TSEG (Top of Memory Segment) is one of many regions that SMM (System Management
Mode) can occupy. This one, however is special, because a) most of the SMM code
lives in TSEG nowadays and b) QEMU just (well, some time ago) added support for
so called 'extended' TSEG. The difference to the TSEG implemented in real q35's
MCH (Memory Controller Hub) is that it can have any size from 1 MiB up to 65534
MiB in 1 MiB increments. But more about that in the QEMU patch.
Signed-off-by: Martin Kletzander <mklet...@redhat.com>
---
docs/formatdomain.html.in | 39 +++++++++++++++++++
docs/schemas/domaincommon.rng | 5 +++
src/conf/domain_conf.c | 60 ++++++++++++++++++++++++++++-
src/conf/domain_conf.h | 1 +
tests/genericxml2xmlindata/tseg.xml | 23 +++++++++++
tests/genericxml2xmltest.c | 2 +
6 files changed, 129 insertions(+), 1 deletion(-)
create mode 100644 tests/genericxml2xmlindata/tseg.xml
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 403b638bd4bd..39ebfe398bd7 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -1897,6 +1897,9 @@
<ioapic driver='qemu'/>
<hpt resizing='required'/>
<vmcoreinfo state='on'/>
+ <smm state='on'>
+ <tseg unit='MiB'>48</tseg>
+ </smm>
</features>
...</pre>
@@ -2056,6 +2059,42 @@
<code>off</code>, default <code>on</code>) enable or disable
System Management Mode.
<span class="since">Since 2.1.0</span>
+
+ Optional sub-element <code>tseg</code> can be used to specify the
+ amount of memory dedicated to SMM TSEG. The size can be specified as
a
+ value of that element, optional attribute <code>unit</code> can be
+ used to specify the unit of the aforementioned value (defaults to
+ 'MiB').
+
+ This value is configurable due to the fact that the calculation
cannot
+ be done right with the guarantee that it will work correctly. For
+ QEMU TSEG was disabled up to and including <code>pc-q35-2.9</code>
(it
+ does not make sense fo any other machine type than q35).
+ From <code>pc-q35-2.10</code> the default value was changed to 16
MiB.
+ That should suffice for up to 272 VCPUs, 5 GiB guest RAM in total, no
+ hotplug memory range, and 32 GiB of 64-bit PCI MMIO aperture. Or for
+ 48 VCPUs, with 1TB of guest RAM, no hotplug DIMM range, and 32GB of
+ 64-bit PCI MMIO aperture. The values may also vary based on the
loader
+ the VM is using.
+
+ Additional size might be needed for significantly higher VCPU counts
+ or increased address space (that can be memory, maxMemory, 64-bit PCI
+ MMIO aperture size; roughly 8 MiB of TSEG per 1 TiB of address space)
+ which can also be rounded up.
+
+ Due to the nature of this setting being similar to "how much RAM
+ should the guest have" users are advised to either consult the
+ documentation of the guest OS or loader (if there is any), or test
+ this by trial-and-error changing the value until the VM boots
+ successfully. Yet another guiding value for users might be the fact
+ that 48 MiB should be enough for pretty large guests (240 VCPUs and
+ 4TB guest RAM), but it is on purpose not set as default as 48 MiB of
+ unavailable RAM might be too much for small guests (e.g. with 512 MiB
+ of RAM).
+
+ See <a href="#elementsMemoryAllocation">Memory Allocation</a>
+ for more details about the <code>unit</code> attribute.
