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xen/swiotlb: don't initialize swiotlb twice on arm64 

On arm64 swiotlb is often (not always) already initialized by mem_init.
We don't want to initialize it twice, which would trigger a second
memory allocation. Moreover, the second memory pool is typically made of
high pages and ends up replacing the original memory pool of low pages.
As a side effect of this change, it is possible to have low pages in
swiotlb-xen on arm64.

Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Stefano Stabellini 2019-05-28 15:48:22 -07:00 committed by Konrad Rzeszutek Wilk
parent 063b8271ec
commit 4e7372e0dc
1 changed files with 11 additions and 1 deletions
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12
drivers/xen/swiotlb-xen.c
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@ -211,6 +211,15 @@ int __ref xen_swiotlb_init(int verbose, bool early)
retry:
bytes = xen_set_nslabs(xen_io_tlb_nslabs);
order = get_order(xen_io_tlb_nslabs << IO_TLB_SHIFT);
/*
* IO TLB memory already allocated. Just use it.
*/
if (io_tlb_start != 0) {
xen_io_tlb_start = phys_to_virt(io_tlb_start);
goto end;
}
/*
* Get IO TLB memory from any location.
*/
@ -237,7 +246,6 @@ int __ref xen_swiotlb_init(int verbose, bool early)
m_ret = XEN_SWIOTLB_ENOMEM;
goto error;
}
xen_io_tlb_end = xen_io_tlb_start + bytes;
/*
* And replace that memory with pages under 4GB.
*/
@ -264,6 +272,8 @@ int __ref xen_swiotlb_init(int verbose, bool early)
} else
rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);
end:
xen_io_tlb_end = xen_io_tlb_start + bytes;
if (!rc)
swiotlb_set_max_segment(PAGE_SIZE);