| Message ID | alpine.DEB.2.10.1704111411350.2759@sstabellini-ThinkPad-X260 (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Apr 11, 2017 at 04:39:09PM -0700, Stefano Stabellini wrote: > On Tue, 11 Apr 2017, Catalin Marinas wrote: > > On Tue, Apr 11, 2017 at 01:43:28PM +0100, Julien Grall wrote: > > > On 11/04/17 02:14, Bart Van Assche wrote: > > > > On 04/10/17 17:31, Stefano Stabellini wrote: > > > >> I think the reason is that, as you can see, if (dev && dev->dma_ops), > > > >> dev->dma_ops is returned, while before this changes, xen_dma_ops was > > > >> returned on Xen on ARM. > > > >> > > > >> Unfortunately DMA cannot work properly without using the appropriate > > > >> xen_dma_ops. See drivers/xen/swiotlb-xen.c and arch/arm/xen/mm.c for > > > >> more details. (The problem is easy to spot, but I wasn't CC'ed on the > > > >> patch.) > > > >> > > > >> I don't know how to solve this problem without introducing some sort of > > > >> if (xen()) in include/linux/dma-mapping.h. > > > > > > > > Sorry but I don't have access to an ARM development system. Does your > > > > comment apply to dev == NULL only, dev != NULL only or perhaps to both? > > > > If your comment applies to dev != NULL only, can you check whether > > > > adding something like set_dma_ops(dev, get_arch_dma_ops(NULL)) to the > > > > appropriate ARM arch_setup_dma_ops() function is sufficient? > > > > > > If I understand correctly, set_dma_ops will replace dev->dma_ops with > > > Xen DMA ops. [...] > > Yet another way would be for dom0 to always set dev->dma_ops to > > xen_dma_ops and preserve the real dma_ops somewhere under dev->archdata. > > You could intercept the arch_setup_dma_ops() function for this or use > > bus_register_notifier() (though I think the former is easier). The Xen > > code making use of the real dma_ops would have to dig them out from > > dev->archdata. > > This is a good suggestion, Catalin. Thank you. See below. Is that what > you have in mind? Julien could you test it, please? If it is the right > approach, I'll submit the patch properly and rename __generic_dma_ops to > xen_generic_dma_ops or something. It looks fine to me (subject to testing successfully).
Hi Stefano, Sorry for the late answer. On 12/04/17 00:39, Stefano Stabellini wrote: > On Tue, 11 Apr 2017, Catalin Marinas wrote: >> On Tue, Apr 11, 2017 at 01:43:28PM +0100, Julien Grall wrote: >>> On 11/04/17 02:14, Bart Van Assche wrote: >>>> On 04/10/17 17:31, Stefano Stabellini wrote: >>>>> I think the reason is that, as you can see, if (dev && dev->dma_ops), >>>>> dev->dma_ops is returned, while before this changes, xen_dma_ops was >>>>> returned on Xen on ARM. >>>>> >>>>> Unfortunately DMA cannot work properly without using the appropriate >>>>> xen_dma_ops. See drivers/xen/swiotlb-xen.c and arch/arm/xen/mm.c for >>>>> more details. (The problem is easy to spot, but I wasn't CC'ed on the >>>>> patch.) >>>>> >>>>> I don't know how to solve this problem without introducing some sort of >>>>> if (xen()) in include/linux/dma-mapping.h. >>>> >>>> Sorry but I don't have access to an ARM development system. Does your >>>> comment apply to dev == NULL only, dev != NULL only or perhaps to both? >>>> If your comment applies to dev != NULL only, can you check whether >>>> adding something like set_dma_ops(dev, get_arch_dma_ops(NULL)) to the >>>> appropriate ARM arch_setup_dma_ops() function is sufficient? >>> >>> If I understand correctly, set_dma_ops will replace dev->dma_ops with >>> Xen DMA ops. >>> >>> However, Xen DMA ops will need in some places to call the device >>> specific DMA ops (see __generic_dma_ops(...)). So I think replacing >>> dev->dma_ops is not a solution here. >>> >>> The hackish patch below is fixing the problem for both ARM64 and ARM32. >>> >>> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h >>> index 0977317c6835..43a73ddeec7a 100644 >>> --- a/include/linux/dma-mapping.h >>> +++ b/include/linux/dma-mapping.h >>> @@ -174,6 +174,8 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma, >>> #include <asm/dma-mapping.h> >>> static inline const struct dma_map_ops *get_dma_ops(struct device *dev) >>> { >>> + if (xen_initial_domain()) >>> + return xen_dma_ops; >>> if (dev && dev->dma_ops) >>> return dev->dma_ops; >>> return get_arch_dma_ops(dev ? dev->bus : NULL); >> >> If we do this, I guess there is no need to check for >> xen_initial_domain() in the get_arch_dma_ops() function. Anyway, this >> hunk would break the other architectures since xen_dma_ops is only >> defined for arm and arm64. >> >>> It is not nice as this is