From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7E3EC17BB21 for ; Mon, 28 Jul 2025 07:08:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753686528; cv=none; b=Mahiq9L7sALWSneVfXQiKaEZ44Iys/1SSDNzrvRuExiftXBawV3+wQydTzpmq1H/Mz6gZlWGkd8TroKqpUz6/xwmOOqW6FuujB10FVH/WZ8SoyWDvD8kCBETTZrmMRIWhJtywxK+mFFLOK7VE6QPswBiFDhzCjd0bmJhMtR6/cM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753686528; c=relaxed/simple; bh=aXNZbva1Tx5Hx67tbz/PrNLQRNAdOtft3A71HfAyhJk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=p9PgwBmYJAp9nQSf49RNIfdsk2TAn5W3G0CFuCCyB2ltpmyUXnpU23zmPkOFLdX1MKzCIx89msD+5ueZYPr2gyNfOyG7s3zvJtQMpqym7qSapohB+wg6pfZ7tKRTTRCYivneO2PS6G4I2H8w1zrCQk5HnQPzCVs+tuYYgEgSrxA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JYkOGxUm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JYkOGxUm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3004BC4CEE7; Mon, 28 Jul 2025 07:08:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753686528; bh=aXNZbva1Tx5Hx67tbz/PrNLQRNAdOtft3A71HfAyhJk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JYkOGxUmi5fx4tHY77ePDxlF8S82+8RR5A7xrkKa48Lk/dfFTuIWVOVAlx0IvsUfW lGWQdvuFcdycKII/TgT87P+6XSq8ZZA8lApidy9sO8ufY68LeXCaEdlCAi9drnI5iT kMkdvjPvnvKg60EZOrBgv8FHBrr9KGVqp+zEW4VtW2y/qfloDA35eyKQ+nL2VizXyj 3jlIH+7kIcKvYsQETkb5dhFA05bhFy8SoSR9GXOzQC4vZ9X6E0GoU8aug16fXf+hDQ tTSdbSYSQKBPUc40b5dwM8U8Q0LSd3zw49Bn4jsS024hPMk8HSHHS+qNgPNiSWvr5U LA1fFfBwyIWCg== Date: Mon, 28 Jul 2025 10:08:41 +0300 From: Leon Romanovsky To: Boshi Yu Cc: jgg@ziepe.ca, linux-rdma@vger.kernel.org, chengyou@linux.alibaba.com, kaishen@linux.alibaba.com Subject: Re: [PATCH for-next 1/3] RDMA/erdma: Use dma_map_page to map scatter MTT buffer Message-ID: <20250728070841.GB402218@unreal> References: <20250725055410.67520-1-boshiyu@linux.alibaba.com> <20250725055410.67520-2-boshiyu@linux.alibaba.com> <20250727112757.GZ402218@unreal> <5cd4c86c-fc28-4ff5-a135-4d468bff7f36@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5cd4c86c-fc28-4ff5-a135-4d468bff7f36@linux.alibaba.com> On Mon, Jul 28, 2025 at 11:08:46AM +0800, Boshi Yu wrote: > > > On 2025/7/27 19:27, Leon Romanovsky wrote: > > On Fri, Jul 25, 2025 at 01:53:54PM +0800, Boshi Yu wrote: > > > Each high-level indirect MTT entry is assumed to point to exactly one page > > > of the low-level MTT buffer, but dma_map_sg may merge contiguous physical > > > pages when mapping. To avoid extra overhead from splitting merged regions, > > > use dma_map_page to map the scatter MTT buffer page by page. > > > > > > Reviewed-by: Cheng Xu > > > Signed-off-by: Boshi Yu > > > --- > > > drivers/infiniband/hw/erdma/erdma_verbs.c | 110 ++++++++++++++-------- > > > drivers/infiniband/hw/erdma/erdma_verbs.h | 4 +- > > > 2 files changed, 71 insertions(+), 43 deletions(-) > > > > <...> > > > > > + pg_dma = vzalloc(npages * sizeof(dma_addr_t)); > > > + if (!pg_dma) > > > + return 0; > > > - sg_init_table(sglist, npages); > > > + addr = buf; > > > for (i = 0; i < npages; i++) { > > > - pg = vmalloc_to_page(buf); > > > + pg = vmalloc_to_page(addr); > > > > <...> > > > + > > > + pg_dma[i] = dma_map_page(&dev->pdev->dev, pg, 0, PAGE_SIZE, > > > + DMA_TO_DEVICE); > > > > Does it work? > > Hi Leon, > > I would like to confirm which part you think is not working properly. I > guess that you might be concerned that if the buffer is not page-aligned, it > could cause problems with dma_map_page. > > In fact, when allocating the MTT buffer, we ensure that it is always > page-aligned and that its length is a multiple of PAGE_SIZE. We have also > tested the new code in our production environment, and it works well. > > Look forward to your further reply if I have misunderstood your concerns. DMA API expects Kmalloc addresses and not Vmalloc ones. Thanks