[PATCH 11/17] xen: Port Xen grant table driver from mini-os

[Julien Grall <julien@xen.org>]

On 01/07/2020 17:29, Anastasiia Lukianenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> 
> Make required updates to run on u-boot.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
> ---
>   board/xen/xenguest_arm64/xenguest_arm64.c |  13 ++
>   drivers/xen/Makefile                      |   1 +
>   drivers/xen/gnttab.c                      | 258 ++++++++++++++++++++++
>   drivers/xen/hypervisor.c                  |   2 +
>   include/xen/gnttab.h                      |  25 +++
>   5 files changed, 299 insertions(+)
>   create mode 100644 drivers/xen/gnttab.c
>   create mode 100644 include/xen/gnttab.h
> 
> diff --git a/board/xen/xenguest_arm64/xenguest_arm64.c b/board/xen/xenguest_arm64/xenguest_arm64.c
> index e8621f7174..b4e1650f99 100644
> --- a/board/xen/xenguest_arm64/xenguest_arm64.c
> +++ b/board/xen/xenguest_arm64/xenguest_arm64.c
> @@ -22,6 +22,7 @@
>   
>   #include <linux/compiler.h>
>   
> +#include <xen/gnttab.h>
>   #include <xen/hvm.h>
>   
>   DECLARE_GLOBAL_DATA_PTR;
> @@ -64,6 +65,8 @@ static int setup_mem_map(void)
>   	struct fdt_resource res;
>   	const void *blob = gd->fdt_blob;
>   	u64 gfn;
> +	phys_addr_t gnttab_base;
> +	phys_size_t gnttab_sz;
>   
>   	/*
>   	 * Add "magic" region which is used by Xen to provide some essentials
> @@ -97,6 +100,16 @@ static int setup_mem_map(void)
>   				PTE_BLOCK_INNER_SHARE);
>   	i++;
>   
> +	/* Get Xen's suggested physical page assignments for the grant table. */
> +	get_gnttab_base(&gnttab_base, &gnttab_sz);
> +
> +	xen_mem_map[i].virt = gnttab_base;
> +	xen_mem_map[i].phys = gnttab_base;
> +	xen_mem_map[i].size = gnttab_sz;
> +	xen_mem_map[i].attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> +				PTE_BLOCK_INNER_SHARE);
> +	i++;
> +
>   	mem = get_next_memory_node(blob, -1);
>   	if (mem < 0) {
>   		printf("%s: Missing /memory node\n", __func__);
> diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> index 9d0f604aaa..243b13277a 100644
> --- a/drivers/xen/Makefile
> +++ b/drivers/xen/Makefile
> @@ -5,3 +5,4 @@
>   obj-y += hypervisor.o
>   obj-y += events.o
>   obj-y += xenbus.o
> +obj-y += gnttab.o
> diff --git a/drivers/xen/gnttab.c b/drivers/xen/gnttab.c
> new file mode 100644
> index 0000000000..b18102e329
> --- /dev/null
> +++ b/drivers/xen/gnttab.c
> @@ -0,0 +1,258 @@
> +/*
> + ****************************************************************************
> + * (C) 2006 - Cambridge University
> + * (C) 2020 - EPAM Systems Inc.
> + ****************************************************************************
> + *
> + *		File: gnttab.c
> + *	  Author: Steven Smith (sos22 at cam.ac.uk)
> + *	 Changes: Grzegorz Milos (gm281 at cam.ac.uk)
> + *
> + *		Date: July 2006
> + *
> + * Environment: Xen Minimal OS
> + * Description: Simple grant tables implementation. About as stupid as it's
> + *  possible to be and still work.
> + *
> + ****************************************************************************
> + */
> +#include <common.h>
> +#include <linux/compiler.h>
> +#include <log.h>
> +#include <malloc.h>
> +
> +#include <asm/armv8/mmu.h>
> +#include <asm/io.h>
> +#include <asm/xen/system.h>
> +
> +#include <linux/bug.h>
> +
> +#include <xen/gnttab.h>
> +#include <xen/hvm.h>
> +
> +#include <xen/interface/memory.h>
> +
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +#define NR_RESERVED_ENTRIES 8
> +
> +/* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
> +#define NR_GRANT_FRAMES 1
> +#define NR_GRANT_ENTRIES (NR_GRANT_FRAMES * PAGE_SIZE / sizeof(struct grant_entry_v1))
> +
> +static struct grant_entry_v1 *gnttab_table;
> +static grant_ref_t gnttab_list[NR_GRANT_ENTRIES];
> +
> +static void put_free_entry(grant_ref_t ref)
> +{
> +	unsigned long flags;
> +
> +	local_irq_save(flags);
> +	gnttab_list[ref] = gnttab_list[0];
> +	gnttab_list[0]  = ref;
> +	local_irq_restore(flags);
> +}
> +
> +static grant_ref_t get_free_entry(void)
> +{
> +	unsigned int ref;
> +	unsigned long flags;
> +
> +	local_irq_save(flags);
> +	ref = gnttab_list[0];
> +	BUG_ON(ref < NR_RESERVED_ENTRIES || ref >= NR_GRANT_ENTRIES);
> +	gnttab_list[0] = gnttab_list[ref];
> +	local_irq_restore(flags);
> +	return ref;
> +}
> +
> +grant_ref_t gnttab_grant_access(domid_t domid, unsigned long frame, int readonly)
> +{
> +	grant_ref_t ref;
> +
> +	ref = get_free_entry();
> +	gnttab_table[ref].frame = frame;
> +	gnttab_table[ref].domid = domid;
> +	wmb();
> +	readonly *= GTF_readonly;
> +	gnttab_table[ref].flags = GTF_permit_access | readonly;
> +
> +	return ref;
> +}
> +
> +grant_ref_t gnttab_grant_transfer(domid_t domid, unsigned long pfn)

It is not possible to transfer grant on Arm. So I would suggest to 
remove the code related to it.

