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[34.38.181.8]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-454913049ecsm39669111f8f.19.2026.05.13.07.00.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 07:00:53 -0700 (PDT) Date: Wed, 13 May 2026 14:00:47 +0000 From: Mostafa Saleh To: "Aneesh Kumar K.V (Arm)" Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org Subject: Re: [PATCH v4 03/13] dma-pool: track decrypted atomic pools and select them via attrs Message-ID: References: <20260512090408.794195-1-aneesh.kumar@kernel.org> <20260512090408.794195-4-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260512090408.794195-4-aneesh.kumar@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260513_070057_160046_E6234594 X-CRM114-Status: GOOD ( 32.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, May 12, 2026 at 02:33:58PM +0530, Aneesh Kumar K.V (Arm) wrote: > Teach the atomic DMA pool code to distinguish between encrypted and > decrypted pools, and make pool allocation select the matching pool based > on DMA attributes. > > Introduce a dma_gen_pool wrapper that records whether a pool is > decrypted, initialize that state when the atomic pools are created, and > use it when expanding and resizing the pools. Update dma_alloc_from_pool() > to take attrs and skip pools whose encrypted/decrypted state does not > match DMA_ATTR_CC_SHARED. Update dma_free_from_pool() accordingly. > > Also pass DMA_ATTR_CC_SHARED from the swiotlb atomic allocation path > so decrypted swiotlb allocations are taken from the correct atomic pool. > > Signed-off-by: Aneesh Kumar K.V (Arm) > --- > drivers/iommu/dma-iommu.c | 2 +- > include/linux/dma-map-ops.h | 2 +- > kernel/dma/direct.c | 11 ++- > kernel/dma/pool.c | 163 +++++++++++++++++++++++------------- > kernel/dma/swiotlb.c | 7 +- > 5 files changed, 122 insertions(+), 63 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 54d96e847f16..c2595bee3d41 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -1673,7 +1673,7 @@ void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, > if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && > !gfpflags_allow_blocking(gfp) && !coherent) > page = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &cpu_addr, > - gfp, NULL); > + gfp, attrs, NULL); > else > cpu_addr = iommu_dma_alloc_pages(dev, size, &page, gfp, attrs); > if (!cpu_addr) > diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h > index 6a1832a73cad..696b2c3a2305 100644 > --- a/include/linux/dma-map-ops.h > +++ b/include/linux/dma-map-ops.h > @@ -212,7 +212,7 @@ void *dma_common_pages_remap(struct page **pages, size_t size, pgprot_t prot, > void dma_common_free_remap(void *cpu_addr, size_t size); > > struct page *dma_alloc_from_pool(struct device *dev, size_t size, > - void **cpu_addr, gfp_t flags, > + void **cpu_addr, gfp_t flags, unsigned long attrs, > bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)); > bool dma_free_from_pool(struct device *dev, void *start, size_t size); > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 0c2e1f8436ce..dc2907439b3d 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -162,7 +162,7 @@ static bool dma_direct_use_pool(struct device *dev, gfp_t gfp) > } > > static void *dma_direct_alloc_from_pool(struct device *dev, size_t size, > - dma_addr_t *dma_handle, gfp_t gfp) > + dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) > { > struct page *page; > u64 phys_limit; > @@ -172,7 +172,8 @@ static void *dma_direct_alloc_from_pool(struct device *dev, size_t size, > return NULL; > > gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit); > - page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok); > + page = dma_alloc_from_pool(dev, size, &ret, gfp, attrs, > + dma_coherent_ok); > if (!page) > return NULL; > *dma_handle = phys_to_dma_direct(dev, page_to_phys(page)); > @@ -261,7 +262,8 @@ void *dma_direct_alloc(struct device *dev, size_t size, > */ > if ((remap || (attrs & DMA_ATTR_CC_SHARED)) && > dma_direct_use_pool(dev, gfp)) > - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > + return dma_direct_alloc_from_pool(dev, size, dma_handle, > + gfp, attrs); > > if (is_swiotlb_for_alloc(dev)) { > page = dma_direct_alloc_swiotlb(dev, size); > @@ -397,7 +399,8 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size, > attrs |= DMA_ATTR_CC_SHARED; > > if ((attrs & DMA_ATTR_CC_SHARED) && dma_direct_use_pool(dev, gfp)) > - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > + return dma_direct_alloc_from_pool(dev, size, dma_handle, > + gfp, attrs); > > if (is_swiotlb_for_alloc(dev)) { > page = dma_direct_alloc_swiotlb(dev, size); > diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c > index 2b2fbb709242..75f0eba48a23 100644 > --- a/kernel/dma/pool.c > +++ b/kernel/dma/pool.c > @@ -12,12 +12,18 @@ > #include > #include > #include > +#include > > -static struct gen_pool *atomic_pool_dma __ro_after_init; > +struct dma_gen_pool { > + bool unencrypted; > + struct gen_pool *pool; > +}; > + > +static struct dma_gen_pool atomic_pool_dma __ro_after_init; > static unsigned long pool_size_dma; > -static struct gen_pool *atomic_pool_dma32 __ro_after_init; > +static struct dma_gen_pool atomic_pool_dma32 __ro_after_init; > static unsigned long pool_size_dma32; > -static struct gen_pool *atomic_pool_kernel __ro_after_init; > +static struct dma_gen_pool atomic_pool_kernel __ro_after_init; > static unsigned long pool_size_kernel; > > /* Size can be defined by the coherent_pool command line */ > @@ -76,7 +82,7 @@ static bool cma_in_zone(gfp_t gfp) > return true; > } > > -static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size, > +static int atomic_pool_expand(struct dma_gen_pool *dma_pool, size_t pool_size, > gfp_t gfp) > { > unsigned int order; > @@ -113,12 +119,15 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size, > * Memory in the atomic DMA pools must be unencrypted, the pools do not > * shrink so no re-encryption occurs in dma_direct_free(). > */ > - ret = set_memory_decrypted((unsigned long)page_to_virt(page), > + if (dma_pool->unencrypted) { > + ret = set_memory_decrypted((unsigned long)page_to_virt(page), > 1 << order); > - if (ret) > - goto remove_mapping; > - ret = gen_pool_add_virt(pool, (unsigned long)addr, page_to_phys(page), > - pool_size, NUMA_NO_NODE); > + if (ret) > + goto remove_mapping; > + } > + > + ret = gen_pool_add_virt(dma_pool->pool, (unsigned long)addr, > + page_to_phys(page), pool_size, NUMA_NO_NODE); > if (ret) > goto encrypt_mapping; > > @@ -126,11 +135,15 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size, > return 0; > > encrypt_mapping: > - ret = set_memory_encrypted((unsigned long)page_to_virt(page), > - 1 << order); > - if (WARN_ON_ONCE(ret)) { > - /* Decrypt succeeded but encrypt failed, purposely leak */ > - goto out; > + if (dma_pool->unencrypted) { > + int rc; > + > + rc = set_memory_encrypted((unsigned long)page_to_virt(page), > + 1 << order); > + if (WARN_ON_ONCE(rc)) { > + /* Decrypt succeeded but encrypt failed, purposely leak */ > + goto out; > + } > } > remove_mapping: > #ifdef CONFIG_DMA_DIRECT_REMAP > @@ -142,46 +155,52 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size, > return ret; > } > > -static void atomic_pool_resize(struct gen_pool *pool, gfp_t gfp) > +static void atomic_pool_resize(struct dma_gen_pool *dma_pool, gfp_t gfp) > { > - if (pool && gen_pool_avail(pool) < atomic_pool_size) > - atomic_pool_expand(pool, gen_pool_size(pool), gfp); > + if (dma_pool->pool && gen_pool_avail(dma_pool->pool) < atomic_pool_size) > + atomic_pool_expand(dma_pool, gen_pool_size(dma_pool->pool), gfp); > } > > static void atomic_pool_work_fn(struct work_struct *work) > { > if (IS_ENABLED(CONFIG_ZONE_DMA)) > - atomic_pool_resize(atomic_pool_dma, > + atomic_pool_resize(&atomic_pool_dma, > GFP_KERNEL | GFP_DMA); > if (IS_ENABLED(CONFIG_ZONE_DMA32)) > - atomic_pool_resize(atomic_pool_dma32, > + atomic_pool_resize(&atomic_pool_dma32, > GFP_KERNEL | GFP_DMA32); > - atomic_pool_resize(atomic_pool_kernel, GFP_KERNEL); > + atomic_pool_resize(&atomic_pool_kernel, GFP_KERNEL); > } > > -static __init struct gen_pool *__dma_atomic_pool_init(size_t pool_size, > - gfp_t gfp) > +static __init struct dma_gen_pool *__dma_atomic_pool_init(struct dma_gen_pool *dma_pool, > + size_t pool_size, gfp_t gfp) > { > - struct gen_pool *pool; > int ret; > > - pool = gen_pool_create(PAGE_SHIFT, NUMA_NO_NODE); > - if (!pool) > + dma_pool->pool = gen_pool_create(PAGE_SHIFT, NUMA_NO_NODE); > + if (!dma_pool->pool) > return NULL; > > - gen_pool_set_algo(pool, gen_pool_first_fit_order_align, NULL); > + gen_pool_set_algo(dma_pool->pool, gen_pool_first_fit_order_align, NULL); > + > + /* if platform is using memory encryption atomic pools are by default decrypted. */ > + if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) > + dma_pool->unencrypted = true; > + else > + dma_pool->unencrypted = false; I believe that’s a good start, although we might need to have more fine grained policies in the future as CC guests might need encrypted pools Reviewed-by: Mostafa Saleh Thanks, Mostafa > > - ret = atomic_pool_expand(pool, pool_size, gfp); > + ret = atomic_pool_expand(dma_pool, pool_size, gfp); > if (ret) { > - gen_pool_destroy(pool); > + gen_pool_destroy(dma_pool->pool); > + dma_pool->pool = NULL; > pr_err("DMA: failed to allocate %zu KiB %pGg pool for atomic allocation\n", > pool_size >> 10, &gfp); > return NULL; > } > > pr_info("DMA: preallocated %zu KiB %pGg pool for atomic allocations\n", > - gen_pool_size(pool) >> 10, &gfp); > - return pool; > + gen_pool_size(dma_pool->pool) >> 10, &gfp); > + return dma_pool; > } > > #ifdef CONFIG_ZONE_DMA32 > @@ -207,21 +226,22 @@ static int __init dma_atomic_pool_init(void) > > /* All memory might be in the DMA zone(s) to begin with */ > if (has_managed_zone(ZONE_NORMAL)) { > - atomic_pool_kernel = __dma_atomic_pool_init(atomic_pool_size, > - GFP_KERNEL); > - if (!atomic_pool_kernel) > + __dma_atomic_pool_init(&atomic_pool_kernel, atomic_pool_size, GFP_KERNEL); > + if (!atomic_pool_kernel.pool) > ret = -ENOMEM; > } > + > if (has_managed_dma()) { > - atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size, > - GFP_KERNEL | GFP_DMA); > - if (!atomic_pool_dma) > + __dma_atomic_pool_init(&atomic_pool_dma, atomic_pool_size, > + GFP_KERNEL | GFP_DMA); > + if (!atomic_pool_dma.pool) > ret = -ENOMEM; > } > + > if (has_managed_dma32) { > - atomic_pool_dma32 = __dma_atomic_pool_init(atomic_pool_size, > - GFP_KERNEL | GFP_DMA32); > - if (!atomic_pool_dma32) > + __dma_atomic_pool_init(&atomic_pool_dma32, atomic_pool_size, > + GFP_KERNEL | GFP_DMA32); > + if (!atomic_pool_dma32.pool) > ret = -ENOMEM; > } > > @@ -230,19 +250,44 @@ static int __init dma_atomic_pool_init(void) > } > postcore_initcall(dma_atomic_pool_init); > > -static inline struct gen_pool *dma_guess_pool(struct gen_pool *prev, gfp_t gfp) > +static inline struct dma_gen_pool *__dma_guess_pool(struct dma_gen_pool *first, > + struct dma_gen_pool *second, struct