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[34.83.136.168]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82c7d1e1960sm554979b3a.3.2026.03.25.13.41.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2026 13:41:50 -0700 (PDT) Date: Wed, 25 Mar 2026 20:41:46 +0000 From: Samiullah Khawaja To: Pranjal Shrivastava Cc: David Woodhouse , Lu Baolu , Joerg Roedel , Will Deacon , Jason Gunthorpe , Robin Murphy , Kevin Tian , Alex Williamson , Shuah Khan , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Saeed Mahameed , Adithya Jayachandran , Parav Pandit , Leon Romanovsky , William Tu , Pratyush Yadav , Pasha Tatashin , David Matlack , Andrew Morton , Chris Li , Vipin Sharma , YiFei Zhu Subject: Re: [PATCH 12/14] iommufd: Add APIs to preserve/unpreserve a vfio cdev Message-ID: References: <20260203220948.2176157-1-skhawaja@google.com> <20260203220948.2176157-13-skhawaja@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Wed, Mar 25, 2026 at 08:24:24PM +0000, Pranjal Shrivastava wrote: >On Tue, Feb 03, 2026 at 10:09:46PM +0000, Samiullah Khawaja wrote: >> Add APIs that can be used to preserve and unpreserve a vfio cdev. Use >> the APIs exported by the IOMMU core to preserve/unpreserve device. Pass >> the LUO preservation token of the attached iommufd into IOMMU preserve >> device API. This establishes the ownership of the device with the >> preserved iommufd. >> >> Signed-off-by: Samiullah Khawaja >> --- >> drivers/iommu/iommufd/device.c | 69 ++++++++++++++++++++++++++++++++++ >> include/linux/iommufd.h | 23 ++++++++++++ >> 2 files changed, 92 insertions(+) >> >> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c >> index 4c842368289f..30cb5218093b 100644 >> --- a/drivers/iommu/iommufd/device.c >> +++ b/drivers/iommu/iommufd/device.c >> @@ -2,6 +2,7 @@ >> /* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES >> */ >> #include >> +#include >> #include >> #include >> #include >> @@ -1661,3 +1662,71 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd) >> iommufd_put_object(ucmd->ictx, &idev->obj); >> return rc; >> } >> + >> +#ifdef CONFIG_IOMMU_LIVEUPDATE >> +int iommufd_device_preserve(struct liveupdate_session *s, >> + struct iommufd_device *idev, >> + u64 *tokenp) >> +{ >> + struct iommufd_group *igroup = idev->igroup; >> + struct iommufd_hwpt_paging *hwpt_paging; >> + struct iommufd_hw_pagetable *hwpt; >> + struct iommufd_attach *attach; >> + int ret; >> + >> + mutex_lock(&igroup->lock); >> + attach = xa_load(&igroup->pasid_attach, IOMMU_NO_PASID); > >By explicitly looking up IOMMU_NO_PASID, we skip any PASID attachments >the device might have. Since PASID live update is NOT supported in this >series, should we check if the pasid_attach xarray contains anything >other than IOMMU_NO_PASID and return -EOPNOTSUPP? > >Otherwise, we silently fail to preserve those domains without informing >the VMM? VMM should be able to preserve the NO_PASID domains even if it has PASID attachments. This is the intended behaviour, I will document it in the uAPI docs. > >> + if (!attach) { >> + ret = -ENOENT; >> + goto out; >> + } >> + >> + hwpt = attach->hwpt; >> + hwpt_paging = find_hwpt_paging(hwpt); >> + if (!hwpt_paging || !hwpt_paging->lu_preserve) { >> + ret = -EINVAL; >> + goto out; >> + } >> + >> + ret = liveupdate_get_token_outgoing(s, idev->ictx->file, tokenp); >> + if (ret) >> + goto out; >> + >> + ret = iommu_preserve_device(hwpt_paging->common.domain, >> + idev->dev, >> + *tokenp); >> +out: >> + mutex_unlock(&igroup->lock); >> + return ret; >> +} >> +EXPORT_SYMBOL_NS_GPL(iommufd_device_preserve, "IOMMUFD"); >> + >> +void iommufd_device_unpreserve(struct liveupdate_session *s, >> + struct iommufd_device *idev, >> + u64 token) >> +{ >> + struct iommufd_group *igroup = idev->igroup; >> + struct iommufd_hwpt_paging *hwpt_paging; >> + struct iommufd_hw_pagetable *hwpt; >> + struct iommufd_attach *attach; >> + >> + mutex_lock(&igroup->lock); >> + attach = xa_load(&igroup->pasid_attach, IOMMU_NO_PASID); >> + if (!attach) { >> + WARN_ON(-ENOENT); > >WARN_ON takes a condition.. if we want this to be printed always, why >not WARN_ON(1, "...") ? What's the significance of having -ENOENT as a >condition? Will update this. > >> + goto out; >> + } >> + >> + hwpt = attach->hwpt; >> + hwpt_paging = find_hwpt_paging(hwpt); >> + if (!hwpt_paging || !hwpt_paging->lu_preserve) { >> + WARN_ON(-EINVAL); > >Same here for -EINVAL? Same here. > >> + goto out; >> + } >> + >> + iommu_unpreserve_device(hwpt_paging->common.domain, idev->dev); >> +out: >> + mutex_unlock(&igroup->lock); >> +} >> +EXPORT_SYMBOL_NS_GPL(iommufd_device_unpreserve, "IOMMUFD"); >> +#endif > >[ ----- >8 ----- ] > >Thanks, >Praan Thanks, Sami