/* $NetBSD: acpi_vmgenid.c,v 1.3 2024/08/27 00:56:46 riastradh Exp $ */
/*-
* Copyright (c) 2024 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Virtual Machine Generation ID
*
* The VMGENID is an 8-byte cookie shared between a VM host and VM
* guest. Whenever the host clones a VM, it changes the VMGENID
* and sends an ACPI notification to the guest.
*
* References:
*
* `Virtual Machine Generation ID', Microsoft, 2012-08-01.
*
http://go.microsoft.com/fwlink/?LinkId=260709
*
* `Virtual Machine Generation ID Device', The QEMU Project
* Developers.
*
https://www.qemu.org/docs/master/specs/vmgenid.html
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: acpi_vmgenid.c,v 1.3 2024/08/27 00:56:46 riastradh Exp $");
#include <sys/device.h>
#include <sys/entropy.h>
#include <sys/module.h>
#include <sys/rndsource.h>
#include <sys/sysctl.h>
#include <dev/acpi/acpireg.h>
#include <dev/acpi/acpivar.h>
#define _COMPONENT ACPI_RESOURCE_COMPONENT
ACPI_MODULE_NAME ("acpi_vmgenid")
struct acpivmgenid {
uint8_t id[16];
} __aligned(8);
struct acpivmgenid_softc {
device_t sc_dev;
struct acpi_devnode *sc_node;
uint64_t sc_paddr;
struct acpivmgenid *sc_vaddr;
struct krndsource sc_rndsource;
struct sysctllog *sc_sysctllog;
const struct sysctlnode *sc_sysctlroot;
};
static int acpivmgenid_match(device_t, cfdata_t, void *);
static void acpivmgenid_attach(device_t, device_t, void *);
static int acpivmgenid_detach(device_t, int);
static void acpivmgenid_set(struct acpivmgenid_softc *, const char *);
static void acpivmgenid_notify(ACPI_HANDLE, uint32_t, void *);
static void acpivmgenid_reset(void *);
static int acpivmgenid_sysctl(SYSCTLFN_ARGS);
static const struct device_compatible_entry compat_data[] = {
{ .compat = "VM_Gen_Counter" }, /* from the Microsoft spec */
{ .compat = "VM_GEN_COUNTER" }, /* used by qemu */
{ .compat = "VMGENCTR" }, /* recognized by Linux */
DEVICE_COMPAT_EOL
};
CFATTACH_DECL_NEW(acpivmgenid, sizeof(struct acpivmgenid_softc),
acpivmgenid_match, acpivmgenid_attach, acpivmgenid_detach, NULL);
static int
acpivmgenid_match(device_t parent, cfdata_t match, void *aux)
{
const struct acpi_attach_args *const aa = aux;
return acpi_compatible_match(aa, compat_data);
}
static void
acpivmgenid_attach(device_t parent, device_t self, void *aux)
{
struct acpivmgenid_softc *const sc = device_private(self);
const struct acpi_attach_args *const aa = aux;
ACPI_BUFFER addrbuf = {
.Pointer = NULL,
.Length = ACPI_ALLOCATE_BUFFER,
};
ACPI_OBJECT *addrobj, *addrarr;
ACPI_STATUS rv;
int error;
aprint_naive(": ACPI VM Generation ID\n");
aprint_normal(": ACPI VM Generation ID\n");
sc->sc_dev = self;
sc->sc_node = aa->aa_node;
/*
* Get the address from the ADDR object, which is a package of
* two 32-bit integers representing the low and high halves of
* a 64-bit physical address.
