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Schoenherr" , Usama Arif , Anthony Yznaga , Stanislav Kinsburskii , , , Subject: [RFC 08/18] iommu: Add allocator for pgtables from persistent region Date: Mon, 5 Feb 2024 12:01:53 +0000 Message-ID: <20240205120203.60312-9-jgowans@amazon.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240205120203.60312-1-jgowans@amazon.com> References: <20240205120203.60312-1-jgowans@amazon.com> MIME-Version: 1.0 X-Originating-IP: [172.19.112.191] X-ClientProxiedBy: EX19D033UWC001.ant.amazon.com (10.13.139.218) To EX19D014EUC004.ant.amazon.com (10.252.51.182) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240205_040402_875405_31C8E22C X-CRM114-Status: GOOD ( 20.89 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org The specific IOMMU drivers will need to ability to allocate pages from a pkernfs IOMMU pgtable file for their pgtables. Also, the IOMMU drivers will need to ability to consistent get the same page for the root PGD page - add a specific function to get this PGD "root" page. This is different to allocating regular pgtable pages because the exact same page needs to be *restored* after kexec into the pgd pointer on the IOMMU domain struct. To support this sort of allocation the pkernfs region is treated as an array of 512 4 KiB pages, the first of which is an allocation bitmap. --- drivers/iommu/Makefile | 1 + drivers/iommu/pgtable_alloc.c | 36 +++++++++++++++++++++++++++++++++++ drivers/iommu/pgtable_alloc.h | 9 +++++++++ 3 files changed, 46 insertions(+) create mode 100644 drivers/iommu/pgtable_alloc.c create mode 100644 drivers/iommu/pgtable_alloc.h diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile index 769e43d780ce..cadebabe9581 100644 --- a/drivers/iommu/Makefile +++ b/drivers/iommu/Makefile @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 obj-y += amd/ intel/ arm/ iommufd/ +obj-y += pgtable_alloc.o obj-$(CONFIG_IOMMU_API) += iommu.o obj-$(CONFIG_IOMMU_API) += iommu-traces.o obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o diff --git a/drivers/iommu/pgtable_alloc.c b/drivers/iommu/pgtable_alloc.c new file mode 100644 index 000000000000..f0c2e12f8a8b --- /dev/null +++ b/drivers/iommu/pgtable_alloc.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include "pgtable_alloc.h" +#include + +/* + * The first 4 KiB is the bitmap - set the first bit in the bitmap. + * Scan bitmap to find next free bits - it's next free page. + */ + +void iommu_alloc_page_from_region(struct pkernfs_region *region, void **vaddr, unsigned long *paddr) +{ + int page_idx; + + page_idx = bitmap_find_free_region(region->vaddr, 512, 0); + *vaddr = region->vaddr + (page_idx << PAGE_SHIFT); + if (paddr) + *paddr = region->paddr + (page_idx << PAGE_SHIFT); +} + + +void *pgtable_get_root_page(struct pkernfs_region *region, bool liveupdate) +{ + /* + * The page immediately after the bitmap is the root page. + * It would be wrong for the page to be allocated if we're + * NOT doing a liveupdate, or for a liveupdate to happen + * with no allocated page. Detect this mismatch. + */ + if (test_bit(1, region->vaddr) ^ liveupdate) { + pr_err("%sdoing a liveupdate but root pg bit incorrect", + liveupdate ? "" : "NOT "); + } + set_bit(1, region->vaddr); + return region->vaddr + PAGE_SIZE; +} diff --git a/drivers/iommu/pgtable_alloc.h b/drivers/iommu/pgtable_alloc.h new file mode 100644 index 000000000000..c1666a7be3d3 --- /dev/null +++ b/drivers/iommu/pgtable_alloc.h @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +#include +#include + +void iommu_alloc_page_from_region(struct pkernfs_region *region, + void **vaddr, unsigned long *paddr); + +void *pgtable_get_root_page(struct pkernfs_region *region, bool liveupdate); -- 2.40.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec