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[34.124.234.44]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83f1977c494sm14213643b3a.21.2026.05.18.06.13.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 06:13:58 -0700 (PDT) Date: Mon, 18 May 2026 13:13:49 +0000 From: Pranjal Shrivastava To: Samiullah Khawaja 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 v2 03/16] iommu: Implement IOMMU domain preservation Message-ID: References: <20260427175633.1978233-1-skhawaja@google.com> <20260427175633.1978233-4-skhawaja@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260427175633.1978233-4-skhawaja@google.com> On Mon, Apr 27, 2026 at 05:56:20PM +0000, Samiullah Khawaja wrote: > Add IOMMU domain ops that can be implemented by the IOMMU drivers if > they support IOMMU domain preservation across liveupdate. The new IOMMU > domain preserve, unpreserve and restore APIs call these ops to perform > respective live update operations. > > Signed-off-by: Samiullah Khawaja > --- > drivers/iommu/liveupdate.c | 97 ++++++++++++++++++++++++++++++++ > include/linux/iommu-liveupdate.h | 14 +++++ > include/linux/iommu.h | 13 +++++ > 3 files changed, 124 insertions(+) > > diff --git a/drivers/iommu/liveupdate.c b/drivers/iommu/liveupdate.c > index a26099b145c3..f71f14518248 100644 > --- a/drivers/iommu/liveupdate.c > +++ b/drivers/iommu/liveupdate.c > @@ -13,6 +13,9 @@ > #include > #include > > +#define iommu_max_objs_per_page(_array) \ > + ((PAGE_SIZE - sizeof(struct iommu_array_hdr_ser)) / sizeof((_array)->objects[0])) > + > static void *iommu_liveupdate_restore_array(u64 array_phys) > { > struct iommu_array_hdr_ser *array_hdr; > @@ -196,3 +199,97 @@ void iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler) > liveupdate_unregister_flb(handler, &iommu_flb); > } > EXPORT_SYMBOL(iommu_liveupdate_unregister_flb); > + > +static int alloc_object_ser(struct iommu_array_hdr_ser **curr_array_ptr, u64 max_objs) > +{ > + struct iommu_array_hdr_ser *curr_array = *curr_array_ptr; > + struct iommu_array_hdr_ser *next_array; > + > + if (curr_array->nr_objects >= max_objs) { > + next_array = kho_alloc_preserve(PAGE_SIZE); > + if (IS_ERR(next_array)) > + return PTR_ERR(next_array); > + > + curr_array->next_array_phys = virt_to_phys(next_array); > + *curr_array_ptr = next_array; > + curr_array = next_array; > + } > + > + return curr_array->nr_objects++; > +} > + > +static struct iommu_domain_ser *alloc_iommu_domain_ser(struct iommu_flb_obj *flb) > +{ > + int idx; > + > + idx = alloc_object_ser((struct iommu_array_hdr_ser **)&flb->curr_domain_array, Nit: Such type-casts could be brittle and risk strict-aliasing warnings based on the compiler. Since alloc_object_ser only updates the top-level tracking pointer, we can make this much cleaner by changing alloc_object_ser to take a void curr_array_ptr. That way, we can pass (void )&flb->curr_domain_array cleanly without the double-pointer type-punning. Something like: static int alloc_object_ser(void **curr_array_ptr, u64 max_objs) { struct iommu_array_hdr_ser *curr_array = *curr_array_ptr; struct iommu_array_hdr_ser *next_array; ... } and we can pass it as: idx = alloc_object_ser((void **)&flb->curr_domain_array, iommu_max_objs_per_page(flb->curr_domain_array)); > + iommu_max_objs_per_page(flb->curr_domain_array)); > + if (idx < 0) > + return ERR_PTR(idx); > + > + flb->curr_domain_array->objects[idx].hdr.ref_count = 1; > + return &flb->curr_domain_array->objects[idx]; > +} > + > +int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser) > +{ > + struct iommu_domain_ser *domain_ser; > + struct iommu_flb_obj *flb_obj; > + int ret; > + > + if (!domain->ops->preserve) > + return -EOPNOTSUPP; > + > + ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj); > + if (ret) > + return ret; > + > + guard(mutex)(&flb_obj->lock); > + domain_ser = alloc_iommu_domain_ser(flb_obj); > + if (IS_ERR(domain_ser)) > + return PTR_ERR(domain_ser); > + > + ret = domain->ops->preserve(domain, domain_ser); > + if (ret) { > + domain_ser->hdr.deleted = true; Nit: This will become domain_ser->hdr.flags |= IOMMU_SER_FLAG_DELETED; once we convert the bitfields in PATCH 2 to flags. > + return ret; > + } > + > + domain->preserved_state = domain_ser; > + *ser = domain_ser; > + return 0; > +} > +EXPORT_SYMBOL_GPL(iommu_domain_preserve); > + [...] > static inline bool iommu_is_dma_domain(struct iommu_domain *domain) > @@ -752,6 +757,11 @@ struct iommu_ops { > * specific mechanisms. > * @set_pgtable_quirks: Set io page table quirks (IO_PGTABLE_QUIRK_*) > * @free: Release the domain after use. > + * @preserve: Preserve the iommu domain for liveupdate. > + * Returns 0 on success, a negative errno on failure. > + * @unpreserve: Unpreserve the iommu domain that was preserved earlier. > + * @restore: Restore the iommu domain after liveupdate. > + * Returns 0 on success, a negative errno on failure. > */ > struct iommu_domain_ops { > int (*attach_dev)(struct iommu_domain *domain, struct device *dev, > @@ -782,6 +792,9 @@ struct iommu_domain_ops { > unsigned long quirks); > > void (*free)(struct iommu_domain *domain); > + int (*preserve)(struct iommu_domain *domain, struct iommu_domain_ser *ser); > + void (*unpreserve)(struct iommu_domain *domain, struct iommu_domain_ser *ser); > + int (*restore)(struct iommu_domain *domain, struct iommu_domain_ser *ser); Nit: Should we add restore in the patch we implement it? > }; With the above nits, Reviewed-by: Pranjal Shrivastava Thanks, Praan