From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Gibson Subject: Re: [PATCH 1/2] dma-mapping: Add dma_addr_is_phys_addr() Date: Mon, 14 Oct 2019 15:51:39 +1100 Message-ID: <20191014045139.GN4080__19174.5627600298$1571029720$gmane$org@umbus.fritz.box> References: <1570843519-8696-1-git-send-email-linuxram@us.ibm.com> <1570843519-8696-2-git-send-email-linuxram@us.ibm.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============4978440045942269506==" Return-path: In-Reply-To: <1570843519-8696-2-git-send-email-linuxram@us.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Ram Pai Cc: andmike@us.ibm.com, sukadev@linux.vnet.ibm.com, b.zolnierkie@samsung.com, mpe@ellerman.id.au, aik@linux.ibm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, paulus@ozlabs.org, iommu@lists.linux-foundation.org, paul.burton@mips.com, benh@kernel.crashing.org, m.szyprowski@samsung.com, linuxppc-dev@lists.ozlabs.org, hch@lst.de, robin.murphy@arm.com List-Id: virtualization@lists.linuxfoundation.org --===============4978440045942269506== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="0aF+6pWUK5w8WdCh" Content-Disposition: inline --0aF+6pWUK5w8WdCh Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Oct 11, 2019 at 06:25:18PM -0700, Ram Pai wrote: > From: Thiago Jung Bauermann >=20 > In order to safely use the DMA API, virtio needs to know whether DMA > addresses are in fact physical addresses and for that purpose, > dma_addr_is_phys_addr() is introduced. >=20 > cc: Benjamin Herrenschmidt > cc: David Gibson > cc: Michael Ellerman > cc: Paul Mackerras > cc: Michael Roth > cc: Alexey Kardashevskiy > cc: Paul Burton > cc: Robin Murphy > cc: Bartlomiej Zolnierkiewicz > cc: Marek Szyprowski > cc: Christoph Hellwig > Suggested-by: Michael S. Tsirkin > Signed-off-by: Ram Pai > Signed-off-by: Thiago Jung Bauermann The change itself looks ok, so Reviewed-by: David Gibson However, I would like to see the commit message (and maybe the inline comments) expanded a bit on what the distinction here is about. Some of the text from the next patch would be suitable, about DMA addresses usually being in a different address space but not in the case of bounce buffering. > --- > arch/powerpc/include/asm/dma-mapping.h | 21 +++++++++++++++++++++ > arch/powerpc/platforms/pseries/Kconfig | 1 + > include/linux/dma-mapping.h | 20 ++++++++++++++++++++ > kernel/dma/Kconfig | 3 +++ > 4 files changed, 45 insertions(+) >=20 > diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/includ= e/asm/dma-mapping.h > index 565d6f7..f92c0a4b 100644 > --- a/arch/powerpc/include/asm/dma-mapping.h > +++ b/arch/powerpc/include/asm/dma-mapping.h > @@ -5,6 +5,8 @@ > #ifndef _ASM_DMA_MAPPING_H > #define _ASM_DMA_MAPPING_H > =20 > +#include > + > static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type= *bus) > { > /* We don't handle the NULL dev case for ISA for now. We could > @@ -15,4 +17,23 @@ static inline const struct dma_map_ops *get_arch_dma_o= ps(struct bus_type *bus) > return NULL; > } > =20 > +#ifdef CONFIG_ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR > +/** > + * dma_addr_is_phys_addr - check whether a device DMA address is a physi= cal > + * address > + * @dev: device to check > + * > + * Returns %true if any DMA address for this device happens to also be a= valid > + * physical address (not necessarily of the same page). > + */ > +static inline bool dma_addr_is_phys_addr(struct device *dev) > +{ > + /* > + * Secure guests always use the SWIOTLB, therefore DMA addresses are > + * actually the physical address of the bounce buffer. > + */ > + return is_secure_guest(); > +} > +#endif > + > #endif /* _ASM_DMA_MAPPING_H */ > diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platfo= rms/pseries/Kconfig > index 9e35cdd..0108150 100644 > --- a/arch/powerpc/platforms/pseries/Kconfig > +++ b/arch/powerpc/platforms/pseries/Kconfig > @@ -152,6 +152,7 @@ config PPC_SVM > select SWIOTLB > select ARCH_HAS_MEM_ENCRYPT > select ARCH_HAS_FORCE_DMA_UNENCRYPTED > + select ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR > help > There are certain POWER platforms which support secure guests using > the Protected Execution Facility, with the help of an Ultravisor > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index f7d1eea..6df5664 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -693,6 +693,26 @@ static inline bool dma_addressing_limited(struct dev= ice *dev) > dma_get_required_mask(dev); > } > =20 > +#ifndef CONFIG_ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR > +/** > + * dma_addr_is_phys_addr - check whether a device DMA address is a physi= cal > + * address > + * @dev: device to check > + * > + * Returns %true if any DMA address for this device happens to also be a= valid > + * physical address (not necessarily of the same page). > + */ > +static inline bool dma_addr_is_phys_addr(struct device *dev) > +{ > + /* > + * Except in very specific setups, DMA addresses exist in a different > + * address space from CPU physical addresses and cannot be directly used > + * to reference system memory. > + */ > + return false; > +} > +#endif > + > #ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS > void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size, > const struct iommu_ops *iommu, bool coherent); > diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig > index 9decbba..6209b46 100644 > --- a/kernel/dma/Kconfig > +++ b/kernel/dma/Kconfig > @@ -51,6 +51,9 @@ config ARCH_HAS_DMA_MMAP_PGPROT > config ARCH_HAS_FORCE_DMA_UNENCRYPTED > bool > =20 > +config ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR > + bool > + > config DMA_NONCOHERENT_CACHE_SYNC > bool > =20 --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --0aF+6pWUK5w8WdCh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAl2j/tgACgkQbDjKyiDZ s5JjGg/+JngolQLtvjQamOxnEvRu2H1H2tVbqHMjiTaWHWflqa0S/1nocSzdtK2P XWHQwkku6xRMD2WmRLBxLciSfstKP0LO/s6GMh9ATx9JkDgaR1ayhMc1t6yIRrLh E1NNiwmwJBLNx4XDBV7ykagoSGaoF7LnOe2NFUeQ++IMMp61WYi95oc15s+JlEDG FGvfLDXYwLNyzhE7f8XQ11WLzdhj2oGey8n+Kjqg7yFmcYrw3H8aWet9tl8pL8wi QhATd99yJfC7Dwei+13Dg4b4ichGPn117SWXHd15FM6I6xkDOSwnq2nmCJOrcWrl jVOWHpgQHsdtizpdpc0RvjSXYjA5uXTOl5rOMz3/LVY/unvELd+7ohxL2miOb5fu PU26NMZXnL7Kc/vuvRemPvxYTX0RDH2JcOs8AmDaKWNony4yxqZENH2OUzkUQzuU 5sravuQc3pm7JiJKg3Qvb+30ufJkjRIhRWWRvUKBorR/rZnO4DrAWcmMD1Op4d7Y 1UHZTq3ebolz3NjC+n/OruacpccFEzfVst7LYVA7Ta0gNflF87Eskd66ANc3yCGZ eaeXmRyg+eQS8jdWsiZC0s+pftkVnKV1aR97WP9s7fUByOCrsO7Obzt9yAsjQC8p KynS5IvW4hY3deRymW3/sIX/qX+iWVm0z/7URc7CyskxWatq9xw= =/s/t -----END PGP SIGNATURE----- --0aF+6pWUK5w8WdCh-- --===============4978440045942269506== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization --===============4978440045942269506==--