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Date: Thu, 13 Apr 2017 12:21:25 +0100 From: Robin Murphy <robin.murphy@....com> To: Nate Watterson <nwatters@...eaurora.org>, Joerg Roedel <joro@...tes.org>, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Cc: shankerd@...eaurora.org Subject: Re: [PATCH] iommu/dma: Setup iova_domain granule for IOMMU_DMA_MSI cookies Hi Nate, On 13/04/17 09:55, Nate Watterson wrote: > Currently, the __iommu_dma_{map/free} functions call iova_{offset/align} > making them unsuitable for use with iommu_domains having an IOMMU_DMA_MSI > cookie since the cookie's iova_domain member, iovad, is uninitialized. > > Now that iommu_dma_get_msi_page() calls __iommu_dma_map() regardless > of cookie type, failures are being seen when mapping MSI target > addresses for devices attached to UNMANAGED domains. To work around > this issue, the iova_domain granule for IOMMU_DMA_MSI cookies is > initialized to the value returned by cookie_msi_granule(). Oh bum. Thanks for the report. However, I really don't like bodging around it with deliberate undefined behaviour. Fixing things properly doesn't seem too hard: ----->8----- diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 8348f366ddd1..62618e77bedc 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -396,13 +396,13 @@ static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie, dma_addr_t iova, size_t size) { struct iova_domain *iovad = &cookie->iovad; - unsigned long shift = iova_shift(iovad); /* The MSI case is only ever cleaning up its most recent allocation */ if (cookie->type == IOMMU_DMA_MSI_COOKIE) cookie->msi_iova -= size; else - free_iova_fast(iovad, iova >> shift, size >> shift); + free_iova_fast(iovad, iova_pfn(iovad, iova), + size >> iova_shift(iovad)); } static void __iommu_dma_unmap(struct iommu_domain *domain, dma_addr_t dma_addr, @@ -617,11 +617,14 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys, { struct iommu_domain *domain = iommu_get_domain_for_dev(dev); struct iommu_dma_cookie *cookie = domain->iova_cookie; - struct iova_domain *iovad = &cookie->iovad; - size_t iova_off = iova_offset(iovad, phys); + size_t iova_off = 0; dma_addr_t iova; - size = iova_align(iovad, size + iova_off); + if (cookie->type == IOMMU_DMA_IOVA_COOKIE) { + iova_off = iova_offset(&cookie->iovad, phys); + size = iova_align(&cookie->iovad, size + iova_off); + } + iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev), dev); if (!iova) return DMA_ERROR_CODE; -----8<----- Untested, and you'll probably want to double-check it anyway given that the original oversight was mine in the first place ;) Robin. > Fixes: a44e6657585b ("iommu/dma: Clean up MSI IOVA allocation") > Signed-off-by: Nate Watterson <nwatters@...eaurora.org> > --- > drivers/iommu/dma-iommu.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 8348f366..d7b0816 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -127,6 +127,16 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base) > > cookie->msi_iova = base; > domain->iova_cookie = cookie; > + > + /* > + * Setup granule for compatibility with __iommu_dma_{alloc/free} and > + * add a compile time check to ensure that writing granule won't > + * clobber msi_iova. > + */ > + cookie->iovad.granule = cookie_msi_granule(cookie); > + BUILD_BUG_ON(offsetof(struct iova_domain, granule) < > + sizeof(cookie->msi_iova)); > + > return 0; > } > EXPORT_SYMBOL(iommu_get_msi_cookie); >
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