7:55 p.m.
Support for nested KVM is handled via a kernel module configuration
parameters values for kvm_intel, kvm_amd, kvm_hv (PPC), or kvm (s390).
While it's possible to fetch the kmod config values via virKModConfig,
unfortunately that is the static value and we need to get the
current/dynamic value from the kernel file system.
So this patch adds a new API virHostKVMSupportsNesting that will
search the 3 kernel modules to get the nesting value and check if
it is 'Y' (or 'y' just in case) or '1' to return a true/false
whether
the KVM kernel supports nesting.
We need to do this in order to handle cases where adjustments to
the value are made after libvirtd is started to force a refetch of
the latest QEMU capabilities since the correct CPU settings need
to be made for a guest to add the "vmx=on" to/for the guest config.
Signed-off-by: John Ferlan <jferlan(a)redhat.com>
NB to be removed before push - I got data from:
(IBM Z)
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/...
(PPC slide 131)
https://events.linuxfoundation.org/wp-content/uploads/2017/12/Taking-it-t...
Signed-off-by: John Ferlan <jferlan(a)redhat.com>
---
v2: https://www.redhat.com/archives/libvir-list/2018-November/msg00955.html
Changes from code review...
- Rename variables/API's to KVMSupportsNested
- Movement of logic to check/set the 'nested' to inside locations that
ensure KVM was enabled (via capability).
- Change of logic to not use virKModConfig and instead look at the
running kernel value for /sys/module/*/parameters/nested where *
is kvm_intel, kvm_amd, kvm_hv, or kvm
src/qemu/qemu_capabilities.c | 54 ++++++++++++++++++++++++++++++++++++
1 file changed, 54 insertions(+)
diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 20a1a0c201..bef92a679f 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -558,6 +558,7 @@ struct _virQEMUCaps {
virObject parent;
bool usedQMP;
+ bool kvmSupportsNesting;
char *binary;
time_t ctime;
@@ -1530,6 +1531,7 @@ virQEMUCapsPtr virQEMUCapsNewCopy(virQEMUCapsPtr qemuCaps)
return NULL;
ret->usedQMP = qemuCaps->usedQMP;
+ ret->kvmSupportsNesting = qemuCaps->kvmSupportsNesting;
if (VIR_STRDUP(ret->binary, qemuCaps->binary) < 0)
goto error;
@@ -3589,6 +3591,9 @@ virQEMUCapsLoadCache(virArch hostArch,
virQEMUCapsInitHostCPUModel(qemuCaps, hostArch, VIR_DOMAIN_VIRT_KVM);
virQEMUCapsInitHostCPUModel(qemuCaps, hostArch, VIR_DOMAIN_VIRT_QEMU);
+ if (virXPathBoolean("boolean(./kvmSupportsNesting)", ctxt) > 0)
+ qemuCaps->kvmSupportsNesting = true;
+
ret = 0;
cleanup:
VIR_FREE(str);
@@ -3808,6 +3813,9 @@ virQEMUCapsFormatCache(virQEMUCapsPtr qemuCaps)
if (qemuCaps->sevCapabilities)
virQEMUCapsFormatSEVInfo(qemuCaps, &buf);
+ if (qemuCaps->kvmSupportsNesting)
+ virBufferAddLit(&buf, "<kvmSupportsNesting/>\n");
+
virBufferAdjustIndent(&buf, -2);
virBufferAddLit(&buf, "</qemuCaps>\n");
@@ -3848,6 +3856,41 @@ virQEMUCapsSaveFile(void *data,
}
+/* Check the kernel module parameters 'nested' file to determine if enabled
+ *
+ * Intel: 'kvm_intel' uses 'Y'
+ * AMD: 'kvm_amd' uses '1'
+ * PPC64: 'kvm_hv' uses 'Y'
+ * S390: 'kvm' uses '1'
+ */
+static bool
+virQEMUCapsKVMSupportsNesting(void)
+{
+ static char const * const kmod[] = {"kvm_intel", "kvm_amd",
+ "kvm_hv", "kvm"};
+ VIR_AUTOFREE(char *) value = NULL;
+ int rc;
+ size_t i;
+
+ for (i = 0; i < ARRAY_CARDINALITY(kmod); i++) {
+ VIR_FREE(value);
+ rc = virFileReadValueString(&value,
"/sys/module/%s/parameters/nested",
+ kmod[i]);
+ if (rc == -2)
+ continue;
+ if (rc < 0) {
+ virResetLastError();
+ return false;
+ }
+
+ if (value[0] == 'Y' || value[0] == 'y' || value[0] ==
'1')
+ return true;
+ }
+
+ return false;
+}
+
+
static bool
virQEMUCapsIsValid(void *data,
void *privData)
@@ -3856,6 +3899,7 @@ virQEMUCapsIsValid(void *data,
virQEMUCapsCachePrivPtr priv = privData;
bool kvmUsable;
struct stat sb;
+ bool kvmSupportsNesting;
if (!qemuCaps->binary)
return true;
@@ -3933,6 +3977,14 @@ virQEMUCapsIsValid(void *data,
qemuCaps->kernelVersion);
return false;
}
+
+ kvmSupportsNesting = virQEMUCapsKVMSupportsNesting();
+ if (kvmSupportsNesting != qemuCaps->kvmSupportsNesting) {
+ VIR_DEBUG("Outdated capabilities for '%s': kvm kernel nested
"
+ "value changed from %d",
+ qemuCaps->binary, qemuCaps->kvmSupportsNesting);
+ return false;
+ }
}
return true;
@@ -4576,6 +4628,8 @@ virQEMUCapsNewForBinaryInternal(virArch hostArch,
if (VIR_STRDUP(qemuCaps->kernelVersion, kernelVersion) < 0)
goto error;
+
+ qemuCaps->kvmSupportsNesting = virQEMUCapsKVMSupportsNesting();
}
cleanup:
--
2.17.2