[...]

> +unsigned long gnttab_end_transfer(grant_ref_t ref)

likewise.

> +{
> +	unsigned long frame;
> +	u16 flags;
> +
> +	BUG_ON(ref >= NR_GRANT_ENTRIES || ref < NR_RESERVED_ENTRIES);
> +
> +	while (!((flags = gnttab_table[ref].flags) & GTF_transfer_committed)) {
> +		if (synch_cmpxchg(&gnttab_table[ref].flags, flags, 0) == flags) {
> +			printf("Release unused transfer grant.\n");
> +			put_free_entry(ref);
> +			return 0;
> +		}
> +	}
> +
> +	/* If a transfer is in progress then wait until it is completed. */
> +	while (!(flags & GTF_transfer_completed))
> +		flags = gnttab_table[ref].flags;
> +
> +	/* Read the frame number /after/ reading completion status. */
> +	rmb();
> +	frame = gnttab_table[ref].frame;
> +
> +	put_free_entry(ref);
> +
> +	return frame;
> +}
> +
> +grant_ref_t gnttab_alloc_and_grant(void **map)
> +{
> +	unsigned long mfn;
> +	grant_ref_t gref;
> +
> +	*map = (void *)memalign(PAGE_SIZE, PAGE_SIZE);
> +	mfn = virt_to_mfn(*map);
> +	gref = gnttab_grant_access(0, mfn, 0);
> +	return gref;
> +}
> +
> +static const char * const gnttabop_error_msgs[] = GNTTABOP_error_msgs;
> +
> +const char *gnttabop_error(int16_t status)
> +{
> +	status = -status;
> +	if (status < 0 || status >= ARRAY_SIZE(gnttabop_error_msgs))
> +		return "bad status";
> +	else
> +		return gnttabop_error_msgs[status];
> +}
> +
> +/* Get Xen's suggested physical page assignments for the grant table. */
> +void get_gnttab_base(phys_addr_t *gnttab_base, phys_size_t *gnttab_sz)
> +{
> +	const void *blob = gd->fdt_blob;
> +	struct fdt_resource res;
> +	int mem;
> +
> +	mem = fdt_node_offset_by_compatible(blob, -1, "xen,xen");
> +	if (mem < 0) {
> +		printf("No xen,xen compatible found\n");
> +		BUG();
> +	}
> +
> +	mem = fdt_get_resource(blob, mem, "reg", 0, &res);
> +	if (mem == -FDT_ERR_NOTFOUND) {
> +		printf("No grant table base in the device tree\n");
> +		BUG();
> +	}
> +
> +	*gnttab_base = (phys_addr_t)res.start;
> +	if (gnttab_sz)
> +		*gnttab_sz = (phys_size_t)(res.end - res.start + 1);
> +
> +	debug("FDT suggests grant table base at %llx\n",
> +	      *gnttab_base);
> +}
> +
> +void init_gnttab(void)
> +{
> +	struct xen_add_to_physmap xatp;
> +	struct gnttab_setup_table setup;
> +	xen_pfn_t frames[NR_GRANT_FRAMES];
> +	int i, rc;
> +
> +	debug("%s\n", __func__);
> +
> +	for (i = NR_RESERVED_ENTRIES; i < NR_GRANT_ENTRIES; i++)
> +		put_free_entry(i);
> +
> +	get_gnttab_base((phys_addr_t *)&gnttab_table, NULL);
> +
> +	for (i = 0; i < NR_GRANT_FRAMES; i++) {
> +		xatp.domid = DOMID_SELF;
> +		xatp.size = 0;
> +		xatp.space = XENMAPSPACE_grant_table;
> +		xatp.idx = i;
> +		xatp.gpfn = PFN_DOWN((unsigned long)gnttab_table) + i;
> +		rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
> +		if (rc)
> +			printf("XENMEM_add_to_physmap failed; status = %d\n",
> +			       rc);
> +		BUG_ON(rc != 0);
> +	}
> +
> +	setup.dom = DOMID_SELF;
> +	setup.nr_frames = NR_GRANT_FRAMES;
> +	set_xen_guest_handle(setup.frame_list, frames);
> +	rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
> +	if (rc || setup.status) {
> +		printf("GNTTABOP_setup_table failed; status = %s\n",
> +		       gnttabop_error(setup.status));
> +		BUG();
> +	}

GNTTAOP_grant_table_op is not needed on Arm.

> +}
> +
> +void fini_gnttab(void)
> +{
> +	struct xen_remove_from_physmap xrtp;
> +	struct gnttab_setup_table setup;
> +	int i, rc;
> +
> +	debug("%s\n", __func__);
> +
> +	for (i = 0; i < NR_GRANT_FRAMES; i++) {
> +		xrtp.domid = DOMID_SELF;
> +		xrtp.gpfn = PFN_DOWN((unsigned long)gnttab_table) + i;
> +		rc = HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrtp);
> +		if (rc)
> +			printf("XENMEM_remove_from_physmap failed; status = %d\n",
> +			       rc);
> +		BUG_ON(rc != 0);
> +	}
> +
> +	setup.dom = DOMID_SELF;
> +	setup.nr_frames = 0;
> +
> +	HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
> +	if (setup.status) {
> +		printf("GNTTABOP_setup_table failed; status = %s\n",
> +		       gnttabop_error(setup.status));
> +		BUG();
> +	}

The hypercall doesn't do any clean-up in Xen. So why are you calling 
this from fini_gnttab()?

Cheers,

-- 
Julien Grall