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Merge pull request #19403 from nmeyerhans/dmi-entries

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virt: differentiate Amazon EC2 bare-metal from VM instances using SMBIOS data
This commit is contained in:
Lennart Poettering 2021-05-03 17:48:13 +02:00 committed by GitHub
commit 16ecdf3c80
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6 changed files with 83 additions and 14 deletions
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7
man/systemd-detect-virt.xml
View File

@ -69,7 +69,12 @@
<row>
<entry><varname>kvm</varname></entry>
<entry>Linux KVM kernel virtual machine, with whatever software, except Oracle Virtualbox</entry>
<entry>Linux KVM kernel virtual machine, in combination with QEMU. Not used for other virtualizers using the KVM interfaces, such as Oracle VirtualBox or Amazon EC2 Nitro, see below.</entry>
</row>
<row>
<entry><varname>amazon</varname></entry>
<entry>Amazon EC2 Nitro using Linux KVM</entry>
</row>
<row>

1
man/systemd.unit.xml
View File

@ -1192,6 +1192,7 @@
<literal>container</literal> to test against a generic type of virtualization solution, or one of
<literal>qemu</literal>,
<literal>kvm</literal>,
<literal>amazon</literal>,
<literal>zvm</literal>,
<literal>vmware</literal>,
<literal>microsoft</literal>,

78
src/basic/virt.c
View File

@ -21,6 +21,12 @@
#include "string-util.h"
#include "virt.h"
enum {
SMBIOS_VM_BIT_SET,
SMBIOS_VM_BIT_UNSET,
SMBIOS_VM_BIT_UNKNOWN,
};
#if defined(__i386__) || defined(__x86_64__)
static const char *const vm_table[_VIRTUALIZATION_MAX] = {
[VIRTUALIZATION_XEN] = "XenVMMXenVMM",
@ -134,9 +140,8 @@ static int detect_vm_device_tree(void) {
#endif
}
static int detect_vm_dmi(void) {
#if defined(__i386__) || defined(__x86_64__) || defined(__arm__) || defined(__aarch64__)
static int detect_vm_dmi_vendor(void) {
static const char *const dmi_vendors[] = {
"/sys/class/dmi/id/product_name", /* Test this before sys_vendor to detect KVM over QEMU */
"/sys/class/dmi/id/sys_vendor",
@ -149,6 +154,7 @@ static int detect_vm_dmi(void) {
int id;
} dmi_vendor_table[] = {
{ "KVM", VIRTUALIZATION_KVM },
{ "Amazon EC2", VIRTUALIZATION_AMAZON },
{ "QEMU", VIRTUALIZATION_QEMU },
{ "VMware", VIRTUALIZATION_VMWARE }, /* https://kb.vmware.com/s/article/1009458 */
{ "VMW", VIRTUALIZATION_VMWARE },
@ -180,13 +186,65 @@ static int detect_vm_dmi(void) {
return dmi_vendor_table[j].id;
}
}
#endif
log_debug("No virtualization found in DMI");
return VIRTUALIZATION_NONE;
}
static int detect_vm_smbios(void) {
/* The SMBIOS BIOS Charateristics Extension Byte 2 (Section 2.1.2.2 of
* https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.4.0.pdf), specifies that
* the 4th bit being set indicates a VM. The BIOS Characteristics table is exposed via the kernel in
* /sys/firmware/dmi/entries/0-0. Note that in the general case, this bit being unset should not
* imply that the system is running on bare-metal. For example, QEMU 3.1.0 (with or without KVM)
* with SeaBIOS does not set this bit. */
_cleanup_free_ char *s = NULL;
size_t readsize;
int r;
r = read_full_virtual_file("/sys/firmware/dmi/entries/0-0/raw", &s, &readsize);
if (r < 0) {
log_debug_errno(r, "Unable to read /sys/firmware/dmi/entries/0-0/raw, ignoring: %m");
return SMBIOS_VM_BIT_UNKNOWN;
}
if (readsize < 20 || s[1] < 20) {
/* The spec indicates that byte 1 contains the size of the table, 0x12 + the number of
* extension bytes. The data we're interested in is in extension byte 2, which would be at
* 0x13. If we didn't read that much data, or if the BIOS indicates that we don't have that
* much data, we don't infer anything from the SMBIOS. */
log_debug("Only read %zu bytes from /sys/firmware/dmi/entries/0-0/raw (expected 20)", readsize);
return SMBIOS_VM_BIT_UNKNOWN;
}
uint8_t byte = (uint8_t) s[19];
if (byte & (1U<<4)) {
log_debug("DMI BIOS Extension table indicates virtualization");
return SMBIOS_VM_BIT_SET;
}
log_debug("DMI BIOS Extension table does not indicate virtualization");
return SMBIOS_VM_BIT_UNSET;
}
#endif /* defined(__i386__) || defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) */
static int detect_vm_dmi(void) {
#if defined(__i386__) || defined(__x86_64__) || defined(__arm__) || defined(__aarch64__)
int r;
r = detect_vm_dmi_vendor();
/* The DMI vendor tables in /sys/class/dmi/id don't help us distinguish between Amazon EC2
* virtual machines and bare-metal instances, so we need to look at SMBIOS. */
if (r == VIRTUALIZATION_AMAZON && detect_vm_smbios() == SMBIOS_VM_BIT_UNSET)
return VIRTUALIZATION_NONE;
/* If we haven't identified a VM, but the firmware indicates that there is one, indicate as much. We
* have no further information about what it is. */
if (r == VIRTUALIZATION_NONE && detect_vm_smbios() == SMBIOS_VM_BIT_SET)
return VIRTUALIZATION_VM_OTHER;
return r;
#else
return VIRTUALIZATION_NONE;
#endif
}
static int detect_vm_xen(void) {
/* Check for Dom0 will be executed later in detect_vm_xen_dom0
@ -344,8 +402,9 @@ int detect_vm(void) {
/* We have to use the correct order here:
*
* → First, try to detect Oracle Virtualbox, even if it uses KVM, as well as Xen even if it cloaks as Microsoft
* Hyper-V. Attempt to detect uml at this stage also since it runs as a user-process nested inside other VMs.
* → First, try to detect Oracle Virtualbox and Amazon EC2 Nitro, even if they use KVM, as well as Xen even if
* it cloaks as Microsoft Hyper-V. Attempt to detect uml at this stage also since it runs as a user-process
* nested inside other VMs.
*
* → Second, try to detect from CPUID, this will report KVM for whatever software is used even if info in DMI is
* overwritten.
@ -353,7 +412,7 @@ int detect_vm(void) {
* → Third, try to detect from DMI. */
dmi = detect_vm_dmi();
if (IN_SET(dmi, VIRTUALIZATION_ORACLE, VIRTUALIZATION_XEN)) {
if (IN_SET(dmi, VIRTUALIZATION_ORACLE, VIRTUALIZATION_XEN, VIRTUALIZATION_AMAZON)) {
r = dmi;
goto finish;
}
@ -914,6 +973,7 @@ bool has_cpu_with_flag(const char *flag) {
static const char *const virtualization_table[_VIRTUALIZATION_MAX] = {
[VIRTUALIZATION_NONE] = "none",
[VIRTUALIZATION_KVM] = "kvm",
[VIRTUALIZATION_AMAZON] = "amazon",
[VIRTUALIZATION_QEMU] = "qemu",
[VIRTUALIZATION_BOCHS] = "bochs",
[VIRTUALIZATION_XEN] = "xen",

