linux-kernel - RE: [PATCH v3 01/15] iommu/vt-d: Handle race between registration and device probe

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Date:   Thu, 7 Jul 2022 06:51:48 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Robin Murphy <robin.murphy@....com>,
        "joro@...tes.org" <joro@...tes.org>
CC:     "will@...nel.org" <will@...nel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "vasant.hegde@....com" <vasant.hegde@....com>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "gerald.schaefer@...ux.ibm.com" <gerald.schaefer@...ux.ibm.com>,
        "schnelle@...ux.ibm.com" <schnelle@...ux.ibm.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 01/15] iommu/vt-d: Handle race between registration and
 device probe

> From: Robin Murphy <robin.murphy@....com>
> Sent: Wednesday, July 6, 2022 1:08 AM
> 
> Currently we rely on registering all our instances before initially
> allowing any .probe_device calls via bus_set_iommu(). In preparation for
> phasing out the latter, make sure we won't inadvertently return success
> for a device associated with a known but not yet registered instance,
> otherwise we'll run straight into iommu_group_get_for_dev() trying to
> use NULL ops.
> 
> That also highlights an issue with intel_iommu_get_resv_regions() taking
> dmar_global_lock from within a section where intel_iommu_init() already
> holds it, which already exists via probe_acpi_namespace_devices() when
> an ANDD device is probed, but gets more obvious with the upcoming change
> to iommu_device_register(). Since they are both read locks it manages
> not to deadlock in practice, so I'm leaving it here for someone with
> more confidence to tackle a larger rework of the locking.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>