Re: [PATCH v8 0/19] enable swiotlb-xen on arm and arm64

From: Konrad Rzeszutek Wilk
Date: Wed Oct 23 2013 - 10:16:44 EST

Next message: Frederic Weisbecker: "Re: perf events ring buffer memory barrier on powerpc"
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In reply to: Stefano Stabellini: "[PATCH v8 12/19] xen: introduce xen_dma_map/unmap_page and xen_dma_sync_single_for_cpu/device"
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On Thu, Oct 17, 2013 at 06:42:18PM +0100, Stefano Stabellini wrote:
> Hi all,
> this patch series enables xen-swiotlb on arm and arm64.
>
> It has been heavily reworked compared to the previous versions in order
> to achieve better performances and to address review comments.
>
> We are not using dma_mark_clean to ensure coherency anymore. We call the
> platform implementation of map_page and unmap_page.
>
> We assume that dom0 has been mapped 1:1 (physical address ==
> machine address), that is what Xen on ARM currently does.
> As a consequence we only use the swiotlb to handle dma
> requests involving pages corresponding to grant refs. Obviously these
> pages cannot be part of the 1:1 because they belong to another domain.
>
> To improve code readability this version of the series introduces a
> "p2m" for arm and arm64, implemented using two red-black trees. The p2m
> tracks physical to machine and machine to physical mappings. Given that
> we assume a 1:1 mapping in dom0, the only entries in both trees are
> grant refs that have been mapped in dom0.
>
> Another consequence of the new approach is that the hypercalls we were
> previously introducing (XENMEM_exchange_and_pin, XENMEM_pin,
> XENMEM_unpin) are not needed anymore.
> This latest version doesn't need any hypervisor changes anymore.

>From the Xen and SWIOTLB I am ok with the patch series, except
for these two patches:

swiotlb-xen: no need to do execute two bus_to_phys translations in a ..
swiotlb-xen: use xen_dma_map/unmap_page, xen_dma_sync_single_for_cpu/device

which I think need a bit more of explanation. In worst case they can be

#ifdef CONFIG_ARM
..
#endif

albeit that will need to be fixed in the future to remove the #ifdef I think.