*/
rv = AcpiEvaluateObjectTyped(sc->sc_node->ad_handle, "ADDR", NULL,
&addrbuf, ACPI_TYPE_PACKAGE);
if (ACPI_FAILURE(rv)) {
aprint_error_dev(self, "failed to get ADDR: %s\n",
AcpiFormatException(rv));
goto out;
}
addrobj = addrbuf.Pointer;
if (addrobj->Type != ACPI_TYPE_PACKAGE ||
addrobj->Package.Count != 2) {
aprint_error_dev(self, "invalid ADDR\n");
goto out;
}
addrarr = addrobj->Package.Elements;
if (addrarr[0].Type != ACPI_TYPE_INTEGER ||
addrarr[1].Type != ACPI_TYPE_INTEGER ||
addrarr[0].Integer.Value > UINT32_MAX ||
addrarr[1].Integer.Value > UINT32_MAX) {
aprint_error_dev(self, "invalid ADDR\n");
goto out;
}
sc->sc_paddr = (ACPI_PHYSICAL_ADDRESS)addrarr[0].Integer.Value;
sc->sc_paddr |= (ACPI_PHYSICAL_ADDRESS)addrarr[1].Integer.Value << 32;
aprint_normal_dev(self, "paddr=0x%"PRIx64"\n", (uint64_t)sc->sc_paddr);
/*
* Map the physical address into virtual address space.
*/
sc->sc_vaddr = AcpiOsMapMemory(sc->sc_paddr, sizeof(*sc->sc_vaddr));
if (sc->sc_vaddr == NULL) {
aprint_error_dev(self, "failed to map address\n");
goto out;
}
/*
* Register a random source so we can attribute samples.
*/
rnd_attach_source(&sc->sc_rndsource, device_xname(self),
RND_TYPE_UNKNOWN, RND_FLAG_COLLECT_TIME|RND_FLAG_COLLECT_VALUE);
/*
* Register an ACPI notifier so that we can detect changes.
*/
(void)acpi_register_notify(sc->sc_node, acpivmgenid_notify);
/*
* Now that we have registered a random source and a notifier,
* read out the first value.
*/
acpivmgenid_set(sc, "initial");
/*
* Attach a sysctl tree, rooted at hw.acpivmgenidN.
*/
error = sysctl_createv(&sc->sc_sysctllog, 0, NULL, &sc->sc_sysctlroot,
CTLFLAG_PERMANENT, CTLTYPE_NODE, device_xname(self),
SYSCTL_DESCR("Virtual Machine Generation ID device"),
NULL, 0, NULL, 0,
CTL_HW, CTL_CREATE, CTL_EOL);
if (error) {
aprint_error_dev(self, "failed to create sysctl hw.%s: %d\n",
device_xname(self), error);
goto out;
}
/*
* hw.acpivmgenidN.id (`struct', 16-byte array)
*/
error = sysctl_createv(&sc->sc_sysctllog, 0, &sc->sc_sysctlroot, NULL,
CTLFLAG_PERMANENT|CTLFLAG_READONLY|CTLFLAG_PRIVATE, CTLTYPE_STRUCT,
"id", SYSCTL_DESCR("Virtual Machine Generation ID"),
&acpivmgenid_sysctl, 0, sc, sizeof(struct acpivmgenid),
CTL_CREATE, CTL_EOL);
if (error) {
aprint_error_dev(self,
"failed to create sysctl hw.%s.id: %d\n",
device_xname(self), error);
goto out;
}
/*
* hw.acpivmgenidN.paddr (64-bit integer)
*/
__CTASSERT(sizeof(ACPI_PHYSICAL_ADDRESS) == sizeof(quad_t));
error = sysctl_createv(&sc->sc_sysctllog, 0, &sc->sc_sysctlroot, NULL,
CTLFLAG_PERMANENT|CTLFLAG_READONLY|CTLFLAG_PRIVATE, CTLTYPE_QUAD,
"paddr", SYSCTL_DESCR("Physical address of VM Generation ID"),
NULL, 0, &sc->sc_paddr, sizeof(sc->sc_paddr),
CTL_CREATE, CTL_EOL);
if (error) {
aprint_error_dev(self,
"failed to create sysctl hw.%s.paddr: %d\n",
device_xname(self), error);
goto out;
}
out: ACPI_FREE(addrbuf.Pointer);
}
static int
acpivmgenid_detach(device_t self, int flags)
{
struct acpivmgenid_softc *const sc = device_private(self);
int error;
error = config_detach_children(self, flags);
if (error)
return error;
sysctl_teardown(&sc->sc_sysctllog);
acpi_deregister_notify(sc->sc_node);
rnd_detach_source(&sc->sc_rndsource);
if (sc->sc_vaddr) {
AcpiOsUnmapMemory(sc->sc_vaddr, sizeof(*sc->sc_vaddr));
sc->sc_vaddr = NULL; /* paranoia */
}
sc->sc_paddr = 0; /* paranoia */
return 0;
}
static void
acpivmgenid_set(struct acpivmgenid_softc *sc, const char *prefix)
{
struct acpivmgenid vmgenid;
char vmgenidstr[2*__arraycount(vmgenid.id) + 1];
unsigned i;
/*
* Grab the current VM generation ID. No obvious way to make
* this atomic, so let's hope if it changes in the middle we'll
* get another notification.
