From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] iommu/io-pgtable-arm: Don't use dma_to_phys()
Date: Thu, 17 Sep 2015 15:52:17 +0100 [thread overview]
Message-ID: <20150917145216.GJ25634@arm.com> (raw)
In-Reply-To: <1c591836f1ec6e676a8889cdccd042650eadb73b.1442499554.git.robin.murphy@arm.com>
On Thu, Sep 17, 2015 at 03:22:20PM +0100, Robin Murphy wrote:
> In checking whether DMA addresses differ from physical addresses, using
> dma_to_phys() is actually the wrong thing to do, since it may hide any
> DMA offset, which is precisely one of the things we are checking for.
> Simply casting between the two address types, whilst ugly, is in fact
> the appropriate course of action.
Urgh... yes.
> We can also reject any device with a fixed DMA offset up-front at page
> table creation, leaving the allocation-time check for the more subtle
> cases like bounce buffering due to an incorrect DMA mask.
>
> Furthermore, we can then fix the hackish KConfig dependency so that
> architectures without a dma_to_phys() implementation may still
> COMPILE_TEST (or even use!) the code. The true dependency is on the
> DMA API, so use the appropriate symbol for that.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm•com>
> ---
> drivers/iommu/Kconfig | 3 +--
> drivers/iommu/io-pgtable-arm.c | 16 ++++++++--------
> 2 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 4664c2a..3dc1bcb 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -23,8 +23,7 @@ config IOMMU_IO_PGTABLE
> config IOMMU_IO_PGTABLE_LPAE
> bool "ARMv7/v8 Long Descriptor Format"
> select IOMMU_IO_PGTABLE
> - # SWIOTLB guarantees a dma_to_phys() implementation
> - depends on ARM || ARM64 || (COMPILE_TEST && SWIOTLB)
> + depends on HAS_DMA && (ARM || ARM64 || COMPILE_TEST)
> help
> Enable support for the ARM long descriptor pagetable format.
> This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 73c0748..e7f9ab9 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -202,11 +202,6 @@ typedef u64 arm_lpae_iopte;
>
> static bool selftest_running = false;
>
> -static dma_addr_t __arm_lpae_dma_addr(struct device *dev, void *pages)
> -{
> - return phys_to_dma(dev, virt_to_phys(pages));
> -}
Can we keep this helper kicking around, at least to contain the ugliness
of the virt_to_phys + cast?
Will
next prev parent reply other threads:[~2015-09-17 14:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-17 14:22 [PATCH] iommu/io-pgtable-arm: Don't use dma_to_phys() Robin Murphy
2015-09-17 14:52 ` Will Deacon [this message]
2015-09-17 15:53 ` Robin Murphy
2015-09-17 16:42 ` [PATCH v2] " Robin Murphy
2015-09-18 8:55 ` Yong Wu
2015-09-18 11:04 ` Robin Murphy
2015-09-18 12:29 ` Russell King - ARM Linux
2015-09-22 13:25 ` Yong Wu
2015-09-22 16:23 ` Robin Murphy
2015-09-22 16:26 ` Will Deacon
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