+ <span class="since">Since 4.5.0</span> (QEMU only)
</dd>
<dt><code>ioapic</code></dt>
<dd>Tune the I/O APIC. Possible values for the
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 71ac3d079c32..664ec79933f0 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -4785,6 +4785,11 @@
<ref name="virOnOff"/>
</attribute>
</optional>
+ <optional>
+ <element name="tseg">
+ <ref name="scaledInteger"/>
+ </element>
+ </optional>
</element>
</optional>
<optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 3689ac0a82ce..6a4f8243183d 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -19647,6 +19647,16 @@ virDomainDefParseXML(xmlDocPtr xml,
VIR_FREE(nodes);
}
+ if (def->features[VIR_DOMAIN_FEATURE_SMM] == VIR_TRISTATE_SWITCH_ON &&
+ virDomainParseScaledValue("string(./features/smm/tseg)",
+ "string(./features/smm/tseg/@unit)",
+ ctxt,
+ &def->tseg_size,
+ 1024 * 1024, /* Defaults to mebibytes */
+ ULLONG_MAX,
+ false) < 0)
+ goto error;
+
if ((n = virXPathNodeSet("./features/capabilities/*", ctxt, &nodes)) < 0)
goto error;
@@ -21741,6 +21751,23 @@ virDomainDefFeaturesCheckABIStability(virDomainDefPtr
src,
}
}
+ /* smm */
+ if (src->features[VIR_DOMAIN_FEATURE_SMM] == VIR_TRISTATE_SWITCH_ON &&
+ src->tseg_size != dst->tseg_size) {
+ const char *unit_src, *unit_dst;
+ unsigned long long short_size_src = virFormatIntPretty(src->tseg_size,
+ &unit_src);
+ unsigned long long short_size_dst = virFormatIntPretty(dst->tseg_size,
+ &unit_dst);
+
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+ _("Size of SMM TSEG size differs: "
+ "source: '%llu %s', destination: '%llu %s'"),
+ short_size_src, unit_src,
+ short_size_dst, unit_dst);
+ return false;
+ }
+
return true;
}
@@ -27059,7 +27086,6 @@ virDomainDefFormatInternal(virDomainDefPtr def,
case VIR_DOMAIN_FEATURE_PMU:
case VIR_DOMAIN_FEATURE_PVSPINLOCK:
case VIR_DOMAIN_FEATURE_VMPORT:
- case VIR_DOMAIN_FEATURE_SMM:
switch ((virTristateSwitch) def->features[i]) {
case VIR_TRISTATE_SWITCH_LAST:
case VIR_TRISTATE_SWITCH_ABSENT:
@@ -27076,6 +27102,38 @@ virDomainDefFormatInternal(virDomainDefPtr def,
break;
+ case VIR_DOMAIN_FEATURE_SMM:
+ switch ((virTristateSwitch) def->features[i]) {
+ case VIR_TRISTATE_SWITCH_LAST:
+ case VIR_TRISTATE_SWITCH_ABSENT:
+ break;
+
+ case VIR_TRISTATE_SWITCH_ON:
+ virBufferAddLit(buf, "<smm state='on'");
+ if (!def->tseg_size) {
+ virBufferAddLit(buf, "/>\n");
+ } else {
+ const char *unit;
+ unsigned long long short_size =
virFormatIntPretty(def->tseg_size,
+
&unit);
+
+ virBufferAddLit(buf, ">\n");
+ virBufferAdjustIndent(buf, 2);
+ virBufferAsprintf(buf, "<tseg unit='%s'>%llu</tseg>\n",
+ unit, short_size);
+ virBufferAdjustIndent(buf, -2);
+ virBufferAddLit(buf, "</smm>\n");
+ }
+
+ break;
+
+ case VIR_TRISTATE_SWITCH_OFF:
+ virBufferAddLit(buf, "<smm state='off'/>\n");
+ break;
+ }
+
+ break;
+
case VIR_DOMAIN_FEATURE_APIC:
if (def->features[i] == VIR_TRISTATE_SWITCH_ON) {
virBufferAddLit(buf, "<apic");
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index a78fdee40c65..c230dd3d09af 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -2377,6 +2377,7 @@ struct _virDomainDef {
virGICVersion gic_version;
char *hyperv_vendor_id;
int apic_eoi;
+ unsigned long long tseg_size;
virDomainClockDef clock;
diff --git a/tests/genericxml2xmlindata/tseg.xml
b/tests/genericxml2xmlindata/tseg.xml
new file mode 100644
index 000000000000..49483f874cd4
--- /dev/null
+++ b/tests/genericxml2xmlindata/tseg.xml
@@ -0,0 +1,23 @@
+<domain type='qemu'>
+ <name>QEMUGuest1</name>
+ <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+ <memory unit='KiB'>219100</memory>
+ <currentMemory unit='KiB'>219100</currentMemory>
+ <vcpu placement='static'>1</vcpu>
+ <os>
+ <type arch='x86_64' machine='q35'>hvm</type>
+ <boot dev='hd'/>
+ </os>
+ <features>
+ <smm state='on'>
+ <tseg unit='MiB'>48</tseg>
+ </smm>
+ </features>
+ <clock offset='utc'/>
+ <on_poweroff>destroy</on_poweroff>
+ <on_reboot>restart</on_reboot>
+ <on_crash>destroy</on_crash>
+ <devices>
+ <emulator>/usr/bin/qemu-system-x86_64</emulator>
+ </devices>
+</domain>
diff --git a/tests/genericxml2xmltest.c b/tests/genericxml2xmltest.c
index d8270a6cae82..daad6e0f78d8 100644
--- a/tests/genericxml2xmltest.c
+++ b/tests/genericxml2xmltest.c
@@ -141,6 +141,8 @@ mymain(void)
DO_TEST_FULL("cachetune-colliding-types", false, true,
TEST_COMPARE_DOM_XML2XML_RESULT_FAIL_PARSE);
+ DO_TEST("tseg");
+
virObjectUnref(caps);
virObjectUnref(xmlopt);
--
2.17.0
--
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