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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Jonathan Corbet , Jesper Dangaard Brouer , Ilias Apalodimas , Willem de Bruijn , Kuniyuki Iwashima , Joshua Washington , Harshitha Ramamurthy , Saeed Mahameed , Tariq Toukan , Tony Nguyen , Przemek Kitszel , Alexander Lobakin , Michael Chan , Pavan Chebbi , iommu@lists.linux.dev, netdev@vger.kernel.org, linux-mm@kvack.org, driver-core@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Luigi Rizzo Content-Type: text/plain; charset="UTF-8" In Confidential Computing (CoCo) guests (AMD SEV-SNP, Intel TDX, ARM CCA), guest memory is private/encrypted by default and DMA buffers must be converted to shared/decrypted in the host page tables before a device can access them. Similarly, in preemptible VMs, IO-accessible memory may need to be pinned in the host on allocation and unpinned on release. Doing these conversions on a per-packet 4K basis is prohibitive. With DMA_PMD pools, a 2MB page is allocated once from the buddy allocator, handed out in sub-blocks, and only returned when completely idle. Add two module parameters (dma_pmd.decrypt and dma_pmd.pin, with dma_pmd.decrypt auto-enabled when CC_ATTR_GUEST_MEM_ENCRYPT is active) and per-PMD-page state flags in meta->flags (DMA_PMD_DECRYPTED, DMA_PMD_PINNED): - On 2MB page allocation (dma_pmd_add_page), call dma_pmd_page_prepare() before splitting the compound page to invoke set_memory_decrypted() and/or the host pin hook. Skip conversion if the caller cannot sleep (!gfpflags_allow_blocking), since set_memory_decrypted() acquires cpa_lock and allocates PTE pages. - On 2MB page release (dma_pmd_release_page / dma_pmd_release_page_rcu), call dma_pmd_page_unprepare() before RCU free to restore set_memory_encrypted() and/or unpin before returning the 2MB page to the buddy allocator. If restoration fails, leak the 2MB page rather than returning a page with inconsistent encryption/pin state to buddy. - In dma_pmd_shrink_scan(), defer decrypted/pinned pages to the async reclaim workqueue (dma_pmd_free_list) instead of calling dma_pmd_release_page() inline under fs_reclaim. - Add dma_is_pmd_direct(phys) and use it in dma_direct_map_phys() to bypass swiotlb_map() bounce buffering for decrypted/pinned DMA_PMD pages, using phys_to_dma_direct() so force_dma_unencrypted() devices receive unencrypted DMA addresses. Signed-off-by: Luigi Rizzo --- drivers/iommu/dma-pmd-kunit.c | 2 +- drivers/iommu/dma-pmd-meta.c | 15 +++- drivers/iommu/dma-pmd-pool.c | 147 ++++++++++++++++++++++++++++------ drivers/iommu/dma-pmd-priv.h | 14 +++- include/linux/dma-pmd.h | 15 ++++ kernel/dma/direct.c | 6 +- 6 files changed, 168 insertions(+), 31 deletions(-) diff --git a/drivers/iommu/dma-pmd-kunit.c b/drivers/iommu/dma-pmd-kunit.c index c2363277e2ecd..7fcc2bcb315bc 100644 --- a/drivers/iommu/dma-pmd-kunit.c +++ b/drivers/iommu/dma-pmd-kunit.c @@ -53,7 +53,7 @@ static void test_meta_invalid_phys(struct kunit *test) static void dma_pmd_meta_set_pooled(struct dma_pmd_meta *m, bool pooled) { - WRITE_ONCE(m->pooled, pooled); + WRITE_ONCE(m->flags, pooled ? DMA_PMD_POOLED : 0); } static void test_meta_pooled_toggle(struct kunit *test) diff --git a/drivers/iommu/dma-pmd-meta.c b/drivers/iommu/dma-pmd-meta.c index 8f2bc7d77e5bd..744964d2c7974 100644 --- a/drivers/iommu/dma-pmd-meta.c +++ b/drivers/iommu/dma-pmd-meta.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -64,10 +65,22 @@ static __always_inline struct dma_pmd_meta *__dma_pmd_meta_of_pfn(unsigned long bool __dma_is_pmd_page(unsigned long pfn) { - return READ_ONCE(__dma_pmd_meta_of_pfn(pfn)->pooled); + return READ_ONCE(__dma_pmd_meta_of_pfn(pfn)->flags) & DMA_PMD_POOLED; } EXPORT_SYMBOL(__dma_is_pmd_page); +bool __dma_is_pmd_direct(unsigned long pfn) +{ + u8 flags = READ_ONCE(__dma_pmd_meta_of_pfn(pfn)->flags); + + if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) && + !