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Message-ID: <b05a1dd0-9692-4bf7-8fa0-0b3857178d1b@linux.intel.com>
Date: Thu, 4 Dec 2025 14:43:39 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Samiullah Khawaja <skhawaja@...gle.com>,
David Woodhouse <dwmw2@...radead.org>, Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>, Pasha Tatashin <pasha.tatashin@...een.com>,
Jason Gunthorpe <jgg@...pe.ca>, iommu@...ts.linux.dev
Cc: Robin Murphy <robin.murphy@....com>, Pratyush Yadav
<pratyush@...nel.org>, Kevin Tian <kevin.tian@...el.com>,
Alex Williamson <alex@...zbot.org>, linux-kernel@...r.kernel.org,
Saeed Mahameed <saeedm@...dia.com>,
Adithya Jayachandran <ajayachandra@...dia.com>,
Parav Pandit <parav@...dia.com>, Leon Romanovsky <leonro@...dia.com>,
William Tu <witu@...dia.com>, Vipin Sharma <vipinsh@...gle.com>,
dmatlack@...gle.com, YiFei Zhu <zhuyifei@...gle.com>,
Chris Li <chrisl@...nel.org>, praan@...gle.com
Subject: Re: [RFC PATCH v2 24/32] iommu/vt-d: restore state of the preserved
IOMMU
On 12/3/25 07:02, Samiullah Khawaja wrote:
> During boot fetch the preserved state of IOMMU unit and if found then
> restore the state. Reuse the root_table that was preserved in the
> previous kernel.
>
> Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
> ---
> drivers/iommu/intel/iommu.c | 30 ++++++++++++++++++++++++------
> drivers/iommu/intel/iommu.h | 2 ++
> drivers/iommu/intel/liveupdate.c | 30 ++++++++++++++++++++++++++++++
> 3 files changed, 56 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 84fef81ecf4d..888351f91918 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -224,12 +224,12 @@ static void clear_translation_pre_enabled(struct intel_iommu *iommu)
> iommu->flags &= ~VTD_FLAG_TRANS_PRE_ENABLED;
> }
>
> -static void init_translation_status(struct intel_iommu *iommu)
> +static void init_translation_status(struct intel_iommu *iommu, bool restoring)
> {
> u32 gsts;
>
> gsts = readl(iommu->reg + DMAR_GSTS_REG);
> - if (gsts & DMA_GSTS_TES)
> + if (!restoring && (gsts & DMA_GSTS_TES))
> iommu->flags |= VTD_FLAG_TRANS_PRE_ENABLED;
> }
>
> @@ -672,10 +672,18 @@ void dmar_fault_dump_ptes(struct intel_iommu *iommu, u16 source_id,
> #endif
>
> /* iommu handling */
> -static int iommu_alloc_root_entry(struct intel_iommu *iommu)
> +static int iommu_alloc_root_entry(struct intel_iommu *iommu, struct iommu_ser *restored_state)
> {
> struct root_entry *root;
>
> +#if CONFIG_LIVEUPDATE
nit: Is it possible to hide the "IS_ENABLED(CONFIG_LIVEUPDATE)" and "#if
CONFIG_LIVEUPDATE" checks within the header files?
> + if (restored_state) {
> + intel_iommu_liveupdate_restore_root_table(iommu, restored_state);
> + /* Should not be needed since the entries are already cleaned in last kernel. */
> + __iommu_flush_cache(iommu, iommu->root_entry, ROOT_SIZE);
> + return 0;
> + }
> +#endif
> root = iommu_alloc_pages_node_sz(iommu->node, GFP_ATOMIC, SZ_4K);
> if (!root) {
> pr_err("Allocating root entry for %s failed\n",
> @@ -1616,6 +1624,7 @@ static int copy_translation_tables(struct intel_iommu *iommu)
>
> static int __init init_dmars(void)
> {
> + struct iommu_ser *iommu_ser = NULL;
> struct dmar_drhd_unit *drhd;
> struct intel_iommu *iommu;
> int ret;
> @@ -1638,8 +1647,12 @@ static int __init init_dmars(void)
> intel_pasid_max_id);
> }
>
> +#if IS_ENABLED(CONFIG_LIVEUPDATE)
> + iommu_ser = iommu_get_preserved_data(iommu->reg_phys, IOMMU_INTEL);
> +#endif
> +
> intel_iommu_init_qi(iommu);
> - init_translation_status(iommu);
> + init_translation_status(iommu, !!iommu_ser);
>
> if (translation_pre_enabled(iommu) && !is_kdump_kernel()) {
> iommu_disable_translation(iommu);
> @@ -1653,7 +1666,7 @@ static int __init init_dmars(void)
> * we could share the same root & context tables
> * among all IOMMU's. Need to Split it later.
