linux_kernel/arch/x86/kernel/pci-dma.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/dma-direct.h>
#include <linux/dma-debug.h>
#include <linux/dmar.h>
#include <linux/export.h>
#include <linux/bootmem.h>
#include <linux/gfp.h>
#include <linux/pci.h>

#include <asm/proto.h>
#include <asm/dma.h>
#include <asm/iommu.h>
#include <asm/gart.h>
#include <asm/calgary.h>
#include <asm/x86_init.h>
#include <asm/iommu_table.h>

static bool disable_dac_quirk __read_mostly;

const struct dma_map_ops *dma_ops = &dma_direct_ops;
EXPORT_SYMBOL(dma_ops);

#ifdef CONFIG_IOMMU_DEBUG
int panic_on_overflow __read_mostly = 1;
int force_iommu __read_mostly = 1;
#else
int panic_on_overflow __read_mostly = 0;
int force_iommu __read_mostly = 0;
#endif

int iommu_merge __read_mostly = 0;

int no_iommu __read_mostly;
/* Set this to 1 if there is a HW IOMMU in the system */
int iommu_detected __read_mostly = 0;

/*
 * This variable becomes 1 if iommu=pt is passed on the kernel command line.
 * If this variable is 1, IOMMU implementations do no DMA translation for
 * devices and allow every device to access to whole physical memory. This is
 * useful if a user wants to use an IOMMU only for KVM device assignment to
 * guests and not for driver dma translation.
 */
int iommu_pass_through __read_mostly;

extern struct iommu_table_entry __iommu_table[], __iommu_table_end[];

/* Dummy device used for NULL arguments (normally ISA). */
struct device x86_dma_fallback_dev = {
	.init_name = "fallback device",
	.coherent_dma_mask = ISA_DMA_BIT_MASK,
	.dma_mask = &x86_dma_fallback_dev.coherent_dma_mask,
};
EXPORT_SYMBOL(x86_dma_fallback_dev);

void __init pci_iommu_alloc(void)
{
	struct iommu_table_entry *p;

	sort_iommu_table(__iommu_table, __iommu_table_end);
	check_iommu_entries(__iommu_table, __iommu_table_end);

	for (p = __iommu_table; p < __iommu_table_end; p++) {
		if (p && p->detect && p->detect() > 0) {
			p->flags |= IOMMU_DETECTED;
			if (p->early_init)
				p->early_init();
			if (p->flags & IOMMU_FINISH_IF_DETECTED)
				break;
		}
	}
}

bool arch_dma_alloc_attrs(struct device **dev)
{
	if (!*dev)
		*dev = &x86_dma_fallback_dev;

	if (!is_device_dma_capable(*dev))
		return false;
	return true;

}
EXPORT_SYMBOL(arch_dma_alloc_attrs);

/*
 * See <Documentation/x86/x86_64/boot-options.txt> for the iommu kernel
 * parameter documentation.
 */
static __init int iommu_setup(char *p)
{
	iommu_merge = 1;

	if (!p)
		return -EINVAL;

	while (*p) {
		if (!strncmp(p, "off", 3))
			no_iommu = 1;
		/* gart_parse_options has more force support */
		if (!strncmp(p, "force", 5))
			force_iommu = 1;
		if (!strncmp(p, "noforce", 7)) {
			iommu_merge = 0;
			force_iommu = 0;
		}

		if (!strncmp(p, "biomerge", 8)) {
			iommu_merge = 1;
			force_iommu = 1;
		}
		if (!strncmp(p, "panic", 5))
			panic_on_overflow = 1;
		if (!strncmp(p, "nopanic", 7))
			panic_on_overflow = 0;
		if (!strncmp(p, "merge", 5)) {
			iommu_merge = 1;
			force_iommu = 1;
		}
		if (!strncmp(p, "nomerge", 7))
			iommu_merge = 0;
		if (!strncmp(p, "forcesac", 8))
			pr_warn("forcesac option ignored.\n");
		if (!strncmp(p, "allowdac", 8))
			pr_warn("allowdac option ignored.\n");
		if (!strncmp(p, "nodac", 5))
			pr_warn("nodac option ignored.\n");
		if (!strncmp(p, "usedac", 6)) {
			disable_dac_quirk = true;
			return 1;
		}
#ifdef CONFIG_SWIOTLB
		if (!strncmp(p, "soft", 4))
			swiotlb = 1;
#endif
		if (!strncmp(p, "pt", 2))
			iommu_pass_through = 1;

		gart_parse_options(p);

#ifdef CONFIG_CALGARY_IOMMU
		if (!strncmp(p, "calgary", 7))
			use_calgary = 1;
#endif /* CONFIG_CALGARY_IOMMU */

		p += strcspn(p, ",");
		if (*p == ',')
			++p;
	}
	return 0;
}
early_param("iommu", iommu_setup);

static int __init pci_iommu_init(void)
{
	struct iommu_table_entry *p;

#ifdef CONFIG_PCI
	dma_debug_add_bus(&pci_bus_type);
#endif
	x86_init.iommu.iommu_init();

	for (p = __iommu_table; p < __iommu_table_end; p++) {
		if (p && (p->flags & IOMMU_DETECTED) && p->late_init)
			p->late_init();
	}

	return 0;
}
/* Must execute after PCI subsystem */
rootfs_initcall(pci_iommu_init);

#ifdef CONFIG_PCI
/* Many VIA bridges seem to corrupt data for DAC. Disable it here */

static int via_no_dac_cb(struct pci_dev *pdev, void *data)
{
	pdev->dev.dma_32bit_limit = true;
	return 0;
}

static void via_no_dac(struct pci_dev *dev)
{
	if (!disable_dac_quirk) {
		dev_info(&dev->dev, "disabling DAC on VIA PCI bridge\n");
		pci_walk_bus(dev->subordinate, via_no_dac_cb, NULL);
	}
}
DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
				PCI_CLASS_BRIDGE_PCI, 8, via_no_dac);
#endif