common code, but I can't find a better solution >>> so far. Any opinions? >> >> A different hack would be to avoid the generic get_dma_ops >> implementation on arm with some #ifdef hacks above. >> >> Yet another way would be for dom0 to always set dev->dma_ops to >> xen_dma_ops and preserve the real dma_ops somewhere under dev->archdata. >> You could intercept the arch_setup_dma_ops() function for this or use >> bus_register_notifier() (though I think the former is easier). The Xen >> code making use of the real dma_ops would have to dig them out from >> dev->archdata. > > This is a good suggestion, Catalin. Thank you. See below. Is that what > you have in mind? Julien could you test it, please? If it is the right > approach, I'll submit the patch properly and rename __generic_dma_ops to > xen_generic_dma_ops or something. This patch is fixing the bug I encountered. Cheers,
On Thu, 13 Apr 2017, Julien Grall wrote: > Hi Stefano, > > Sorry for the late answer. > > On 12/04/17 00:39, Stefano Stabellini wrote: > > On Tue, 11 Apr 2017, Catalin Marinas wrote: > > > On Tue, Apr 11, 2017 at 01:43:28PM +0100, Julien Grall wrote: > > > > On 11/04/17 02:14, Bart Van Assche wrote: > > > > > On 04/10/17 17:31, Stefano Stabellini wrote: > > > > > > I think the reason is that, as you can see, if (dev && > > > > > > dev->dma_ops), > > > > > > dev->dma_ops is returned, while before this changes, xen_dma_ops was > > > > > > returned on Xen on ARM. > > > > > > > > > > > > Unfortunately DMA cannot work properly without using the appropriate > > > > > > xen_dma_ops. See drivers/xen/swiotlb-xen.c and arch/arm/xen/mm.c for > > > > > > more details. (The problem is easy to spot, but I wasn't CC'ed on > > > > > > the > > > > > > patch.) > > > > > > > > > > > > I don't know how to solve this problem without introducing some sort > > > > > > of > > > > > > if (xen()) in include/linux/dma-mapping.h. > > > > > > > > > > Sorry but I don't have access to an ARM development system. Does your > > > > > comment apply to dev == NULL only, dev != NULL only or perhaps to > > > > > both? > > > > > If your comment applies to dev != NULL only, can you check whether > > > > > adding something like set_dma_ops(dev, get_arch_dma_ops(NULL)) to the > > > > > appropriate ARM arch_setup_dma_ops() function is sufficient? > > > > > > > > If I understand correctly, set_dma_ops will replace dev->dma_ops with > > > > Xen DMA ops. > > > > > > > > However, Xen DMA ops will need in some places to call the device > > > > specific DMA ops (see __generic_dma_ops(...)). So I think replacing > > > > dev->dma_ops is not a solution here. > > > > > > > > The hackish patch below is fixing the problem for both ARM64 and ARM32. > > > > > > > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > > > > index 0977317c6835..43a73ddeec7a 100644 > > > > --- a/include/linux/dma-mapping.h > > > > +++ b/include/linux/dma-mapping.h > > > > @@ -174,6 +174,8 @@ int dma_mmap_from_coherent(struct device *dev, > > > > struct vm_area_struct *vma, > > > > #include <asm/dma-mapping.h> > > > > static inline const struct dma_map_ops *get_dma_ops(struct device *dev) > > > > { > > > > + if (xen_initial_domain()) > > > > + return xen_dma_ops; > > > > if (dev && dev->dma_ops) > > > > return dev->dma_ops; > > > > return get_arch_dma_ops(dev ? dev->bus : NULL); > > > > > > If we do this, I guess there is no need to check for > > > xen_initial_domain() in the get_arch_dma_ops() function. Anyway, this > > > hunk would break the other architectures since xen_dma_ops is only > > > defined for arm and arm64. > > > > > > > It is not nice as this is common code, but I can't find a better > > > > solution > > > > so far. Any opinions? > > > > > > A different hack would be to avoid the generic get_dma_ops > > > implementation on arm with some #ifdef hacks above. > > > > > > Yet another way would be for dom0 to always set dev->dma_ops to > > > xen_dma_ops and preserve the real dma_ops somewhere under dev->archdata. > > > You could intercept the arch_setup_dma_ops() function for this or use > > > bus_register_notifier() (though I think the former is easier). The Xen > > > code making use of the real dma_ops would have to dig them out from > > > dev->archdata. > > > > This is a good suggestion, Catalin. Thank you. See below. Is that what > > you have in mind? Julien could you test it, please? If it is the right > > approach, I'll submit the patch properly and rename __generic_dma_ops to > > xen_generic_dma_ops or something. > > This patch is fixing the bug I encountered. I'll add your tested-by.
