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From:   Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To:     Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org
Cc:     Tony Luck <tony.luck@intel.com>, Andi Kleen <ak@linux.intel.com>,
        Stephane Eranian <eranian@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Joerg Roedel <joro@8bytes.org>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Ricardo Neri <ricardo.neri@intel.com>,
        iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Subject: [PATCH v6 05/29] x86/apic/vector: Do not allocate vectors for NMIs
Date:   Thu,  5 May 2022 16:59:44 -0700
Message-Id: <20220506000008.30892-6-ricardo.neri-calderon@linux.intel.com>
In-Reply-To: <20220506000008.30892-1-ricardo.neri-calderon@linux.intel.com>
References: <20220506000008.30892-1-ricardo.neri-calderon@linux.intel.com>
Precedence: bulk

Vectors are meaningless when allocating IRQs with NMI as the delivery mode.
In such case, skip the reservation of IRQ vectors. Do it in the lowest-
level functions where the actual IRQ reservation takes place.

Since NMIs target specific CPUs, keep the functionality to find the best
CPU.

Cc: Andi Kleen <ak@linux.intel.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: iommu@lists.linux-foundation.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: x86@kernel.org
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v5:
 * Introduced this patch.

Changes since v4:
 * N/A

Changes since v3:
 * N/A

Changes since v2:
 * N/A

Changes since v1:
 * N/A
---
 arch/x86/kernel/apic/vector.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 838e220e8860..11f881f45cec 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -245,11 +245,20 @@ assign_vector_locked(struct irq_data *irqd, const struct cpumask *dest)
 	if (apicd->move_in_progress || !hlist_unhashed(&apicd->clist))
 		return -EBUSY;
 
+	if (apicd->hw_irq_cfg.delivery_mode == APIC_DELIVERY_MODE_NMI) {
+		cpu = irq_matrix_find_best_cpu(vector_matrix, dest);
+		apicd->cpu = cpu;
+		vector = 0;
+		goto no_vector;
+	}
+
 	vector = irq_matrix_alloc(vector_matrix, dest, resvd, &cpu);
 	trace_vector_alloc(irqd->irq, vector, resvd, vector);
 	if (vector < 0)
 		return vector;
 	apic_update_vector(irqd, vector, cpu);
+
+no_vector:
 	apic_update_irq_cfg(irqd, vector, cpu);
 
 	return 0;
@@ -321,12 +330,22 @@ assign_managed_vector(struct irq_data *irqd, const struct cpumask *dest)
 	/* set_affinity might call here for nothing */
 	if (apicd->vector && cpumask_test_cpu(apicd->cpu, vector_searchmask))
 		return 0;
+
+	if (apicd->hw_irq_cfg.delivery_mode == APIC_DELIVERY_MODE_NMI) {
+		cpu = irq_matrix_find_best_cpu_managed(vector_matrix, dest);
+		apicd->cpu = cpu;
+		vector = 0;
+		goto no_vector;
+	}
+
 	vector = irq_matrix_alloc_managed(vector_matrix, vector_searchmask,
 					  &cpu);
 	trace_vector_alloc_managed(irqd->irq, vector, vector);
 	if (vector < 0)
 		return vector;
 	apic_update_vector(irqd, vector, cpu);
+
+no_vector:
 	apic_update_irq_cfg(irqd, vector, cpu);
 	return 0;
 }
@@ -376,6 +395,10 @@ static void x86_vector_deactivate(struct irq_domain *dom, struct irq_data *irqd)
 	if (apicd->has_reserved)
 		return;
 
+	/* NMI IRQs do not have associated vectors; nothing to do. */
+	if (apicd->hw_irq_cfg.delivery_mode == APIC_DELIVERY_MODE_NMI)
+		return;
+
 	raw_spin_lock_irqsave(&vector_lock, flags);
 	clear_irq_vector(irqd);
 	if (apicd->can_reserve)
@@ -472,6 +495,10 @@ static void vector_free_reserved_and_managed(struct irq_data *irqd)
 	trace_vector_teardown(irqd->irq, apicd->is_managed,
 			      apicd->has_reserved);
 
+	/* NMI IRQs do not have associated vectors; nothing to do. */
+	if (apicd->hw_irq_cfg.delivery_mode == APIC_DELIVERY_MODE_NMI)
+		return;
+
 	if (apicd->has_reserved)
 		irq_matrix_remove_reserved(vector_matrix);
 	if (apicd->is_managed)
-- 
2.17.1