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Venkataraman" , , "Sean Christopherson" , Paolo Bonzini , , David Woodhouse , Lu Baolu , Alexander Graf , , , , "Saenz Julienne, Nicolas" Subject: [RFC PATCH 01/13] iommufd: Support marking and tracking persistent iommufds Date: Mon, 16 Sep 2024 13:30:50 +0200 Message-ID: <20240916113102.710522-2-jgowans@amazon.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240916113102.710522-1-jgowans@amazon.com> References: <20240916113102.710522-1-jgowans@amazon.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: EX19D041UWB003.ant.amazon.com (10.13.139.176) To EX19D014EUC004.ant.amazon.com (10.252.51.182) Introduce a new iommufd option to mark an iommufd as persistent. For now this allocates it a unique persistent ID from an xarray index and keeps a reference to the domain. This will be used so that at serialisation time the open iommufds can be iterated through and serialised. --- drivers/iommu/iommufd/iommufd_private.h | 1 + drivers/iommu/iommufd/main.c | 47 +++++++++++++++++++++++++ include/uapi/linux/iommufd.h | 5 +++ 3 files changed, 53 insertions(+) diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h index 92efe30a8f0d..b23f7766066c 100644 --- a/drivers/iommu/iommufd/iommufd_private.h +++ b/drivers/iommu/iommufd/iommufd_private.h @@ -28,6 +28,7 @@ struct iommufd_ctx { /* Compatibility with VFIO no iommu */ u8 no_iommu_mode; struct iommufd_ioas *vfio_ioas; + unsigned long persistent_id; }; /* diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c index 83bbd7c5d160..6708ad629b1e 100644 --- a/drivers/iommu/iommufd/main.c +++ b/drivers/iommu/iommufd/main.c @@ -29,6 +29,8 @@ struct iommufd_object_ops { static const struct iommufd_object_ops iommufd_object_ops[]; static struct miscdevice vfio_misc_dev; +static DEFINE_XARRAY_ALLOC(persistent_iommufds); + struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx, size_t size, enum iommufd_object_type type) @@ -287,10 +289,52 @@ static int iommufd_fops_release(struct inode *inode, struct file *filp) break; } WARN_ON(!xa_empty(&ictx->groups)); + + rcu_read_lock(); + if (ictx->persistent_id) + xa_erase(&persistent_iommufds, ictx->persistent_id); + rcu_read_unlock(); kfree(ictx); return 0; } +static int iommufd_option_persistent(struct iommufd_ucmd *ucmd) +{ + unsigned int persistent_id; + int rc; + struct iommu_option *cmd = ucmd->cmd; + struct iommufd_ctx *ictx = ucmd->ictx; + struct xa_limit id_limit = XA_LIMIT(1, UINT_MAX); + + if (cmd->op == IOMMU_OPTION_OP_GET) { + cmd->val64 = ictx->persistent_id; + return 0; + } + + if (cmd->op == IOMMU_OPTION_OP_SET) { + /* + * iommufds can only be marked persistent before they + * have been used for DMA mappings. HWPTs must be known + * to be persistent at creation time. + */ + if (!xa_empty(&ictx->objects)) { + pr_warn("iommufd can only be marked persistented when unused\n"); + return -EFAULT; + } + + rc = xa_alloc(&persistent_iommufds, &persistent_id, ictx, id_limit, GFP_KERNEL_ACCOUNT); + if (rc) { + pr_warn("Unable to keep track of iommufd object\n"); + return rc; + } + + ictx->persistent_id = persistent_id; + cmd->val64 = ictx->persistent_id; + return 0; + } + return -EOPNOTSUPP; +} + static int iommufd_option(struct iommufd_ucmd *ucmd) { struct iommu_option *cmd = ucmd->cmd; @@ -306,6 +350,9 @@ static int iommufd_option(struct iommufd_ucmd *ucmd) case IOMMU_OPTION_HUGE_PAGES: rc = iommufd_ioas_option(ucmd); break; + case IOMMU_OPTION_PERSISTENT: + rc = iommufd_option_persistent(ucmd); + break; default: return -EOPNOTSUPP; } diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h index 4dde745cfb7e..7d8cb242e9b0 100644 --- a/include/uapi/linux/iommufd.h +++ b/include/uapi/linux/iommufd.h @@ -276,10 +276,15 @@ struct iommu_ioas_unmap { * iommu mappings. Value 0 disables combining, everything is mapped to * PAGE_SIZE. This can be useful for benchmarking. This is a per-IOAS * option, the object_id must be the IOAS ID. + * @IOMMU_OPTION_PERSISTENT + * Value 1 sets this iommufd object as a persistent iommufd. Mappings will + * survive across kexec. The returned value is the persistent ID which can + * be used to restore the iommufd after kexec. */ enum iommufd_option { IOMMU_OPTION_RLIMIT_MODE = 0, IOMMU_OPTION_HUGE_PAGES = 1, + IOMMU_OPTION_PERSISTENT = 2, }; /**