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kvm: check KVM_CAP_NR_VCPUS with kvm_vm_check_extension() 

On a modern server-class ppc host with the following CPU topology:

Architecture:          ppc64le
Byte Order:            Little Endian
CPU(s):                32
On-line CPU(s) list:   0,8,16,24
Off-line CPU(s) list:  1-7,9-15,17-23,25-31
Thread(s) per core:    1

If both KVM PR and KVM HV loaded and we pass:

        -machine pseries,accel=kvm,kvm-type=PR -smp 8

We expect QEMU to warn that this exceeds the number of online CPUs:

Warning: Number of SMP cpus requested (8) exceeds the recommended
 cpus supported by KVM (4)
Warning: Number of hotpluggable cpus requested (8) exceeds the
 recommended cpus supported by KVM (4)

but nothing is printed...

This happens because on ppc the KVM_CAP_NR_VCPUS capability is VM
specific  ndreally depends on the KVM type, but we currently use it
as a global capability. And KVM returns a fallback value based on
KVM HV being present. Maybe KVM on POWER shouldn't presume anything
as long as it doesn't have a VM, but in all cases, we should call
KVM_CREATE_VM first and use KVM_CAP_NR_VCPUS as a VM capability.

This patch hence changes kvm_recommended_vcpus() accordingly and
moves the sanity checking of smp_cpus after the VM creation.

It is okay for the other archs that also implement KVM_CAP_NR_VCPUS,
ie, mips, s390, x86 and arm, because they don't depend on the VM
being created or not.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <150600966286.30533.10909862523552370889.stgit@bahia.lan>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Greg Kurz 2017-09-21 18:01:02 +02:00 committed by Paolo Bonzini
parent 62dd4edaaf
commit 11748ba72e
1 changed files with 22 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
accel/kvm/kvm-all.c
View File

@ -1440,7 +1440,7 @@ static void kvm_irqchip_create(MachineState *machine, KVMState *s)
*/
static int kvm_recommended_vcpus(KVMState *s)
{
int ret = kvm_check_extension(s, KVM_CAP_NR_VCPUS);
int ret = kvm_vm_check_extension(s, KVM_CAP_NR_VCPUS);
return (ret) ? ret : 4;
}
@ -1530,26 +1530,6 @@ static int kvm_init(MachineState *ms)
s->nr_slots = 32;
}
/* check the vcpu limits */
soft_vcpus_limit = kvm_recommended_vcpus(s);
hard_vcpus_limit = kvm_max_vcpus(s);
while (nc->name) {
if (nc->num > soft_vcpus_limit) {
warn_report("Number of %s cpus requested (%d) exceeds "
"the recommended cpus supported by KVM (%d)",
nc->name, nc->num, soft_vcpus_limit);
if (nc->num > hard_vcpus_limit) {
fprintf(stderr, "Number of %s cpus requested (%d) exceeds "
"the maximum cpus supported by KVM (%d)\n",
nc->name, nc->num, hard_vcpus_limit);
exit(1);
}
}
nc++;
}
kvm_type = qemu_opt_get(qemu_get_machine_opts(), "kvm-type");
if (mc->kvm_type) {
type = mc->kvm_type(kvm_type);
@ -1584,6 +1564,27 @@ static int kvm_init(MachineState *ms)
}
s->vmfd = ret;
/* check the vcpu limits */
soft_vcpus_limit = kvm_recommended_vcpus(s);
hard_vcpus_limit = kvm_max_vcpus(s);
while (nc->name) {
if (nc->num > soft_vcpus_limit) {
warn_report("Number of %s cpus requested (%d) exceeds "
"the recommended cpus supported by KVM (%d)",
nc->name, nc->num, soft_vcpus_limit);
if (nc->num > hard_vcpus_limit) {
fprintf(stderr, "Number of %s cpus requested (%d) exceeds "
"the maximum cpus supported by KVM (%d)\n",
nc->name, nc->num, hard_vcpus_limit);
exit(1);
}
}
nc++;
}
missing_cap = kvm_check_extension_list(s, kvm_required_capabilites);
if (!missing_cap) {
missing_cap =