From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 63D2E39EF16; Tue, 21 Jul 2026 14:29:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784644169; cv=none; b=TFb3PdFFfKNRB2tbP1ZLymyatrt5wd2q9YZtBo/MsYeGmW2Q24uZr/bSRWnURvKB3DCYdF7EZJ/48labjIsulTkq1t+rIzxXosB6yOuhfRDJvZmNxR+snd6di5Ypo4cgp85Gr479z+n3KQIm/ZycIrQOU5dDfFYbCTqx5YpbQuM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784644169; c=relaxed/simple; bh=QH4RFAHkBOrpSezy4lFQGFmp/CUrmtoTSqvH8wmrqe4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ex7h5g8wZunCZ2ssFTK+PIGrqtKFLS/2xw+dv2kuH+gGxhTxmPHD27dfRkaokA4NV/kRHNm9PzG5HvU5nxgcFCNxyWL++o919nDPXxl3SLWyB2T2kg52qPji+6HfchZ2VI3C4w1+V1/Sx1oUp02AGa4pQjrl/FH+lU4br3VdQ40= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z6Y53Eln; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z6Y53Eln" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7F491F000E9; Tue, 21 Jul 2026 14:29:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784644168; bh=1soRxN4hiDcUXCxjs1PA7SeZGbKgmvbO8BnI4N1ZFe8=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Z6Y53ElnThJz/QmjNlBI90Yu7tbBuCvQU60QJ4DbRT5TXWdL7w3KuZzUdsCjKtoL/ 71ZaLms1OHJ+aJGCsLyIDPyM7gGELMJkUoUEEKbfKXlEoG+CcCrbpbAg43lxbizIqO yXWwFnJWX4Ru3nShSGjh7T+m6/UYy1o50khWKiQF8rvhylkfkDK/1Kki7v+jYxq5aI gO/tbH5nUZoF4TeZXpFnsJTsnW6/YStJLzyv9G5e7g6RhjKNbNUznJMyPNGHNkYE0+ ZTUeuFNaF4ExWmaFhhdtjEOn8TaeQv52hbnyhHF4K8laJqqVGxQz+/SpgRyB1FtKpa iraCr9pMDtqtA== Date: Tue, 21 Jul 2026 17:29:21 +0300 From: Leon Romanovsky To: "Aneesh Kumar K.V" 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 , Mostafa Saleh , 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, stable@vger.kernel.org, Michael Kelley , Jason Gunthorpe Subject: Re: [PATCH v8 01/23] dma-direct: return struct page from dma_direct_alloc_from_pool() Message-ID: <20260721142921.GN110966@unreal> References: <20260717180442.110954-1-aneesh.kumar@kernel.org> <20260717180442.110954-2-aneesh.kumar@kernel.org> <20260721115456.GI110966@unreal> Precedence: bulk X-Mailing-List: linux-s390@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: On Tue, Jul 21, 2026 at 07:50:10PM +0530, Aneesh Kumar K.V wrote: > Leon Romanovsky writes: > > > On Fri, Jul 17, 2026 at 11:34:19PM +0530, Aneesh Kumar K.V (Arm) wrote: > >> Commit 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool > >> helper") changed dma_direct_alloc_from_pool() to return the CPU address > >> from dma_alloc_from_pool(). That fits dma_direct_alloc(), but > >> dma_direct_alloc_pages() also uses the helper and expects a struct page *. > >> > >> Fix this by making dma_direct_alloc_from_pool() return the struct page * > >> again, and pass the CPU address back through an out-parameter for the > >> dma_direct_alloc() caller. > >> > >> Fixes: 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool helper") > >> Cc: stable@vger.kernel.org > >> Tested-by: Michael Kelley > >> Tested-by: Mostafa Saleh > >> Reviewed-by: Jason Gunthorpe > >> Signed-off-by: Aneesh Kumar K.V (Arm) > >> --- > >> kernel/dma/direct.c | 18 ++++++++++-------- > >> 1 file changed, 10 insertions(+), 8 deletions(-) > >> > >> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > >> index d8219efe3273..363d984d90e7 100644 > >> --- a/kernel/dma/direct.c > >> +++ b/kernel/dma/direct.c > >> @@ -164,22 +164,21 @@ static bool dma_direct_use_pool(struct device *dev, gfp_t gfp) > >> return !gfpflags_allow_blocking(gfp) && !is_swiotlb_for_alloc(dev); > >> } > >> > >> -static void *dma_direct_alloc_from_pool(struct device *dev, size_t size, > >> - dma_addr_t *dma_handle, gfp_t gfp) > >> +static struct page *dma_direct_alloc_from_pool(struct device *dev, size_t size, > >> + dma_addr_t *dma_handle, void **cpu_addr, gfp_t gfp) > >> { > >> struct page *page; > >> u64 phys_limit; > >> - void *ret; > >> > >> if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_DMA_COHERENT_POOL))) > >> 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, cpu_addr, gfp, dma_coherent_ok); > >> if (!page) > >> return NULL; > >> *dma_handle = phys_to_dma_direct(dev, page_to_phys(page)); > >> - return ret; > >> + return page; > >> } > >> > >> static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size, > >> @@ -247,8 +246,11 @@ void *dma_direct_alloc(struct device *dev, size_t size, > >> * the atomic pools instead if we aren't allowed block. > >> */ > >> if ((remap || force_dma_unencrypted(dev)) && > >> - dma_direct_use_pool(dev, gfp)) > >> - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > >> + dma_direct_use_pool(dev, gfp)) { > >> + page = dma_direct_alloc_from_pool(dev, size, dma_handle, > >> + &ret, gfp); > >> + return page ? ret : NULL; > > > > Sorry for joining the discussion late, but the line above caught my > > attention. > > > > Why do we need both ret and page? We can derive cpu_addr from page and > > vice versa. Do we really need the &ret parameter? Or, more generally, do > > we really need "struct page *"? > > > > static struct page *__dma_alloc_from_pool(struct device *dev, size_t size, > > struct gen_pool *pool, void **cpu_addr, > > bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)) > > { > > ... > > *cpu_addr = (void *)addr; > > memset(*cpu_addr, 0, size); > > return pfn_to_page(__phys_to_pfn(phys)); > > } > > > > Why > > > > With CONFIG_DMA_DIRECT_REMAP the cpu_addr can be different from > page_address. Can you please point to the code there it can happen? __dma_alloc_from_pool() has direct connection between physical address and struct page. Thanks > > -aneesh >