*/
memcpy(&vmgenid, sc->sc_vaddr, sizeof(vmgenid));
/*
* Print the VM generation ID to the console for posterity.
*/
for (i = 0; i < __arraycount(vmgenid.id); i++) {
vmgenidstr[2*i] = "0123456789abcdef"[vmgenid.id[i] >> 4];
vmgenidstr[2*i + 1] = "0123456789abcdef"[vmgenid.id[i] & 0xf];
}
vmgenidstr[2*sizeof(vmgenid)] = '\0';
aprint_verbose_dev(sc->sc_dev, "%s: %s\n", prefix, vmgenidstr);
/*
* Enter the new VM generation ID into the entropy pool.
*/
rnd_add_data(&sc->sc_rndsource, &vmgenid, sizeof(vmgenid), 0);
}
static void
acpivmgenid_notify(ACPI_HANDLE hdl, uint32_t notify, void *opaque)
{
const device_t self = opaque;
struct acpivmgenid_softc *const sc = device_private(self);
if (notify != 0x80) {
aprint_debug_dev(self, "unknown notify 0x%02x\n", notify);
return;
}
(void)AcpiOsExecute(OSL_NOTIFY_HANDLER, &acpivmgenid_reset, sc);
}
static void
acpivmgenid_reset(void *cookie)
{
struct acpivmgenid_softc *const sc = cookie;
/*
* Reset the system entropy pool's measure of entropy (not the
* data, just the system's assessment of whether it has
* entropy), and gather more entropy from any synchronous
* sources we have available like CPU RNG instructions. We
* can't be interrupted by a signal so ignore return value.
*/
entropy_reset();
(void)entropy_gather();
/*
* Grab the current VM generation ID to put it into the entropy
* pool; then force consolidation so it affects all subsequent
* draws from the entropy pool and the entropy epoch advances.
* Again we can't be interrupted by a signal so ignore return
* value.
*/
acpivmgenid_set(sc, "cloned");
(void)entropy_consolidate();
}
static int
acpivmgenid_sysctl(SYSCTLFN_ARGS)
{
struct sysctlnode node = *rnode;
struct acpivmgenid_softc *const sc = node.sysctl_data;
node.sysctl_data = sc->sc_vaddr;
return sysctl_lookup(SYSCTLFN_CALL(&node));
}
MODULE(MODULE_CLASS_DRIVER, acpivmgenid, NULL);
#ifdef _MODULE
#include "ioconf.c"
#endif
static int
acpivmgenid_modcmd(modcmd_t cmd, void *opaque)
{
int error = 0;
switch (cmd) {
case MODULE_CMD_INIT:
#ifdef _MODULE
error = config_init_component(cfdriver_ioconf_acpivmgenid,
cfattach_ioconf_acpivmgenid, cfdata_ioconf_acpivmgenid);
#endif
return error;
case MODULE_CMD_FINI:
#ifdef _MODULE
error = config_fini_component(cfdriver_ioconf_acpivmgenid,
cfattach_ioconf_acpivmgenid, cfdata_ioconf_acpivmgenid);
#endif
return error;
default:
return ENOTTY;
}
}