dma_gen_pool *third) > +{ > + if (first->pool) > + return first; > + if (second && second->pool) > + return second; > + if (third && third->pool) > + return third; > + return NULL; > +} > + > +static inline struct dma_gen_pool *dma_guess_pool(struct dma_gen_pool *prev, > + gfp_t gfp) > { > - if (prev == NULL) { > + if (!prev) { > if (gfp & GFP_DMA) > - return atomic_pool_dma ?: atomic_pool_dma32 ?: atomic_pool_kernel; > + return __dma_guess_pool(&atomic_pool_dma, > + &atomic_pool_dma32, > + &atomic_pool_kernel); > + > if (gfp & GFP_DMA32) > - return atomic_pool_dma32 ?: atomic_pool_dma ?: atomic_pool_kernel; > - return atomic_pool_kernel ?: atomic_pool_dma32 ?: atomic_pool_dma; > + return __dma_guess_pool(&atomic_pool_dma32, > + &atomic_pool_dma, > + &atomic_pool_kernel); > + > + return __dma_guess_pool(&atomic_pool_kernel, > + &atomic_pool_dma32, > + &atomic_pool_dma); > } > - if (prev == atomic_pool_kernel) > - return atomic_pool_dma32 ? atomic_pool_dma32 : atomic_pool_dma; > - if (prev == atomic_pool_dma32) > - return atomic_pool_dma; > + > + if (prev == &atomic_pool_kernel) > + return __dma_guess_pool(&atomic_pool_dma32, > + &atomic_pool_dma, NULL); > + > + if (prev == &atomic_pool_dma32) > + return __dma_guess_pool(&atomic_pool_dma, NULL, NULL); > + > return NULL; > } > > @@ -272,16 +317,20 @@ static struct page *__dma_alloc_from_pool(struct device *dev, size_t size, > } > > struct page *dma_alloc_from_pool(struct device *dev, size_t size, > - void **cpu_addr, gfp_t gfp, > + void **cpu_addr, gfp_t gfp, unsigned long attrs, > bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)) > { > - struct gen_pool *pool = NULL; > + struct dma_gen_pool *dma_pool = NULL; > struct page *page; > bool pool_found = false; > > - while ((pool = dma_guess_pool(pool, gfp))) { > + while ((dma_pool = dma_guess_pool(dma_pool, gfp))) { > + > + if (dma_pool->unencrypted != !!(attrs & DMA_ATTR_CC_SHARED)) > + continue; > + nit: If we fail to find a matching pool, a slightly misleading message is printed as pool_found = false > pool_found = true; > - page = __dma_alloc_from_pool(dev, size, pool, cpu_addr, > + page = __dma_alloc_from_pool(dev, size, dma_pool->pool, cpu_addr, > phys_addr_ok); > if (page) > return page; > @@ -296,12 +345,14 @@ struct page *dma_alloc_from_pool(struct device *dev, size_t size, > > bool dma_free_from_pool(struct device *dev, void *start, size_t size) > { > - struct gen_pool *pool = NULL; > + struct dma_gen_pool *dma_pool = NULL; > + > + while ((dma_pool = dma_guess_pool(dma_pool, 0))) { > > - while ((pool = dma_guess_pool(pool, 0))) { > - if (!gen_pool_has_addr(pool, (unsigned long)start, size)) > + if (!gen_pool_has_addr(dma_pool->pool, (unsigned long)start, size)) > continue; > - gen_pool_free(pool, (unsigned long)start, size); > + > + gen_pool_free(dma_pool->pool, (unsigned long)start, size); > return true; > } > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 1abd3e6146f4..ab4eccbaa076 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -612,6 +612,7 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes, > u64 phys_limit, gfp_t gfp) > { > struct page *page; > + unsigned long attrs = 0; > > /* > * Allocate from the atomic pools if memory is encrypted and > @@ -623,8 +624,12 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes, > if (!IS_ENABLED(CONFIG_DMA_COHERENT_POOL)) > return NULL; > > + /* swiotlb considered decrypted by default */ > + if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) > + attrs = DMA_ATTR_CC_SHARED; > + > return dma_alloc_from_pool(dev, bytes, &vaddr, gfp, > - dma_coherent_ok); > + attrs, dma_coherent_ok); > } > > gfp &= ~GFP_ZONEMASK; > -- > 2.43.0 >