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xen_dma_unmap_page, xen_dma_sync_single_for_cpu and
xen_dma_sync_single_for_device are currently implemented by calling into
the corresponding generic ARM implementation of these functions. In
order to do this, firstly the dma_addr_t handle, that on Xen is a
machine address, needs to be translated into a physical address. The
operation is expensive and inaccurate, given that a single machine
address can correspond to multiple physical addresses in one domain,
because the same page can be granted multiple times by the frontend.
To avoid this problem, we introduce a Xen specific implementation of
xen_dma_unmap_page, xen_dma_sync_single_for_cpu and
xen_dma_sync_single_for_device, that can operate on machine addresses
directly.
The new implementation relies on the fact that the hypervisor creates a
second p2m mapping of any grant pages at physical address == machine
address of the page for dom0. Therefore we can access memory at physical
address == dma_addr_r handle and perform the cache flushing there. Some
cache maintenance operations require a virtual address. Instead of using
ioremap_cache, that is not safe in interrupt context, we allocate a
per-cpu PAGE_KERNEL scratch page and we manually update the pte for it.
arm64 doesn't need cache maintenance operations on unmap for now.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Tested-by: Denis Schneider <v1ne2go@gmail.com>
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Xen on arm and arm64 needs SWIOTLB_XEN: when running on Xen we need to
program the hardware with mfns rather than pfns for dma addresses.
Remove SWIOTLB_XEN dependency on X86 and PCI and make XEN select
SWIOTLB_XEN on arm and arm64.
At the moment always rely on swiotlb-xen, but when Xen starts supporting
hardware IOMMUs we'll be able to avoid it conditionally on the presence
of an IOMMU on the platform.
Implement xen_create_contiguous_region on arm and arm64: for the moment
we assume that dom0 has been mapped 1:1 (physical addresses == machine
addresses) therefore we don't need to call XENMEM_exchange. Simply
return the physical address as dma address.
Initialize the xen-swiotlb from xen_early_init (before the native
dma_ops are initialized), set xen_dma_ops to &xen_swiotlb_dma_ops.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Changes in v8:
- assume dom0 is mapped 1:1, no need to call XENMEM_exchange.
Changes in v7:
- call __set_phys_to_machine_multi from xen_create_contiguous_region and
xen_destroy_contiguous_region to update the P2M;
- don't call XENMEM_unpin, it has been removed;
- call XENMEM_exchange instead of XENMEM_exchange_and_pin;
- set nr_exchanged to 0 before calling the hypercall.
Changes in v6:
- introduce and export xen_dma_ops;
- call xen_mm_init from as arch_initcall.
Changes in v4:
- remove redefinition of DMA_ERROR_CODE;
- update the code to use XENMEM_exchange_and_pin and XENMEM_unpin;
- add a note about hardware IOMMU in the commit message.
Changes in v3:
- code style changes;
- warn on XENMEM_put_dma_buf failures.
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Introduce physical to machine and machine to physical tracking
mechanisms based on rbtrees for arm/xen and arm64/xen.
We need it because any guests on ARM are an autotranslate guests,
therefore a physical address is potentially different from a machine
address. When programming a device to do DMA, we need to be
extra-careful to use machine addresses rather than physical addresses to
program the device. Therefore we need to know the physical to machine
mappings.
For the moment we assume that dom0 starts with a 1:1 physical to machine
mapping, in other words physical addresses correspond to machine
addresses. However when mapping a foreign grant reference, obviously the
1:1 model doesn't work anymore. So at the very least we need to be able
to track grant mappings.
We need locking to protect accesses to the two trees.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Changes in v8:
- move pfn_to_mfn and mfn_to_pfn to page.h as static inline functions;
- no need to walk the tree if phys_to_mach.rb_node is NULL;
- correctly handle multipage p2m entries;
- substitute the spin_lock with a rwlock.
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Changes in v2:
- return -ENOSYS rather than -1.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Use r12 to pass the hypercall number to the hypervisor.
We need a register to pass the hypercall number because we might not
know it at compile time and HVC only takes an immediate argument.
Among the available registers r12 seems to be the best choice because it
is defined as "intra-procedure call scratch register".
Use the ISS to pass an hypervisor specific tag.
Changes in v2:
- define an HYPERCALL macro for 5 arguments hypercall wrappers, even if
at the moment is unused;
- use ldm instead of pop;
- fix up comments.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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- Basic hypervisor.h and interface.h definitions.
- Skeleton enlighten.c, set xen_start_info to an empty struct.
- Make xen_initial_domain dependent on the SIF_PRIVILIGED_BIT.
The new code only compiles when CONFIG_XEN is set, that is going to be
added to arch/arm/Kconfig in patch #11 "xen/arm: introduce CONFIG_XEN on
ARM".
Changes in v3:
- improve comments.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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