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[34.83.46.153]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-365b4c196ecsm3120637a91.6.2026.05.06.11.16.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 May 2026 11:16:30 -0700 (PDT) Date: Wed, 6 May 2026 18:16:27 +0000 From: Samiullah Khawaja To: Leon Romanovsky Cc: Marek Szyprowski , Robin Murphy , Jon Mason , Dave Jiang , Allen Hubbe , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, ntb@lists.linux.dev Subject: Re: [PATCH v2 6/6] dma-debug: Ensure mappings are created and released with matching attributes Message-ID: References: <20260501-dma-attrs-debug-v2-0-8dbac75cd501@nvidia.com> <20260501-dma-attrs-debug-v2-6-8dbac75cd501@nvidia.com> Precedence: bulk X-Mailing-List: ntb@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20260501-dma-attrs-debug-v2-6-8dbac75cd501@nvidia.com> On Fri, May 01, 2026 at 09:35:10AM +0300, Leon Romanovsky wrote: >From: Leon Romanovsky > >The DMA API expects that callers use the same attributes when mapping >and unmapping. Add tracking to verify this and catch mismatches. > >Signed-off-by: Leon Romanovsky >--- > kernel/dma/debug.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > >diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c >index 3dfed51c3d9aa..c38efc1ac8d6c 100644 >--- a/kernel/dma/debug.c >+++ b/kernel/dma/debug.c >@@ -1074,6 +1074,29 @@ static void check_unmap(struct dma_debug_entry *ref) > type2name[entry->type]); > } > >+ /* >+ * This may be no bug in reality - but DMA API still expects >+ * that entry is unmapped with same attributes as it was mapped. >+ * >+ * DMA_ATTR_UNMAP_VALID lists the attributes that must be identical >+ * between map and unmap. Any attribute outside this set (e.g. >+ * DMA_ATTR_NO_WARN, DMA_ATTR_SKIP_CPU_SYNC) is allowed to differ. >+ */ >+#define DMA_ATTR_UNMAP_VALID \ >+ (DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_FORCE_CONTIGUOUS | \ >+ DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT | DMA_ATTR_PRIVILEGED | \ >+ DMA_ATTR_CC_SHARED) >+ if ((ref->attrs & DMA_ATTR_UNMAP_VALID) != >+ (entry->attrs & DMA_ATTR_UNMAP_VALID)) { >+ err_printk(ref->dev, entry, >+ "device driver frees " >+ "DMA memory with different attributes " >+ "[device address=0x%016llx] [size=%llu bytes] " >+ "[mapped with 0x%lx] [unmapped with 0x%lx]\n", >+ ref->dev_addr, ref->size, entry->attrs, ref->attrs); >+ } >+#undef DMA_ATTR_UNMAP_VALID >+ > hash_bucket_del(entry); > put_hash_bucket(bucket, flags); > > >-- >2.53.0 > > Reviewed-by: Samiullah Khawaja