1. 根目录:
2. arch
3. x86
4. xen
5. pci-swiotlb-xen.c

/* Glue code to lib/swiotlb-xen.c */

#include <linux/dma-mapping.h>
#include <linux/pci.h>
#include <xen/swiotlb-xen.h>

#include <asm/xen/hypervisor.h>
#include <xen/xen.h>
#include <asm/iommu_table.h>

int xen_swiotlb __read_mostly;

static struct dma_map_ops xen_swiotlb_dma_ops = {
	.mapping_error = xen_swiotlb_dma_mapping_error,
	.alloc = xen_swiotlb_alloc_coherent,
	.free = xen_swiotlb_free_coherent,
	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
	.map_sg = xen_swiotlb_map_sg_attrs,
	.unmap_sg = xen_swiotlb_unmap_sg_attrs,
	.map_page = xen_swiotlb_map_page,
	.unmap_page = xen_swiotlb_unmap_page,
	.dma_supported = xen_swiotlb_dma_supported,
};

/*
 * pci_xen_swiotlb_detect - set xen_swiotlb to 1 if necessary
 *
 * This returns non-zero if we are forced to use xen_swiotlb (by the boot
 * option).
 */
int __init pci_xen_swiotlb_detect(void)
{

	/* If running as PV guest, either iommu=soft, or swiotlb=force will
	 * activate this IOMMU. If running as PV privileged, activate it
	 * irregardless.
	 */
	if ((xen_initial_domain() || swiotlb || swiotlb_force) &&
	    (xen_pv_domain()))
		xen_swiotlb = 1;

	/* If we are running under Xen, we MUST disable the native SWIOTLB.
	 * Don't worry about swiotlb_force flag activating the native, as
	 * the 'swiotlb' flag is the only one turning it on. */
	if (xen_pv_domain())
		swiotlb = 0;

	return xen_swiotlb;
}

void __init pci_xen_swiotlb_init(void)
{
	if (xen_swiotlb) {
		xen_swiotlb_init(1);
		dma_ops = &xen_swiotlb_dma_ops;

		/* Make sure ACS will be enabled */
		pci_request_acs();
	}
}
IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
		  0,
		  pci_xen_swiotlb_init,
		  0);