(flags & DMA_PMD_DECRYPTED)) + return false; + return (flags & DMA_PMD_POOLED) && + (flags & (DMA_PMD_DECRYPTED | DMA_PMD_PINNED)); +} +EXPORT_SYMBOL(__dma_is_pmd_direct); + /** * dma_pmd_meta_of_pfn - Metadata for a PFN known to be used by DMA_PMD. * @pfn: PFN the caller already holds a struct page for diff --git a/drivers/iommu/dma-pmd-pool.c b/drivers/iommu/dma-pmd-pool.c index 1d4244ba422a3..deacb6f7d3610 100644 --- a/drivers/iommu/dma-pmd-pool.c +++ b/drivers/iommu/dma-pmd-pool.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include @@ -22,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -39,6 +41,14 @@ static LLIST_HEAD(dma_pmd_free_list); /* Dedicated WQ_MEM_RECLAIM workqueue, can run without allocations. */ static struct workqueue_struct *dma_pmd_wq __ro_after_init; +/* Mark pooled PMD pages decrypted for DMA (auto-enabled on CoCo guests). */ +static bool dma_pmd_decrypt __read_mostly; +module_param_named(decrypt, dma_pmd_decrypt, bool, 0644); + +/* Pin pooled PMD pages in the host hypervisor on allocation and unpin on release. */ +static bool dma_pmd_pin __read_mostly; +module_param_named(pin, dma_pmd_pin, bool, 0644); + /* * Running total and global ceiling on DMA_PMD pages pinned across all pools. * If zero, it is set at boot at 1/8 of total RAM. @@ -65,6 +75,70 @@ static void dma_pmd_pool_free_kref(struct kref *kref) dma_pmd_schedule_reclaim(); } +static int dma_pmd_page_prepare(struct page *page, struct dma_pmd_meta *meta, + bool can_block) +{ + bool want_decrypt = READ_ONCE(dma_pmd_decrypt); + bool want_pin = READ_ONCE(dma_pmd_pin); + void *vaddr = page_address(page); + int ret; + + if (!want_decrypt && !want_pin) + return 0; + + /* + * Decryption and host-pinning hypercalls may sleep. In atomic context, + * leave DMA_PMD_DECRYPTED/PINNED unset so the page is still pooled but + * uses normal swiotlb bounce buffering when required. + */ + if (!can_block) { + pr_warn_ratelimited("%s: cannot block but want %s %s\n", __func__, + want_decrypt ? "decrypt" : "", want_pin ? "pin" : ""); + return 0; + } + + /* + * Explicit page decryption is for CoCo guests (where force_dma_unencrypted() + * is true), not bare-metal SME hosts where 64-bit devices and the IOMMU + * set the encryption bit in DMA addresses and IOMMU PTEs. + */ + if (want_decrypt && !WARN_ON_ONCE(cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))) { + ret = set_memory_decrypted((unsigned long)vaddr, 1 << PMD_ORDER); + if (ret) + return ret; + /* Initialize cleartext cachelines after flipping encryption state. */ + memset(vaddr, 0, PMD_SIZE); + meta->flags |= DMA_PMD_DECRYPTED; + } + + if (want_pin) { + /* Hook point for hypervisor GPA range pinning. */ + meta->flags |= DMA_PMD_PINNED; + } + + return 0; +} + +static int dma_pmd_page_unprepare(struct dma_pmd_meta *meta) +{ + struct page *page = pfn_to_page(dma_pmd_meta_to_pfn(meta)); + + if (meta->flags & DMA_PMD_PINNED) { + /* Hook point for hypervisor GPA range unpinning. */ + WRITE_ONCE(meta->flags, meta->flags & ~DMA_PMD_PINNED); + } + + if (meta->flags & DMA_PMD_DECRYPTED) { + if (set_memory_encrypted((unsigned long)page_address(page), + 1 << PMD_ORDER)) { + pr_warn_ratelimited("dma_pmd: leaking PMD page that could not be re-encrypted\n"); + return -EIO; + } + WRITE_ONCE(meta->flags, meta->flags & ~DMA_PMD_DECRYPTED); + } + return 0; +} + /* * Releasing an idle PMD page proceeds in three stages: * @@ -74,7 +148,7 @@ static void dma_pmd_pool_free_kref(struct kref *kref) * pushed locklessly onto dma_pmd_free_list and dma_pmd_reclaim_work is * scheduled on dma_pmd_wq. * 2. In process context, dma_pmd_release_page() unmaps all IOMMU domains - * (dma_pmd_unmap_all()), clears meta->pooled so new lockless readers stop + * (dma_pmd_unmap_all()), clears DMA_PMD_POOLED