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[v9,20/36] x86/fred: Add a NMI entry stub for FRED

Message ID 20230731063317.3720-21-xin3.li@intel.com (mailing list archive)
State New, archived
Headers show
Series x86: enable FRED for x86-64 | expand

Commit Message

Li, Xin3 July 31, 2023, 6:33 a.m. UTC 
From: "H. Peter Anvin (Intel)" <hpa@zytor.com>

On a FRED system, NMIs nest both with themselves and faults, transient
information is saved into the stack frame, and NMI unblocking only
happens when the stack frame indicates that so should happen.

Thus, the NMI entry stub for FRED is really quite small...

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
 arch/x86/include/asm/fred.h |  1 +
 arch/x86/kernel/nmi.c       | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h
index ad7b79130b1e..2a7c47dfd733 100644
--- a/arch/x86/include/asm/fred.h
+++ b/arch/x86/include/asm/fred.h
@@ -112,6 +112,7 @@  static __always_inline unsigned long fred_event_data(struct pt_regs *regs)
 
 typedef DECLARE_FRED_HANDLER((*fred_handler));
 
+DECLARE_FRED_HANDLER(fred_exc_nmi);
 DECLARE_FRED_HANDLER(fred_exc_debug);
 DECLARE_FRED_HANDLER(fred_exc_page_fault);
 
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index a0c551846b35..f803e2bcd024 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -34,6 +34,7 @@ 
 #include <asm/cache.h>
 #include <asm/nospec-branch.h>
 #include <asm/sev.h>
+#include <asm/fred.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/nmi.h>
@@ -643,6 +644,24 @@  void nmi_backtrace_stall_check(const struct cpumask *btp)
 
 #endif
 
+#ifdef CONFIG_X86_FRED
+DEFINE_FRED_HANDLER(fred_exc_nmi)
+{
+	/*
+	 * With FRED, CR2 and DR6 are pushed atomically on faults,
+	 * so we don't have to worry about saving and restoring them.
+	 * Breakpoint faults nest, so assume it is OK to leave DR7
+	 * enabled.
+	 */
+	irqentry_state_t irq_state = irqentry_nmi_enter(regs);
+
+	inc_irq_stat(__nmi_count);
+	default_do_nmi(regs);
+
+	irqentry_nmi_exit(regs, irq_state);
+}
+#endif
+
 void stop_nmi(void)
 {
 	ignore_nmis++;