diff --git a/arch/arm/include/asm/device.h b/arch/arm/include/asm/device.h index 220ba20..36ec9c8 100644 --- a/arch/arm/include/asm/device.h +++ b/arch/arm/include/asm/device.h @@ -16,6 +16,9 @@ struct dev_archdata { #ifdef CONFIG_ARM_DMA_USE_IOMMU struct dma_iommu_mapping *mapping; #endif +#ifdef CONFIG_XEN + const struct dma_map_ops *dev_dma_ops; +#endif bool dma_coherent; }; diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index 7166569..680d3f3 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -16,19 +16,9 @@ extern const struct dma_map_ops arm_dma_ops; extern const struct dma_map_ops arm_coherent_dma_ops; -static inline const struct dma_map_ops *__generic_dma_ops(struct device *dev) -{ - if (dev && dev->dma_ops) - return dev->dma_ops; - return &arm_dma_ops; -} - static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus) { - if (xen_initial_domain()) - return xen_dma_ops; - else - return __generic_dma_ops(NULL); + return &arm_dma_ops; } #define HAVE_ARCH_DMA_SUPPORTED 1 diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 63eabb0..82d61eb 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -2396,6 +2396,11 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size, dma_ops = arm_get_dma_map_ops(coherent); set_dma_ops(dev, dma_ops); + + if (xen_initial_domain()) { + dev->archdata.dev_dma_ops = dev->dma_ops; + dev->dma_ops = xen_dma_ops; + } } void arch_teardown_dma_ops(struct device *dev) diff --git a/arch/arm64/include/asm/device.h b/arch/arm64/include/asm/device.h index 73d5bab..5a5fa47 100644 --- a/arch/arm64/include/asm/device.h +++ b/arch/arm64/include/asm/device.h @@ -20,6 +20,9 @@ struct dev_archdata { #ifdef CONFIG_IOMMU_API void *iommu; /* private IOMMU data */ #endif +#ifdef CONFIG_XEN + const struct dma_map_ops *dev_dma_ops; +#endif bool dma_coherent; }; diff --git a/arch/arm64/include/asm/dma-mapping.h b/arch/arm64/include/asm/dma-mapping.h index 505756c..5392dbe 100644 --- a/arch/arm64/include/asm/dma-mapping.h +++ b/arch/arm64/include/asm/dma-mapping.h @@ -27,11 +27,8 @@ #define DMA_ERROR_CODE (~(dma_addr_t)0) extern const struct dma_map_ops dummy_dma_ops; -static inline const struct dma_map_ops *__generic_dma_ops(struct device *dev) +static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus) { - if (dev && dev->dma_ops) - return dev->dma_ops; - /* * We expect no ISA devices, and all other DMA masters are expected to * have someone call arch_setup_dma_ops at device creation time. @@ -39,14 +36,6 @@ static inline const struct dma_map_ops *__generic_dma_ops(struct device *dev) return &dummy_dma_ops; } -static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus) -{ - if (xen_initial_domain()) - return xen_dma_ops; - else - return __generic_dma_ops(NULL); -} - void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size, const struct iommu_ops *iommu, bool coherent); #define arch_setup_dma_ops arch_setup_dma_ops diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c index 81cdb2e..e574c39 100644 --- a/arch/arm64/mm/dma-mapping.c +++ b/arch/arm64/mm/dma-mapping.c @@ -977,4 +977,9 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size, dev->archdata.dma_coherent = coherent; __iommu_setup_dma_ops(dev, dma_base, size, iommu); + + if (xen_initial_domain()) { + dev->archdata.dev_dma_ops = dev->dma_ops; + dev->dma_ops = xen_dma_ops; + } } diff --git a/include/xen/arm/page-coherent.h b/include/xen/arm/page-coherent.h index 95ce6ac..b0a2bfc 100644 --- a/include/xen/arm/page-coherent.h +++ b/include/xen/arm/page-coherent.h @@ -2,8 +2,16 @@ #define _ASM_ARM_XEN_PAGE_COHERENT_H #include <asm/page.h> +#include <asm/dma-mapping.h> #include <linux/dma-mapping.h> +static inline const struct dma_map_ops *__generic_dma_ops(struct device *dev) +{ + if (dev && dev->archdata.dev_dma_ops) + return dev->archdata.dev_dma_ops; + return get_arch_dma_ops(NULL); +} + void __xen_dma_map_page(struct device *hwdev, struct page *page, dma_addr_t dev_addr, unsigned long offset, size_t size, enum dma_data_direction dir, unsigned long attrs);