>
> Cheers,
>
> Stefano
>
>
> Changes in v8:
> - use __phys_to_pfn and __pfn_to_phys in phys_to_dma and dma_to_phys;
> - cast 0 to dma_addr_t in the definition of DMA_ERROR_CODE;
> - move pfn_to_mfn and mfn_to_pfn to page.h as static inline functions;
> - no need to walk the two p2m trees if phys_to_mach.rb_node is NULL;
> - correctly handle multipage p2m entries;
> - substitute the p2m spin_lock with a rwlock;
> - assume dom0 is mapped 1:1, no need to call XENMEM_exchange in
> xen_create_contiguous_region;
> - add two simple performance improvements for swiotlb-xen.
>
> Changes in v7:
> - dma_mark_clean: switch to an empty implementation (we are going to use
> the platform map_page and unmap_page to ensure coherency);
> - dma_capable: use coherent_dma_mask if dma_mask hasn't been
> allocated;
> - introduce a p2m for xen on arm and arm64;
> - call __set_phys_to_machine_multi from xen_create_contiguous_region to
> update the p2m;
> - remove XENMEM_unpin and XENMEM_exchange_and_pin;
> - set nr_exchanged to 0 before calling the hypercall;
> - return xen_dma_ops only if we are the initial domain;
> - rename __get_dma_ops to __generic_dma_ops;
> - call __generic_dma_ops(hwdev)->alloc/free on arm64 too;
> - introduce xen_dma_map/unmap_page and xen_dma_sync_single_for_cpu/device;
> - use xen_dma_map/unmap_page, xen_dma_sync_single_for_cpu/device in
> swiotlb-xen;
> - use dev_warn instead of pr_warn;
> - remove the extra autotranslate check in biomerge.c;
> - call set_phys_to_machine after mapping grant refs in gnttab_map_refs;
> - call set_phys_to_machine after unmapping grant refs in gnttab_unmap_refs;
> - allow __set_phys_to_machine to be called for autotranslate guests on
> x86.
>
> Changes in v6:
> - check for dev->dma_mask being NULL in dma_capable;
> - update the comments and the hypercalls structures;
> - add a xen_dma_info entry to the rbtree in xen_swiotlb_alloc_coherent
> to keep track of the new mapping. Free the entry in xen_swiotlb_free_coherent;
> - rename xen_dma_seg to dma_info in xen_swiotlb_alloc/free_coherent to
> avoid confusions;
> - introduce and export xen_dma_ops;
> - call xen_mm_init from as arch_initcall;
> - call __get_dma_ops to get the native dma_ops pointer on arm;
> - do not merge biovecs;
> - add single page optimization: pin the page rather than bouncing.
>
> Changes in v5:
> - dropped the first two patches, already in the Xen tree;
> - implement dma_mark_clean using dmac_flush_range on arm;
> - add "arm64: define DMA_ERROR_CODE"
> - better comment for XENMEM_exchange_and_pin return codes;
> - fix xen_dma_add_entry error path;
> - remove the spin_lock: the red-black tree is not modified at run time;
> - add "swiotlb-xen: introduce xen_swiotlb_set_dma_mask";
> - add "xen: introduce xen_alloc/free_coherent_pages";
> - add "swiotlb-xen: use xen_alloc/free_coherent_pages";
> - add "swiotlb: don't assume that io_tlb_start-io_tlb_end is coherent".
>
> Changes in v4:
> - rename XENMEM_get_dma_buf to XENMEM_exchange_and_pin;
> - rename XENMEM_put_dma_buf to XENMEM_unpin;
> - improve the documentation of the new hypercalls;
> - add a note about out.address_bits for XENMEM_exchange;
> - code style fixes;
> - add err_out label in xen_dma_add_entry;
> - remove INVALID_ADDRESS, use DMA_ERROR_CODE instead;
> - add in-code comments regarding the usage of xen_dma_seg[0].dma_addr.
>
> Changes in v3:
> - add a patch to compile SWIOTLB without CONFIG_NEED_SG_DMA_LENGTH;
> - add a patch to compile SWIOTLB_XEN without CONFIG_NEED_SG_DMA_LENGTH;
> - arm/dma_capable: do not treat dma_mask as a limit;
> - arm/dmabounce: keep using arm_dma_ops;
> - add missing __init in xen_early_init declaration;
> - many code style and name changes in swiotlb-xen.c;
> - improve error checks in xen_dma_add_entry;
> - warn on XENMEM_put_dma_buf failures.
>
> Changes in v2:
> - fixed a couple of errors in xen_bus_to_phys, xen_phys_to_bus and
> xen_swiotlb_fixup.
>
>
>
>
> Julien Grall (1):
> ASoC: Samsung: Rename dma_ops by samsung_dma_ops
>
> Stefano Stabellini (18):
> arm: make SWIOTLB available
> arm64: define DMA_ERROR_CODE
> arm/xen,arm64/xen: introduce p2m
> xen/x86: allow __set_phys_to_machine for autotranslate guests
> xen: make xen_create_contiguous_region return the dma address
> xen/arm,arm64: enable SWIOTLB_XEN
> swiotlb-xen: introduce xen_swiotlb_set_dma_mask
> arm/xen: get_dma_ops: return xen_dma_ops if we are running as xen_initial_domain
> arm64/xen: get_dma_ops: return xen_dma_ops if we are running as xen_initial_domain
> xen: introduce xen_alloc/free_coherent_pages
> swiotlb-xen: use xen_alloc/free_coherent_pages
> xen: introduce xen_dma_map/unmap_page and xen_dma_sync_single_for_cpu/device
> swiotlb-xen: use xen_dma_map/unmap_page, xen_dma_sync_single_for_cpu/device
> swiotlb: print a warning when the swiotlb is full
> arm,arm64: do not always merge biovec if we are running on Xen
> grant-table: call set_phys_to_machine after mapping grant refs
> swiotlb-xen: no need to do execute two bus_to_phys translations in a row
> swiotlb-xen: static inline xen_phys_to_bus, xen_bus_to_phys, xen_virt_to_bus and range_straddles_page_boundary
>
> arch/arm/Kconfig | 7 +
> arch/arm/include/asm/dma-mapping.h | 50 +++++++-
> arch/arm/include/asm/io.h | 8 +
> arch/arm/include/asm/xen/hypervisor.h | 2 +
> arch/arm/include/asm/xen/page-coherent.h | 50 +++++++
> arch/arm/include/asm/xen/page.h | 50 ++++++-
> arch/arm/xen/Makefile | 2 +-
> arch/arm/xen/mm.c | 65 +++++++++
> arch/arm/xen/p2m.c | 208 ++++++++++++++++++++++++++++
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/dma-mapping.h | 14 ++-
> arch/arm64/include/asm/io.h | 9 ++
> arch/arm64/include/asm/xen/page-coherent.h | 47 +++++++
> arch/arm64/xen/Makefile | 2 +-
> arch/ia64/include/asm/xen/page-coherent.h | 38 +++++
> arch/x86/include/asm/xen/page-coherent.h | 38 +++++
> arch/x86/xen/mmu.c | 11 +-
> arch/x86/xen/p2m.c | 6 +-
> drivers/xen/Kconfig | 1 -
> drivers/xen/grant-table.c | 17 ++-
> drivers/xen/swiotlb-xen.c | 116 ++++++++++++----
> include/xen/swiotlb-xen.h | 2 +
> include/xen/xen-ops.h | 7 +-
> lib/swiotlb.c | 1 +
> sound/soc/samsung/dma.c | 4 +-
> 25 files changed, 704 insertions(+), 52 deletions(-)
> create mode 100644 arch/arm/include/asm/xen/page-coherent.h
> create mode 100644 arch/arm/xen/mm.c
> create mode 100644 arch/arm/xen/p2m.c
> create mode 100644 arch/arm64/include/asm/xen/page-coherent.h
> create mode 100644 arch/ia64/include/asm/xen/page-coherent.h
> create mode 100644 arch/x86/include/asm/xen/page-coherent.h
>
>
> git://git.kernel.org/pub/scm/linux/kernel/git/sstabellini/xen.git swiotlb-xen-8
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Next message: Frederic Weisbecker: "Re: perf events ring buffer memory barrier on powerpc"
Previous message: Frank Haverkamp: "Re: [PATCH] Generic WorkQueue Engine (GenWQE) device driver"
In reply to: Stefano Stabellini: "[PATCH v8 12/19] xen: introduce xen_dma_map/unmap_page and xen_dma_sync_single_for_cpu/device"
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