linux/arch/x86/kernel/aperture_64.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Firmware replacement code.
 *
 * Work around broken BIOSes that don't set an aperture, only set the
 * aperture in the AGP bridge, or set too small aperture.
 *
 * If all fails map the aperture over some low memory.  This is cheaper than
 * doing bounce buffering. The memory is lost. This is done at early boot
 * because only the bootmem allocator can allocate 32+MB.
 *
 * Copyright 2002 Andi Kleen, SuSE Labs.
 */
#define pr_fmt(fmt) …

#include <linux/kernel.h>
#include <linux/kcore.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/memblock.h>
#include <linux/mmzone.h>
#include <linux/pci_ids.h>
#include <linux/pci.h>
#include <linux/bitops.h>
#include <linux/suspend.h>
#include <asm/e820/api.h>
#include <asm/io.h>
#include <asm/iommu.h>
#include <asm/gart.h>
#include <asm/pci-direct.h>
#include <asm/dma.h>
#include <asm/amd_nb.h>
#include <asm/x86_init.h>
#include <linux/crash_dump.h>

/*
 * Using 512M as goal, in case kexec will load kernel_big
 * that will do the on-position decompress, and could overlap with
 * the gart aperture that is used.
 * Sequence:
 * kernel_small
 * ==> kexec (with kdump trigger path or gart still enabled)
 * ==> kernel_small (gart area become e820_reserved)
 * ==> kexec (with kdump trigger path or gart still enabled)
 * ==> kerne_big (uncompressed size will be big than 64M or 128M)
 * So don't use 512M below as gart iommu, leave the space for kernel
 * code for safe.
 */
#define GART_MIN_ADDR …
#define GART_MAX_ADDR …

int gart_iommu_aperture;
int gart_iommu_aperture_disabled __initdata;
int gart_iommu_aperture_allowed __initdata;

int fallback_aper_order __initdata = …; /* 64MB */
int fallback_aper_force __initdata;

int fix_aperture __initdata = …;

#if defined(CONFIG_PROC_VMCORE) || defined(CONFIG_PROC_KCORE)
/*
 * If the first kernel maps the aperture over e820 RAM, the kdump kernel will
 * use the same range because it will remain configured in the northbridge.
 * Trying to dump this area via /proc/vmcore may crash the machine, so exclude
 * it from vmcore.
 */
static unsigned long aperture_pfn_start, aperture_page_count;

static int gart_mem_pfn_is_ram(unsigned long pfn)
{ … }

#ifdef CONFIG_PROC_VMCORE
static bool gart_oldmem_pfn_is_ram(struct vmcore_cb *cb, unsigned long pfn)
{ … }

static struct vmcore_cb gart_vmcore_cb = …;
#endif

static void __init exclude_from_core(u64 aper_base, u32 aper_order)
{ … }
#else
static void exclude_from_core(u64 aper_base, u32 aper_order)
{
}
#endif

/* This code runs before the PCI subsystem is initialized, so just
   access the northbridge directly. */

static u32 __init allocate_aperture(void)
{ … }


/* Find a PCI capability */
static u32 __init find_cap(int bus, int slot, int func, int cap)
{ … }

/* Read a standard AGPv3 bridge header */
static u32 __init read_agp(int bus, int slot, int func, int cap, u32 *order)
{ … }

/*
 * Look for an AGP bridge. Windows only expects the aperture in the
 * AGP bridge and some BIOS forget to initialize the Northbridge too.
 * Work around this here.
 *
 * Do an PCI bus scan by hand because we're running before the PCI
 * subsystem.
 *
 * All AMD AGP bridges are AGPv3 compliant, so we can do this scan
 * generically. It's probably overkill to always scan all slots because
 * the AGP bridges should be always an own bus on the HT hierarchy,
 * but do it here for future safety.
 */
static u32 __init search_agp_bridge(u32 *order, int *valid_agp)
{ … }

static bool gart_fix_e820 __initdata = …;

static int __init parse_gart_mem(char *p)
{ … }
early_param(…);

/*
 * With kexec/kdump, if the first kernel doesn't shut down the GART and the
 * second kernel allocates a different GART region, there might be two
 * overlapping GART regions present:
 *
 * - the first still used by the GART initialized in the first kernel.
 * - (sub-)set of it used as normal RAM by the second kernel.
 *
 * which leads to memory corruptions and a kernel panic eventually.
 *
 * This can also happen if the BIOS has forgotten to mark the GART region
 * as reserved.
 *
 * Try to update the e820 map to mark that new region as reserved.
 */
void __init early_gart_iommu_check(void)
{ … }

static int __initdata printed_gart_size_msg;

void __init gart_iommu_hole_init(void)
{ … }