linux-kernel - [PATCH v7 06/24] iommu/vt-d: Clear the redirection hint when the destination mode is physical

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Message-Id: <20230301234753.28582-7-ricardo.neri-calderon@linux.intel.com>
Date:   Wed,  1 Mar 2023 15:47:35 -0800
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Len Brown <len.brown@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        linuxppc-dev@...ts.ozlabs.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v7 06/24] iommu/vt-d: Clear the redirection hint when the destination mode is physical

When the destination mode of an interrupt is physical APICID, the interrupt
is delivered only to the single CPU of which the physical APICID is
specified in the destination ID field. The redirection hint is meaningless.

Furthermore, on certain processors, the IOMMU does not deliver the
interrupt when the delivery mode is NMI, the redirection hint is set, and
the destination mode is physical. Clearing the redirection hint ensures
that the NMI is delivered.

Cc: Andi Kleen <ak@...ux.intel.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@...el.com>
Cc: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: iommu@...ts.linux-foundation.org
Cc: linuxppc-dev@...ts.ozlabs.org
Suggested-by: Ashok Raj <ashok.raj@...el.com>
Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
---
Changes since v6:
 * None

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
---
 drivers/iommu/intel/irq_remapping.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index 6d01fa078c36..2d68f94ae0ee 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -1123,7 +1123,17 @@ static void prepare_irte(struct irte *irte, int vector, unsigned int dest)
 	irte->dlvry_mode = apic->delivery_mode;
 	irte->vector = vector;
 	irte->dest_id = IRTE_DEST(dest);
-	irte->redir_hint = 1;
+
+	/*
+	 * When using the destination mode of physical APICID, only the
+	 * processor specified in @dest receives the interrupt. The redirection
+	 * hint is meaningless.
+	 *
+	 * Furthermore, on some processors, NMIs with physical delivery mode
+	 * and the redirection hint set are delivered as regular interrupts
+	 * or not delivered at all.
+	 */
+	irte->redir_hint = apic->dest_mode_logical;
 }
 
 struct irq_remap_ops intel_irq_remap_ops = {
-- 
2.25.1