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Message-ID: <CAAywjhR=+=3KKQbmEaj0htyzru36reKd8PRse23XMBBfq1myrQ@mail.gmail.com>
Date: Thu, 4 Dec 2025 09:55:19 -0800
From: Samiullah Khawaja <skhawaja@...gle.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: 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,
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 Wed, Dec 3, 2025 at 10:48 PM Baolu Lu <baolu.lu@...ux.intel.com> wrote:
>
> 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?
Thanks for pointing this out.
Yes I think this one can be moved into the header file. I will
evaluate/check all of them and move the ones that can be moved.
>
> > + 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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