| Message ID | 1c591836f1ec6e676a8889cdccd042650eadb73b.1442499554.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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
On 17/09/15 15:52, Will Deacon wrote: [...] >> -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? Can do for the sync and unmap cases - the alloc_pages one needs to avoid truncation in the comparison if dma_addr_t and phys_addr_t are different sizes, so can't safely cast one to the other either way. I can at least get rid of the u64 casts there though, as they seem superfluous after a bit of experimentation and another read of the good old "Usual arithmetic conversions". I'll fix up and repost. Robin. > > Will >
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)); -} - static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp, struct io_pgtable_cfg *cfg) { @@ -226,7 +221,7 @@ static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp, * address directly, so if the DMA layer suggests it can't by * giving us back some translation, that bodes very badly... */ - if (dma != __arm_lpae_dma_addr(dev, pages)) + if ((u64)dma != (u64)virt_to_phys(pages)) goto out_unmap; } @@ -246,7 +241,7 @@ static void __arm_lpae_free_pages(void *pages, size_t size, struct device *dev = cfg->iommu_dev; if (!selftest_running) - dma_unmap_single(dev, __arm_lpae_dma_addr(dev, pages), + dma_unmap_single(dev, (dma_addr_t)virt_to_phys(pages), size, DMA_TO_DEVICE); free_pages_exact(pages, size); } @@ -259,7 +254,7 @@ static void __arm_lpae_set_pte(arm_lpae_iopte *ptep, arm_lpae_iopte pte, *ptep = pte; if (!selftest_running) - dma_sync_single_for_device(dev, __arm_lpae_dma_addr(dev, ptep), + dma_sync_single_for_device(dev, (dma_addr_t)virt_to_phys(ptep), sizeof(pte), DMA_TO_DEVICE); } @@ -629,6 +624,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg) if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS) return NULL; + if (cfg->iommu_dev->dma_pfn_offset) { + dev_err(cfg->iommu_dev, "Cannot accommodate DMA offset for IOMMU page tables\n"); + return NULL; + } + data = kmalloc(sizeof(*data), GFP_KERNEL); if (!data) return NULL;
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. 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(-)