linux-kernel - [PATCH v7 01/10] x86/fred: Provide separate IRQ vs. NMI wrappers for entry from KVM

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Message-ID: <20250612214849.3950094-2-sohil.mehta@intel.com>
Date: Thu, 12 Jun 2025 14:48:40 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Xin Li <xin@...or.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Jacob Pan <jacob.pan@...ux.microsoft.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Sandipan Das <sandipan.das@....com>,
	linux-perf-users@...r.kernel.org,
	linux-edac@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v7 01/10] x86/fred: Provide separate IRQ vs. NMI wrappers for entry from KVM

From: Sean Christopherson <seanjc@...gle.com>

Provide separate wrappers for forwarding IRQs vs NMIs from KVM in
anticipation of adding support for NMI source reporting, which will add
an NMI-only parameter, i.e. will further pollute the current API with a
param that is a hardcoded for one of the two call sites.

Opportunistically tag the non-FRED NMI wrapper __always_inline, as the
compiler could theoretically generate a function call and trigger and a
(completely benign) "leaving noinstr" warning.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
v7: New patch
---
 arch/x86/include/asm/fred.h | 30 ++++++++++++++++++++++--------
 arch/x86/kvm/vmx/vmx.c      |  4 ++--
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h
index 12b34d5b2953..552332ca060c 100644
--- a/arch/x86/include/asm/fred.h
+++ b/arch/x86/include/asm/fred.h
@@ -9,6 +9,7 @@
 #include <linux/const.h>
 
 #include <asm/asm.h>
+#include <asm/irq_vectors.h>
 #include <asm/msr.h>
 #include <asm/trapnr.h>
 
@@ -71,15 +72,27 @@ __visible void fred_entry_from_user(struct pt_regs *regs);
 __visible void fred_entry_from_kernel(struct pt_regs *regs);
 __visible void __fred_entry_from_kvm(struct pt_regs *regs);
 
-/* Can be called from noinstr code, thus __always_inline */
-static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector)
+/* Must be called from noinstr code, thus __always_inline */
+static __always_inline void fred_nmi_from_kvm(void)
 {
 	struct fred_ss ss = {
-		.ss     =__KERNEL_DS,
-		.type   = type,
-		.vector = vector,
-		.nmi    = type == EVENT_TYPE_NMI,
-		.lm     = 1,
+		.ss	= __KERNEL_DS,
+		.type	= EVENT_TYPE_NMI,
+		.vector	= NMI_VECTOR,
+		.nmi	= true,
+		.lm	= 1,
+	};
+
+	asm_fred_entry_from_kvm(ss);
+}
+
+static inline void fred_irq_from_kvm(unsigned int vector)
+{
+	struct fred_ss ss = {
+		.ss	= __KERNEL_DS,
+		.type	= EVENT_TYPE_EXTINT,
+		.vector	= vector,
+		.lm	= 1,
 	};
 
 	asm_fred_entry_from_kvm(ss);
@@ -110,7 +123,8 @@ static __always_inline unsigned long fred_event_data(struct pt_regs *regs) { ret
 static inline void cpu_init_fred_exceptions(void) { }
 static inline void cpu_init_fred_rsps(void) { }
 static inline void fred_complete_exception_setup(void) { }
-static inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) { }
+static __always_inline void fred_nmi_from_kvm(void) { }
+static inline void fred_irq_from_kvm(unsigned int vector) { }
 static inline void fred_sync_rsp0(unsigned long rsp0) { }
 static inline void fred_update_rsp0(void) { }
 #endif /* CONFIG_X86_FRED */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4953846cb30d..8183886eda3d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6991,7 +6991,7 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu,
 
 	kvm_before_interrupt(vcpu, KVM_HANDLING_IRQ);
 	if (cpu_feature_enabled(X86_FEATURE_FRED))
-		fred_entry_from_kvm(EVENT_TYPE_EXTINT, vector);
+		fred_irq_from_kvm(vector);
 	else
 		vmx_do_interrupt_irqoff(gate_offset((gate_desc *)host_idt_base + vector));
 	kvm_after_interrupt(vcpu);
@@ -7264,7 +7264,7 @@ noinstr void vmx_handle_nmi(struct kvm_vcpu *vcpu)
 
 	kvm_before_interrupt(vcpu, KVM_HANDLING_NMI);
 	if (cpu_feature_enabled(X86_FEATURE_FRED))
-		fred_entry_from_kvm(EVENT_TYPE_NMI, NMI_VECTOR);
+		fred_nmi_from_kvm();
 	else
 		vmx_do_nmi_irqoff();
 	kvm_after_interrupt(vcpu);
-- 
2.43.0