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[35.189.192.250]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-496c45e0424sm84654015e9.13.2026.07.28.07.25.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 07:25:19 -0700 (PDT) Date: Tue, 28 Jul 2026 14:25:11 +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, Jason Gunthorpe , Michael Kelley Subject: Re: [PATCH v8 05/23] swiotlb: Preserve allocation virtual address for dynamic pools Message-ID: References: <20260717180442.110954-1-aneesh.kumar@kernel.org> <20260717180442.110954-6-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260717180442.110954-6-aneesh.kumar@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260728_072522_739880_C471194D X-CRM114-Status: GOOD ( 27.76 ) 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 Fri, Jul 17, 2026 at 11:34:23PM +0530, Aneesh Kumar K.V (Arm) wrote: > swiotlb_alloc_tlb() can allocate from the DMA atomic pool when a decrypted > pool is needed from atomic context. With CONFIG_DMA_DIRECT_REMAP, the > atomic pool is backed by remapped virtual addresses, which are not the same > as the direct-map addresses returned by phys_to_virt(). > > swiotlb_init_io_tlb_pool() currently reconstructs the pool virtual address > from the physical start address. For atomic-pool backed allocations this > stores the wrong address in pool->vaddr. Later, swiotlb_free_tlb() passes > that address to dma_free_from_pool(), which will fail to recognize the > chunk > > Pass the virtual address returned by the allocation path into > swiotlb_init_io_tlb_pool(), and store that address in pool->vaddr. This > keeps the pool free path using the same virtual address as the allocator. > > Fixes: 79636caad361 ("swiotlb: if swiotlb is full, fall back to a transient memory pool") > Reviewed-by: Jason Gunthorpe > Tested-by: Michael Kelley > Tested-by: Mostafa Saleh > Reviewed-by: Petr Tesarik > Signed-off-by: Aneesh Kumar K.V (Arm) Reviewed-by: Mostafa Saleh Thanks, Mostafa > --- > kernel/dma/swiotlb.c | 31 +++++++++++++++++++------------ > 1 file changed, 19 insertions(+), 12 deletions(-) > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 1abd3e6146f4..6e8db52866bf 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -266,9 +266,9 @@ void __init swiotlb_update_mem_attributes(void) > } > > static void swiotlb_init_io_tlb_pool(struct io_tlb_pool *mem, phys_addr_t start, > - unsigned long nslabs, bool late_alloc, unsigned int nareas) > + void *vaddr, unsigned long nslabs, bool late_alloc, > + unsigned int nareas) > { > - void *vaddr = phys_to_virt(start); > unsigned long bytes = nslabs << IO_TLB_SHIFT, i; > > mem->nslabs = nslabs; > @@ -409,7 +409,7 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags, > return; > } > > - swiotlb_init_io_tlb_pool(mem, __pa(tlb), nslabs, false, nareas); > + swiotlb_init_io_tlb_pool(mem, __pa(tlb), tlb, nslabs, false, nareas); > add_mem_pool(&io_tlb_default_mem, mem); > > if (flags & SWIOTLB_VERBOSE) > @@ -507,7 +507,7 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask, > > set_memory_decrypted((unsigned long)vstart, > (nslabs << IO_TLB_SHIFT) >> PAGE_SHIFT); > - swiotlb_init_io_tlb_pool(mem, virt_to_phys(vstart), nslabs, true, > + swiotlb_init_io_tlb_pool(mem, virt_to_phys(vstart), vstart, nslabs, true, > nareas); > add_mem_pool(&io_tlb_default_mem, mem); > > @@ -605,25 +605,26 @@ static struct page *alloc_dma_pages(gfp_t gfp, size_t bytes, u64 phys_limit) > * @bytes: Size of the buffer. > * @phys_limit: Maximum allowed physical address of the buffer. > * @gfp: GFP flags for the allocation. > + * @vaddr: Receives the virtual address for the allocated buffer. > * > * Return: Allocated pages, or %NULL on allocation failure. > */ > static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes, > - u64 phys_limit, gfp_t gfp) > + u64 phys_limit, gfp_t gfp, void **vaddr) > { > struct page *page; > > + *vaddr = NULL; > + > /* > * Allocate from the atomic pools if memory is encrypted and > * the allocation is atomic, because decrypting may block. > */ > if (!gfpflags_allow_blocking(gfp) && dev && force_dma_unencrypted(dev)) { > - void *vaddr; > - > if (!IS_ENABLED(CONFIG_DMA_COHERENT_POOL)) > return NULL; > > - return dma_alloc_from_pool(dev, bytes, &vaddr, gfp, > + return dma_alloc_from_pool(dev, bytes, vaddr, gfp, > dma_coherent_ok); > } > > @@ -645,6 +646,8 @@ static struct page *swiotlb_alloc_tlb(struct device *dev, size_t bytes, > return NULL; > } > > + if (page) > + *vaddr = phys_to_virt(page_to_phys(page)); > return page; > } > > @@ -685,6 +688,7 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev, > { > struct io_tlb_pool *pool; > unsigned int slot_order; > + void *tlb_vaddr; > struct page *tlb; > size_t pool_size; > size_t tlb_size; > @@ -701,7 +705,8 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev, > pool->areas = (void *)pool + sizeof(*pool); > > tlb_size = nslabs << IO_TLB_SHIFT; > - while (!(tlb = swiotlb_alloc_tlb(dev, tlb_size, phys_limit, gfp))) { > + while (!(tlb = swiotlb_alloc_tlb(dev, tlb_size, phys_limit, gfp, > + &tlb_vaddr))) { > if (nslabs <= minslabs) > goto error_tlb; > nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE); > @@ -715,11 +720,12 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev, > if (!pool->slots) > goto error_slots; > > - swiotlb_init_io_tlb_pool(pool, page_to_phys(tlb), nslabs, true, nareas); > + swiotlb_init_io_tlb_pool(pool, page_to_phys(tlb), tlb_vaddr, nslabs, > + true, nareas); > return pool; > > error_slots: > - swiotlb_free_tlb(page_address(tlb), tlb_size); > + swiotlb_free_tlb(tlb_vaddr, tlb_size); > error_tlb: > kfree(pool); > error: > @@ -1851,7 +1857,8 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem, > > set_memory_decrypted((unsigned long)phys_to_virt(rmem->base), > rmem->size >> PAGE_SHIFT); > - swiotlb_init_io_tlb_pool(pool, rmem->base, nslabs, > + swiotlb_init_io_tlb_pool(pool, rmem->base, phys_to_virt(rmem->base), > + nslabs, > false, nareas); > mem->force_bounce = true; > mem->for_alloc = true; > -- > 2.43.0 >