysvec(unsigned int n, const void *function);
#ifdef CONFIG_X86_FRED
void fred_install_sysvec(unsigned int vector, const idtentry_t function);
#else
static inline void fred_install_sysvec(unsigned int vector, const idtentry_t function) { }
#endif
#define sysvec_install(vector, function) { \
if (cpu_feature_enabled(X86_FEATURE_FRED)) \
if (IS_ENABLED(CONFIG_X86_FRED)) \
fred_install_sysvec(vector, function); \
else \
if (!cpu_feature_enabled(X86_FEATURE_FRED)) \
idt_install_sysvec(vector, asm_##function); \
}

6
arch/x86/kernel/irqinit.c
View File

@ -97,9 +97,11 @@ void __init native_init_IRQ(void)
/* Execute any quirks before the call gates are initialised: */
x86_init.irqs.pre_vector_init();
if (cpu_feature_enabled(X86_FEATURE_FRED))
/* FRED's IRQ path may be used even if FRED isn't fully enabled. */
if (IS_ENABLED(CONFIG_X86_FRED))
fred_complete_exception_setup();
else
if (!cpu_feature_enabled(X86_FEATURE_FRED))
idt_setup_apic_and_irq_gates();
lapic_assign_system_vectors();