> */
> - ret = iommu_alloc_root_entry(iommu);
> + ret = iommu_alloc_root_entry(iommu, iommu_ser);
> if (ret)
> goto free_iommu;
>
> @@ -2112,6 +2125,7 @@ int dmar_parse_one_satc(struct acpi_dmar_header *hdr, void *arg)
> static int intel_iommu_add(struct dmar_drhd_unit *dmaru)
> {
> struct intel_iommu *iommu = dmaru->iommu;
> + struct iommu_ser *iommu_ser = NULL;
> int ret;
>
> /*
> @@ -2120,7 +2134,11 @@ static int intel_iommu_add(struct dmar_drhd_unit *dmaru)
> if (iommu->gcmd & DMA_GCMD_TE)
> iommu_disable_translation(iommu);
>
> - ret = iommu_alloc_root_entry(iommu);
> +#if IS_ENABLED(CONFIG_LIVEUPDATE)
> + iommu_ser = iommu_get_preserved_data(iommu->reg_phys, IOMMU_INTEL);
> +#endif
> +
> + ret = iommu_alloc_root_entry(iommu, iommu_ser);
> if (ret)
> goto out;
>
> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index 1eb60ce1300f..b0c56e27f167 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -1283,6 +1283,8 @@ int intel_iommu_preserve_device(struct device *dev, struct device_ser *device_se
> void intel_iommu_unpreserve_device(struct device *dev, struct device_ser *device_ser);
> int intel_iommu_preserve(struct iommu_device *iommu, struct iommu_ser *iommu_ser);
> void intel_iommu_unpreserve(struct iommu_device *iommu, struct iommu_ser *iommu_ser);
> +void intel_iommu_liveupdate_restore_root_table(struct intel_iommu *iommu,
> + struct iommu_ser *iommu_ser);
> bool intel_iommu_liveupdate_clear_context_entries(struct intel_iommu *iommu);
> #endif
>
> diff --git a/drivers/iommu/intel/liveupdate.c b/drivers/iommu/intel/liveupdate.c
> index 3f8c7f15bc36..140887187084 100644
> --- a/drivers/iommu/intel/liveupdate.c
> +++ b/drivers/iommu/intel/liveupdate.c
> @@ -73,6 +73,36 @@ static int preserve_iommu_context(struct intel_iommu *iommu)
> return ret;
> }
>
> +static void restore_iommu_context(struct intel_iommu *iommu)
> +{
> + struct context_entry *context;
> + int i;
> +
> + for (i = 0; i < ROOT_ENTRY_NR; i++) {
> + context = iommu_context_addr(iommu, i, 0, 0);
> + if (context)
> + BUG_ON(!kho_restore_folio(virt_to_phys(context)));
> +
> + if (!sm_supported(iommu))
> + continue;
> +
> + context = iommu_context_addr(iommu, i, 0x80, 0);
> + if (context)
> + BUG_ON(!kho_restore_folio(virt_to_phys(context)));
> + }
> +}
> +
> +void intel_iommu_liveupdate_restore_root_table(struct intel_iommu *iommu,
> + struct iommu_ser *iommu_ser)
> +{
> + BUG_ON(!kho_restore_folio(iommu_ser->intel.root_table));
> + iommu->root_entry = __va(iommu_ser->intel.root_table);
> +
> + restore_iommu_context(iommu);
> + pr_info("Restored IOMMU[0x%llx] Root Table at: 0x%llx\n",
> + iommu->reg_phys, iommu_ser->intel.root_table);
> +}
> +
> int intel_iommu_preserve_device(struct device *dev, struct device_ser *device_ser)
> {
> struct device_domain_info *info = dev_iommu_priv_get(dev);
Thanks,
baolu
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