linux-kernel - [RFC 10/11] iommu/arm-smmu: Do not advertise IOMMU_CAP_INTR

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Message-Id: <1475009318-2617-11-git-send-email-eric.auger@redhat.com>
Date:   Tue, 27 Sep 2016 20:48:37 +0000
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger@...hat.com, eric.auger.pro@...il.com,
        christoffer.dall@...aro.org, marc.zyngier@....com,
        robin.murphy@....com, alex.williamson@...hat.com,
        will.deacon@....com, joro@...tes.org, tglx@...utronix.de,
        jason@...edaemon.net, linux-arm-kernel@...ts.infradead.org
Cc:     kvm@...r.kernel.org, drjones@...hat.com,
        linux-kernel@...r.kernel.org, Bharat.Bhushan@...escale.com,
        pranav.sawargaonkar@...il.com, p.fedin@...sung.com,
        iommu@...ts.linux-foundation.org, Jean-Philippe.Brucker@....com,
        yehuday@...vell.com, Manish.Jaggi@...iumnetworks.com
Subject: [RFC 10/11] iommu/arm-smmu: Do not advertise IOMMU_CAP_INTR_REMAP

Do not advertise IOMMU_CAP_INTR_REMAP for arm-smmu(-v3). Indeed the
irq_remapping capability is abstracted on irqchip side for ARM as
opposed to Intel IOMMU featuring IRQ remapping HW.

So for the time being assignement is considered as unsafe on ARM,
until we get an accurate description of whether the MSI controllers
are downstream to smmus.

This commit affects platform and PCIe device assignment use cases.

Signed-off-by: Eric Auger <eric.auger@...hat.com>

---
---
 drivers/iommu/arm-smmu-v3.c | 3 ++-
 drivers/iommu/arm-smmu.c    | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index e825679..c86ba84 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1371,7 +1371,8 @@ static bool arm_smmu_capable(enum iommu_cap cap)
 	case IOMMU_CAP_CACHE_COHERENCY:
 		return true;
 	case IOMMU_CAP_INTR_REMAP:
-		return true; /* MSIs are just memory writes */
+		/* interrupt translation handled at MSI controller level */
+		return false;
 	case IOMMU_CAP_NOEXEC:
 		return true;
 	default:
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 707c09b..7af1dd0 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1359,7 +1359,8 @@ static bool arm_smmu_capable(enum iommu_cap cap)
 		 */
 		return true;
 	case IOMMU_CAP_INTR_REMAP:
-		return true; /* MSIs are just memory writes */
+		/* interrupt translation handled at MSI controller level */
+		return false;
 	case IOMMU_CAP_NOEXEC:
 		return true;
 	default:
-- 
1.9.1