From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx138.postini.com [74.125.245.138]) by kanga.kvack.org (Postfix) with SMTP id 129316B002B for ; Tue, 16 Oct 2012 18:54:27 -0400 (EDT) Received: by mail-pa0-f41.google.com with SMTP id fa10so7238226pad.14 for ; Tue, 16 Oct 2012 15:54:26 -0700 (PDT) References: <20121016090434.7d5e088152a3e0b0606903c8@nvidia.com> <20121016.171338.1300372057637804407.hdoyu@nvidia.com> In-Reply-To: <20121016.171338.1300372057637804407.hdoyu@nvidia.com> Mime-Version: 1.0 (1.0) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=euc-kr Message-Id: From: Inki Dae Subject: Re: [Linaro-mm-sig] [RFC 0/2] DMA-mapping & IOMMU - physically contiguous allocations Date: Wed, 17 Oct 2012 07:54:17 +0900 Sender: owner-linux-mm@kvack.org List-ID: To: Hiroshi Doyu Cc: "inki.dae@samsung.com" , "m.szyprowski@samsung.com" , "linux@arm.linux.org.uk" , "arnd@arndb.de" , "linux-kernel@vger.kernel.org" , "linaro-mm-sig@lists.linaro.org" , "linux-mm@kvack.org" , "kyungmin.park@samsung.com" , "linux-arm-kernel@lists.infradead.org" , "linux-tegra@vger.kernel.org" Hi Hiroshi, 2012. 10. 16. =BF=C0=C8=C4 11:13 Hiroshi Doyu =C0=DB=BC=BA= : > Hi Inki, >=20 > Inki Dae wrote @ Tue, 16 Oct 2012 12:12:49 +0200: >=20 >> Hi Hiroshi, >>=20 >> 2012/10/16 Hiroshi Doyu : >>> Hi Inki/Marek, >>>=20 >>> On Tue, 16 Oct 2012 02:50:16 +0200 >>> Inki Dae wrote: >>>=20 >>>> 2012/10/15 Marek Szyprowski : >>>>> Hello, >>>>>=20 >>>>> Some devices, which have IOMMU, for some use cases might require to >>>>> allocate a buffers for DMA which is contiguous in physical memory. Suc= h >>>>> use cases appears for example in DRM subsystem when one wants to impro= ve >>>>> performance or use secure buffer protection. >>>>>=20 >>>>> I would like to ask if adding a new attribute, as proposed in this RFC= >>>>> is a good idea? I feel that it might be an attribute just for a single= >>>>> driver, but I would like to know your opinion. Should we look for othe= r >>>>> solution? >>>>>=20 >>>>=20 >>>> In addition, currently we have worked dma-mapping-based iommu support >>>> for exynos drm driver with this patch set so this patch set has been >>>> tested with iommu enabled exynos drm driver and worked fine. actually, >>>> this feature is needed for secure mode such as TrustZone. in case of >>>> Exynos SoC, memory region for secure mode should be physically >>>> contiguous and also maybe OMAP but now dma-mapping framework doesn't >>>> guarantee physically continuous memory allocation so this patch set >>>> would make it possible. >>>=20 >>> Agree that the contigous memory allocation is necessary for us too. >>>=20 >>> In addition to those contiguous/discontiguous page allocation, is >>> there any way to _import_ anonymous pages allocated by a process to be >>> used in dma-mapping API later? >>>=20 >>> I'm considering the following scenario, an user process allocates a >>> buffer by malloc() in advance, and then it asks some driver to convert >>> that buffer into IOMMU'able/DMA'able ones later. In this case, pages >>> are discouguous and even they may not be yet allocated at >>> malloc()/mmap(). >>>=20 >>=20 >> I'm not sure I understand what you mean but we had already tried this >> way and for this, you can refer to below link, >> http://www.mail-archive.com/dri-devel@lists.freedesktop.org= /msg22555.html >=20 > The above patch doesn't seem to have so much platform/SoC specific > code but rather it could common over other SoC as well. Is there any > plan to make it more generic, which can be used by other DRM drivers? >=20 Right, the above patch has no any platform/SoC specific code but doesn't use= dma-mapping API . Anyway we should refrain from using such thing because ge= m object could still be used and shared with other processes even if user pr= ocess freed user region allocated by malloc() And our new patch in progress would resolve this issue and this way is simil= ar to drm-based via driver of mainline kernel. And this patch isn't consider= ed for common use and is specific to platform/SoC so much. The pages backed c= an be used only by 2d gpu's dma. Thanks, Inki Dae > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org