1
src/basic/virt.h
View File

@ -10,6 +10,7 @@ enum {
VIRTUALIZATION_VM_FIRST,
VIRTUALIZATION_KVM = VIRTUALIZATION_VM_FIRST,
VIRTUALIZATION_AMAZON,
VIRTUALIZATION_QEMU,
VIRTUALIZATION_BOCHS,
VIRTUALIZATION_XEN,

9
src/shared/machine-id-setup.c
View File

@ -60,13 +60,14 @@ static int generate_machine_id(const char *root, sd_id128_t *ret) {
return 0;
}
} else if (detect_vm() == VIRTUALIZATION_KVM) {
} else if (IN_SET(detect_vm(), VIRTUALIZATION_KVM, VIRTUALIZATION_AMAZON, VIRTUALIZATION_QEMU)) {
/* If we are not running in a container, see if we are running in qemu/kvm and a
* machine ID was passed in via -uuid on the qemu/kvm command line */
/* If we are not running in a container, see if we are running in a VM that provides
* a system UUID via the SMBIOS/DMI interfaces. Such environments include QEMU/KVM
* with the -uuid on the qemu command line or the Amazon EC2 Nitro hypervisor. */
if (id128_get_product(ret) >= 0) {
log_info("Initializing machine ID from KVM UUID.");
log_info("Initializing machine ID from VM UUID.");
return 0;
}
}

1
src/test/test-condition.c
View File

@ -575,6 +575,7 @@ static void test_condition_test_virtualization(void) {
NULSTR_FOREACH(virt,
"kvm\0"
"amazon\0"
"qemu\0"
"bochs\0"
"xen\0"