linux_kernel/arch/x86/xen/grant-table.c

// SPDX-License-Identifier: GPL-2.0 OR MIT
/******************************************************************************
 * grant_table.c
 * x86 specific part
 *
 * Granting foreign access to our memory reservation.
 *
 * Copyright (c) 2005-2006, Christopher Clark
 * Copyright (c) 2004-2005, K A Fraser
 * Copyright (c) 2008 Isaku Yamahata <yamahata at valinux co jp>
 *                    VA Linux Systems Japan. Split out x86 specific part.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include <xen/interface/xen.h>
#include <xen/page.h>
#include <xen/grant_table.h>
#include <xen/xen.h>

#include <asm/pgtable.h>

static struct gnttab_vm_area {
	struct vm_struct *area;
	pte_t **ptes;
} gnttab_shared_vm_area, gnttab_status_vm_area;

int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
			   unsigned long max_nr_gframes,
			   void **__shared)
{
	void *shared = *__shared;
	unsigned long addr;
	unsigned long i;

	if (shared == NULL)
		*__shared = shared = gnttab_shared_vm_area.area->addr;

	addr = (unsigned long)shared;

	for (i = 0; i < nr_gframes; i++) {
		set_pte_at(&init_mm, addr, gnttab_shared_vm_area.ptes[i],
			   mfn_pte(frames[i], PAGE_KERNEL));
		addr += PAGE_SIZE;
	}

	return 0;
}

int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
			   unsigned long max_nr_gframes,
			   grant_status_t **__shared)
{
	grant_status_t *shared = *__shared;
	unsigned long addr;
	unsigned long i;

	if (shared == NULL)
		*__shared = shared = gnttab_status_vm_area.area->addr;

	addr = (unsigned long)shared;

	for (i = 0; i < nr_gframes; i++) {
		set_pte_at(&init_mm, addr, gnttab_status_vm_area.ptes[i],
			   mfn_pte(frames[i], PAGE_KERNEL));
		addr += PAGE_SIZE;
	}

	return 0;
}

void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
{
	pte_t **ptes;
	unsigned long addr;
	unsigned long i;

	if (shared == gnttab_status_vm_area.area->addr)
		ptes = gnttab_status_vm_area.ptes;
	else
		ptes = gnttab_shared_vm_area.ptes;

	addr = (unsigned long)shared;

	for (i = 0; i < nr_gframes; i++) {
		set_pte_at(&init_mm, addr, ptes[i], __pte(0));
		addr += PAGE_SIZE;
	}
}

static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
{
	area->ptes = kmalloc_array(nr_frames, sizeof(*area->ptes), GFP_KERNEL);
	if (area->ptes == NULL)
		return -ENOMEM;

	area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes);
	if (area->area == NULL) {
		kfree(area->ptes);
		return -ENOMEM;
	}

	return 0;
}

static void arch_gnttab_vfree(struct gnttab_vm_area *area)
{
	free_vm_area(area->area);
	kfree(area->ptes);
}

int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
{
	int ret;

	if (!xen_pv_domain())
		return 0;

	ret = arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
	if (ret < 0)
		return ret;

	/*
	 * Always allocate the space for the status frames in case
	 * we're migrated to a host with V2 support.
	 */
	ret = arch_gnttab_valloc(&gnttab_status_vm_area, nr_status);
	if (ret < 0)
		goto err;

	return 0;
err:
	arch_gnttab_vfree(&gnttab_shared_vm_area);
	return -ENOMEM;
}

#ifdef CONFIG_XEN_PVH
#include <xen/events.h>
#include <xen/xen-ops.h>
static int __init xen_pvh_gnttab_setup(void)
{
	if (!xen_pvh_domain())
		return -ENODEV;

	xen_auto_xlat_grant_frames.count = gnttab_max_grant_frames();

	return xen_xlate_map_ballooned_pages(&xen_auto_xlat_grant_frames.pfn,
					     &xen_auto_xlat_grant_frames.vaddr,
					     xen_auto_xlat_grant_frames.count);
}
/* Call it _before_ __gnttab_init as we need to initialize the
 * xen_auto_xlat_grant_frames first. */
core_initcall(xen_pvh_gnttab_setup);
#endif