[RFC][PATCH] Hypercalls from HVM guests (2/2)

[Steve Ofsthun <sofsthun@virtualiron.com>]

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A sample test module for the HVM hypercall interface.

Signed-off-by: Steve Ofsthun <sofsthun@virtualiron.com>

1) To use, put these files in a directory by themselves.
2) Edit the Makefile:
    Set XEN_ROOT to a populated xen tree.
    Set LINUX_ROOT to a linux build tree for your HVM domU kernel.
3) make

The output should be test.ko.  You should be able to load this
module on an HVM guest using:

# insmod test.ko

Module output on the console should appear like:

hypercall_page @ ffffffffa020f000
xen_features[0].writable_page_tables = 1
xen_features[0].writable_descriptor_tables = 0
xen_features[0].auto_translated_physmap = 1
xen_features[0].supervisor_mode_kernel = 0
xen_features[0].pae_pgdir_above_4gb = 1

Enjoy,
Steve
-- 
Steve Ofsthun - Virtual Iron Software, Inc.

[-- Attachment #2: Makefile --]
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# Makefile for test driver

#EXTRA_CFLAGS += -DDEBUG

obj-m := test.o

test-objs := features.o hypercall.o

# Point XEN_ROOT at a valid xen tree

ifeq ($(XEN_ROOT),)
XEN_ROOT = ~/BK/xen-unstable-test64/
endif

# Point LINUX_ROOT at a valid linux tree

ifeq ($(LINUX_ROOT),)
LINUX_ROOT = $(XEN_ROOT)/linux-2.6.16-xen/
endif

LOCAL_DRIVER_LIST = .
LOCAL_DRIVER_DIRS := $(foreach dir,$(LOCAL_DRIVER_LIST),$(shell pwd)/$(dir))

default:
	@if [ ! -d $(XEN_ROOT) ]; then \
		echo XEN_ROOT must be set; exit 1; \
	fi
	@if [ ! -d $(LINUX_ROOT) ]; then \
		echo LINUX_ROOT must be set; exit 1; \
	fi
	$(MAKE) -C $(LINUX_ROOT) SUBDIRS="$(LOCAL_DRIVER_DIRS)" modules

clean:
	$(MAKE) -C $(LINUX_ROOT) SUBDIRS="$(LOCAL_DRIVER_DIRS)" $@

[-- Attachment #3: features.c --]
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/******************************************************************************
 * features.c
 *
 * Xen feature flags.
 *
 * Copyright (c) 2006, Ian Campbell, XenSource Inc.
 */
#include <linux/types.h>
#include <linux/cache.h>
#include <linux/module.h>
#include <asm/hypervisor.h>
#include <xen/features.h>

#ifndef __read_mostly
#define __read_mostly __cacheline_aligned
#endif

//#define DEBUG

u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
EXPORT_SYMBOL(xen_features);

#ifdef DEBUG
static const char *feature_names[XENFEAT_NR_SUBMAPS*32] = {
    [XENFEAT_writable_page_tables]       = "writable_page_tables",
    [XENFEAT_writable_descriptor_tables] = "writable_descriptor_tables",
    [XENFEAT_auto_translated_physmap]    = "auto_translated_physmap",
    [XENFEAT_supervisor_mode_kernel]     = "supervisor_mode_kernel",
    [XENFEAT_pae_pgdir_above_4gb]        = "pae_pgdir_above_4gb"
};
#endif

void setup_xen_features(void)
{
	xen_feature_info_t fi;
	int i, j;

	for (i = 0; i < XENFEAT_NR_SUBMAPS; i++) {
		fi.submap_idx = i;
		if (HYPERVISOR_xen_version(XENVER_get_features, &fi) < 0)
			break;
		for (j=0; j<32; j++)
			xen_features[i*32+j] = !!(fi.submap & 1<<j);
	}
#ifdef DEBUG
	for (i = 0; i < XENFEAT_NR_SUBMAPS; i++) {
		for (j=0; j<32; j++) {
			if (feature_names[j])
				printk("xen_features[%d].%s = %d\n", i,
					feature_names[j], xen_features[i*32+j]);
		}
	}
#endif
}
EXPORT_SYMBOL(setup_xen_features);

[-- Attachment #4: hypercall.c --]
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/******************************************************************************
 * hypercall.c
 *
 * Copyright (C) 2006, Virtual Iron Software, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 */

#include <linux/module.h>

MODULE_LICENSE("GPL");

#include "hypercall.h"

char hypercall_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));

static inline int
HYPERVISOR_arg_test(long a, long b, long c, long d, long e)
{
	return _hypercall5(int, grant_table_op, a, b, c, d, e);
}

extern void setup_xen_features(void);

static int __init hypercall_page_setup(void)
{
    hypercall_page_init(&hypercall_page);
    printk(KERN_ERR "hypercall_page @ %p\n", &hypercall_page);
#if BITS_PER_LONG == 64
    HYPERVISOR_arg_test(0x1111111111111111, 0x2222222222222222,
	0x3333333333333333, 0x4444444444444444, 0x5555555555555555);
#else
    HYPERVISOR_arg_test(0x11111111, 0x22222222,
	0x33333333, 0x44444444, 0x55555555);
#endif
    setup_xen_features();
    return 0;
}

static void __exit hypercall_page_cleanup(void)
{
}

module_init(hypercall_page_setup);
module_exit(hypercall_page_cleanup);

[-- Attachment #5: hypercall.h --]
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/******************************************************************************
 * hypercall.h
 *
 * Copyright (C) 2006, Virtual Iron Software, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 */

#include <linux/version.h>
#include <asm/hypervisor.h>
#include <xen/interface/xen.h>

static inline int
check_amd(void)
{
        char id[12];

        __asm__ __volatile__(
                "cpuid"
                : "=b" (*(int *)(&id[0])),
                  "=c" (*(int *)(&id[8])),
                  "=d" (*(int *)(&id[4]))
                : "a" (0)
        );
        return __builtin_memcmp(id, "AuthenticAMD", 12) == 0;
}

#define VMCALL_INSTR	0x0f,0x01,0xc1
#define VMMCALL_INSTR	0x0f,0x01,0xd6

#define NR_hypercalls (PAGE_SIZE/32)

static inline void hypercall_page_init(void *hypercall_page)
{
    int i;
    char *p;
    char vmcall[3] = { VMCALL_INSTR };
    char vmmcall[3] = { VMMCALL_INSTR };
    int amd = check_amd();

    for ( i = 0; i < NR_hypercalls; i++ )
    {
	p = (char *)(hypercall_page + (i * 32));
	/*
	 * This call sequence works for 32-bit and 64-bit guests.
	 */
	memset(p, 0xcc, 32);
	*(u8  *)(p+ 0) = 0xb8;		/* mov $<i>,%eax */
	*(u32 *)(p+ 1) = i;
	if (amd) {
	    *(u8  *)(p+ 5) = vmmcall[0];
	    *(u8  *)(p+ 6) = vmmcall[1];
	    *(u8  *)(p+ 7) = vmmcall[2];
	} else {
	    *(u8  *)(p+ 5) = vmcall[0];
	    *(u8  *)(p+ 6) = vmcall[1];
	    *(u8  *)(p+ 7) = vmcall[2];
	}
	*(u8  *)(p+ 8) = 0xc3;		/* ret */
    }
}

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