so new lockless readers stop * entering @meta, and queues dma_pmd_release_page_rcu() via call_rcu(). * 3. After an RCU grace period (once no concurrent dma_pmd_free_page() reader * can still be dereferencing @meta), dma_pmd_release_page_rcu() unfreezes @@ -97,22 +171,21 @@ static void dma_pmd_release_page_rcu(struct rcu_head *head) * block is freed, the PMD frame can be reallocated and @meta overwritten. */ struct dma_pmd_meta *meta = container_of(head, struct dma_pmd_meta, rcu); - struct page *page = pfn_to_page(dma_pmd_meta_to_pfn(meta)); + struct page *block, *page = pfn_to_page(dma_pmd_meta_to_pfn(meta)); struct dma_pmd_pool *pool = READ_ONCE(meta->pool); - unsigned int nr = DMA_PMD_BLOCKS(pool->order); - unsigned int order = pool->order; + unsigned int order = pool->order, i, nr = DMA_PMD_BLOCKS(order); + bool leak = READ_ONCE(meta->flags) & DMA_PMD_DECRYPTED; unsigned long flags; - unsigned int i; - - for (i = 0; i < nr; i++) { - struct page *block = page + (i << order); - page_ref_unfreeze(block, 1); - __free_pages(block, order); + if (!leak) { + for (i = 0; i < nr; i++) { + block = page + (i << order); + page_ref_unfreeze(block, 1); + __free_pages(block, order); + } + atomic_long_dec(&dma_pmd_nr_pages); } - atomic_long_dec(&dma_pmd_nr_pages); - spin_lock_irqsave(&pool->lock, flags); pool->pmd_free_cnt++; spin_unlock_irqrestore(&pool->lock, flags); @@ -138,7 +211,9 @@ static void dma_pmd_release_page(struct dma_pmd_meta *meta) * dma_is_pmd_page() just before this may still be reading @meta, so * the PMD page and its metadata entry must outlive the grace period. */ - WRITE_ONCE(meta->pooled, false); + WRITE_ONCE(meta->flags, meta->flags & ~DMA_PMD_POOLED); + dma_pmd_page_unprepare(meta); + call_rcu(&meta->rcu, dma_pmd_release_page_rcu); } @@ -392,20 +467,33 @@ static struct dma_pmd_meta *dma_pmd_add_page(struct dma_pmd_pool *pool, return NULL; } - /* Fails with -EBUSY if a concurrent PFN walker holds a speculative ref. */ - if (split_page_compound(page, PMD_ORDER, pool->order)) { + meta = dma_pmd_meta_of_pfn(page_to_pfn(page)); + memset(meta, 0, sizeof(*meta)); + meta->pool = pool; + spin_lock_init(&meta->map_lock); + + if (dma_pmd_page_prepare(page, meta, can_block)) { __free_pages(page, PMD_ORDER); atomic_long_dec(&dma_pmd_nr_pages); return NULL; } - meta = dma_pmd_meta_of_pfn(page_to_pfn(page)); - memset(meta, 0, sizeof(*meta)); - meta->pool = pool; - spin_lock_init(&meta->map_lock); + /* Fails with -EBUSY if a concurrent PFN walker holds a speculative ref. */ + if (split_page_compound(page, PMD_ORDER, pool->order)) { + if (!dma_pmd_page_unprepare(meta)) { + __free_pages(page, PMD_ORDER); + atomic_long_dec(&dma_pmd_nr_pages); + } + return NULL; + } - bitmap_set(meta->dirty_bitmap, 0, nr); - meta->nr_dirty = nr; + if (meta->flags & DMA_PMD_DECRYPTED) { + bitmap_set(meta->free_bitmap, 0, nr); + meta->nr_free = nr; + } else { + bitmap_set(meta->dirty_bitmap, 0, nr); + meta->nr_dirty = nr; + } kref_get(&pool->refcount); @@ -418,7 +506,7 @@ static struct dma_pmd_meta *dma_pmd_add_page(struct dma_pmd_pool *pool, * function returns and the caller publishes the PMD page under * @pool->lock, whose release orders both stores against every consumer. */ - WRITE_ONCE(meta->pooled, true); + WRITE_ONCE(meta->flags, meta->flags | DMA_PMD_POOLED); return meta; } @@ -764,10 +852,18 @@ static unsigned long dma_pmd_shrink_scan(struct shrinker *shrink, /* * Retiring is done outside both locks: dma_pmd_release_page() unmaps * from the IOMMU, which is far too long to hold pool->lock for. + * Pages that need set_memory_encrypted() cannot be released under + * fs_reclaim (CPA allocates PTE pages on x86); hand them to the + * reclaim workqueue instead. */ list_for_each_entry_safe(meta, tmp, &release_list, list) { - list_del(&meta->list); - dma_pmd_release_page(meta); + list_del_init(&meta->list); + if (meta->flags & (DMA_PMD_DECRYPTED | DMA_PMD_PINNED)) { + llist_add(&meta->llnode, &dma_pmd_free_list); + dma_pmd_schedule_reclaim(); + } else { + dma_pmd_release_page(meta); + } } srcu_read_unlock(&dma_pmd_srcu, srcu_idx); @@ -806,6 +902,9 @@ static int __init dma_pmd_init(void) if (!dma_pmd_max_pages) dma_pmd_max_pages = max(totalram_pages() >> (PMD_ORDER + 3), 16UL); + if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) + dma_pmd_decrypt = true; + /* * Reclaim frees memory, so it must not queue behind arbitrary work on * system_wq when the machine is already short of it. Failure is not diff --git a/drivers/iommu/dma-pmd-priv.h b/drivers/iommu/dma-pmd-priv.h index b411ecb1fdafc..8c7a50d5b7220 100644 --- a/drivers/iommu/dma-pmd-priv.h +++ b/drivers/iommu/dma-pmd-priv.h @@ -107,10 +107,16 @@ enum { #define DMA_PMD_META_SHIFT 8 #define DMA_PMD_META_SIZE BIT(DMA_PMD_META_SHIFT) +enum { + DMA_PMD_POOLED = BIT(0), + DMA_PMD_DECRYPTED = BIT(1), + DMA_PMD_PINNED = BIT(2), +}; + /** * struct dma_pmd_meta - Metadata for a single DMA_PMD page - * @pooled: True while this page is owned by an dma_pmd_pool (offset 0) - * read locklessly by dma_is_pmd_page(). + * @flags: Bitmask of DMA_PMD_POOLED, DMA_PMD_DECRYPTED, DMA_PMD_PINNED + * (offset 0), read locklessly by dma_is_pmd_page() and dma_is_pmd_direct(). * @nr_free: Number of zeroed available blocks in @free_bitmap * @nr_dirty: Number of dirty available blocks in @dirty_bitmap * @map_lock: Spinlock protecting slow-path updates to @domains_mapped @@ -138,7 +144,7 @@ enum { * physical pages (128 KB per GB of RAM). */ struct dma_pmd_meta { - bool pooled; + u8 flags; u16 nr_free; u16 nr_dirty; spinlock_t map_lock; @@ -160,7 +166,7 @@ struct dma_pmd_meta { DECLARE_BITMAP(dirty_bitmap, 1U << PMD_ORDER) ____cacheline_aligned; } __aligned(DMA_PMD_META_SIZE); -static_assert(offsetof(struct dma_pmd_meta, pooled) == 0); +static_assert(offsetof(struct dma_pmd_meta, flags) == 0); static_assert(sizeof(struct dma_pmd_meta) == DMA_PMD_META_SIZE); static inline unsigned int dma_pmd_meta_avail(const struct dma_pmd_meta *m) diff --git a/include/linux/dma-pmd.h b/include/linux/dma-pmd.h index 7b7e9477d44e1..c9775e86979f9 100644 --- a/include/linux/dma-pmd.h +++ b/include/linux/dma-pmd.h @@ -16,6 +16,7 @@ struct dma_pmd_pool; extern void *dma_pmd_meta_array; bool __dma_is_pmd_page(unsigned long pfn); +bool __dma_is_pmd_direct(unsigned long pfn); static inline bool dma_is_pmd_page(unsigned long pfn) { @@ -29,6 +30,15 @@ static inline bool dma_is_pmd_page(unsigned long pfn) return __dma_is_pmd_page(pfn); } +static inline bool dma_is_pmd_direct(phys_addr_t phys) +{ + /* Pairs with smp_store_release() in dma_pmd_meta_init(). */ + if (likely(!smp_load_acquire(&dma_pmd_meta_array))) + return false; + + return __dma_is_pmd_direct(phys >> PAGE_SHIFT); +} + bool __dma_pmd_free_page(struct page *page); static inline bool dma_pmd_free_page(struct page *page) @@ -117,6 +127,11 @@ static inline bool dma_is_pmd_page(unsigned long pfn) return false; } +static inline bool dma_is_pmd_direct(phys_addr_t phys) +{ + return false; +} + static inline bool dma_pmd_free_page(struct page *page) { return false; diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index da665ca22d5c0..a786c2869b869 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -7,6 +7,7 @@ #include /* for max_pfn */ #include #include +#include #include #include #include @@ -679,7 +680,10 @@ dma_addr_t dma_direct_map_phys(struct device *dev, phys_addr_t phys, attrs |= DMA_ATTR_CC_SHARED; } - if (is_swiotlb_force_bounce(dev)) { + if (dma_is_pmd_direct(phys)) { + if (force_dma_unencrypted(dev)) + attrs |= DMA_ATTR_CC_SHARED; + } else if (is_swiotlb_force_bounce(dev)) { if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT)) return DMA_MAPPING_ERROR; -- 2.56.0.rc1.315.gc6ed9934b7-goog