Commit b2371587 authored by Oleksandr Tyshchenko's avatar Oleksandr Tyshchenko Committed by Juergen Gross
Browse files

arm/xen: Read extended regions from DT and init Xen resource 



This patch implements arch_xen_unpopulated_init() on Arm where
the extended regions (if any) are gathered from DT and inserted
into specific Xen resource to be used as unused address space
for Xen scratch pages by unpopulated-alloc code.

The extended region (safe range) is a region of guest physical
address space which is unused and could be safely used to create
grant/foreign mappings instead of wasting real RAM pages from
the domain memory for establishing these mappings.

The extended regions are chosen by the hypervisor at the domain
creation time and advertised to it via "reg" property under
hypervisor node in the guest device-tree. As region 0 is reserved
for grant table space (always present), the indexes for extended
regions are 1...N.

If arch_xen_unpopulated_init() fails for some reason the default
behaviour will be restored (allocate xenballooned pages).

This patch also removes XEN_UNPOPULATED_ALLOC dependency on x86.

Signed-off-by: default avatarOleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: default avatarStefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1639080336-26573-6-git-send-email-olekstysh@gmail.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent d1a928ea

arch/arm/xen/enlighten.c

+106 −0
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ static __read_mostly unsigned int xen_events_irq; 
static __read_mostly phys_addr_t xen_grant_frames;



#define GRANT_TABLE_INDEX   0

#define EXT_REGION_INDEX    1



uint32_t xen_start_flags;

EXPORT_SYMBOL(xen_start_flags);
@@ -303,6 +304,111 @@ static void __init xen_acpi_guest_init(void) 
#endif

}



#ifdef CONFIG_XEN_UNPOPULATED_ALLOC

/*

 * A type-less specific Xen resource which contains extended regions

 * (unused regions of guest physical address space provided by the hypervisor).

 */

static struct resource xen_resource = {

	.name = "Xen unused space",

};



int __init arch_xen_unpopulated_init(struct resource **res)

{

	struct device_node *np;

	struct resource *regs, *tmp_res;

	uint64_t min_gpaddr = -1, max_gpaddr = 0;

	unsigned int i, nr_reg = 0;

	int rc;



	if (!xen_domain())

		return -ENODEV;



	if (!acpi_disabled)

		return -ENODEV;



	np = of_find_compatible_node(NULL, NULL, "xen,xen");

	if (WARN_ON(!np))

		return -ENODEV;



	/* Skip region 0 which is reserved for grant table space */

	while (of_get_address(np, nr_reg + EXT_REGION_INDEX, NULL, NULL))

		nr_reg++;



	if (!nr_reg) {

		pr_err("No extended regions are found\n");

		return -EINVAL;

	}



	regs = kcalloc(nr_reg, sizeof(*regs), GFP_KERNEL);

	if (!regs)

		return -ENOMEM;



	/*

	 * Create resource from extended regions provided by the hypervisor to be

	 * used as unused address space for Xen scratch pages.

	 */

	for (i = 0; i < nr_reg; i++) {

		rc = of_address_to_resource(np, i + EXT_REGION_INDEX, &regs[i]);

		if (rc)

			goto err;



		if (max_gpaddr < regs[i].end)

			max_gpaddr = regs[i].end;

		if (min_gpaddr > regs[i].start)

			min_gpaddr = regs[i].start;

	}



	xen_resource.start = min_gpaddr;

	xen_resource.end = max_gpaddr;



	/*

	 * Mark holes between extended regions as unavailable. The rest of that

	 * address space will be available for the allocation.

	 */

	for (i = 1; i < nr_reg; i++) {

		resource_size_t start, end;



		/* There is an overlap between regions */

		if (regs[i - 1].end + 1 > regs[i].start) {

			rc = -EINVAL;

			goto err;

		}



		/* There is no hole between regions */

		if (regs[i - 1].end + 1 == regs[i].start)

			continue;



		start = regs[i - 1].end + 1;

		end = regs[i].start - 1;



		tmp_res = kzalloc(sizeof(*tmp_res), GFP_KERNEL);

		if (!tmp_res) {

			rc = -ENOMEM;

			goto err;

		}



		tmp_res->name = "Unavailable space";

		tmp_res->start = start;

		tmp_res->end = end;



		rc = insert_resource(&xen_resource, tmp_res);

		if (rc) {

			pr_err("Cannot insert resource %pR (%d)\n", tmp_res, rc);

			kfree(tmp_res);

			goto err;

		}

	}



	*res = &xen_resource;



err:

	kfree(regs);



	return rc;

}

#endif



static void __init xen_dt_guest_init(void)

{

	struct device_node *xen_node;

drivers/xen/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -327,7 +327,7 @@ config XEN_FRONT_PGDIR_SHBUF 


config XEN_UNPOPULATED_ALLOC

	bool "Use unpopulated memory ranges for guest mappings"

	depends on X86 && ZONE_DEVICE

	depends on ZONE_DEVICE

	default XEN_BACKEND || XEN_GNTDEV || XEN_DOM0

	help

	  Use unpopulated memory ranges in order to create mappings for guest