From: Jason Gunthorpe <jgg@nvidia.com>
To: Nicolin Chen <nicolinc@nvidia.com>
Cc: Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
joro@8bytes.org, Kevin Tian <kevin.tian@intel.com>,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/3] iommufd/viommu: Publish a vDEVICE only after vdevice_init() succeeds
Date: Mon, 6 Jul 2026 14:23:56 -0300 [thread overview]
Message-ID: <20260706172356.GB118313@nvidia.com> (raw)
In-Reply-To: <1e05999347f4bf583edbc6a1312c857d5548708c.1783311134.git.nicolinc@nvidia.com>
On Sun, Jul 05, 2026 at 10:36:10PM -0700, Nicolin Chen wrote:
> @@ -218,18 +218,28 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
> */
> idev->vdev = vdev;
>
> - curr = xa_cmpxchg(&viommu->vdevs, virt_id, NULL, vdev, GFP_KERNEL);
> - if (curr) {
> - rc = xa_err(curr) ?: -EEXIST;
> + /*
> + * Reserve the slot with a zero entry (reads back as NULL) until the
> + * vdevice_init() op accepts the vDEVICE. Only the xa_* helpers hide a
> + * reserved entry, so never use a raw xas_* iterator on this xarray.
> + */
> + rc = xa_insert(&viommu->vdevs, virt_id, NULL, GFP_KERNEL);
> + if (rc) {
Why xa_insert() not xa_reserve() ?
Jason
next prev parent reply other threads:[~2026-07-06 17:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-06 5:36 [PATCH v2 0/3] iommufd: Fix vDEVICE allocation lifecycle bugs Nicolin Chen
2026-07-06 5:36 ` [PATCH v2 1/3] iommufd/viommu: Release the igroup lock on the vdevice_size error path Nicolin Chen
2026-07-06 5:36 ` [PATCH v2 2/3] iommufd/viommu: Publish a vDEVICE only after vdevice_init() succeeds Nicolin Chen
2026-07-06 17:23 ` Jason Gunthorpe [this message]
2026-07-06 18:05 ` Nicolin Chen
2026-07-06 19:47 ` Jason Gunthorpe
2026-07-06 5:36 ` [PATCH v2 3/3] iommu/arm-smmu-v3-iommufd: Require exactly one Stream ID for a vDEVICE Nicolin Chen
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