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Re: [Qemu-ppc] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with kvm_vm_check
From: |
Thomas Huth |
Subject: |
Re: [Qemu-ppc] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with kvm_vm_check_extension() |
Date: |
Fri, 15 Sep 2017 07:34:59 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 |
On 14.09.2017 21:25, Greg Kurz wrote:
> 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 <address@hidden>
> ---
> accel/kvm/kvm-all.c | 45 +++++++++++++++++++++++----------------------
> 1 file changed, 23 insertions(+), 22 deletions(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 323c567cfb68..d10534de2da1 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -1533,7 +1533,7 @@ 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;
> }
>
> @@ -1623,27 +1623,6 @@ 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) {
> - fprintf(stderr,
> - "Warning: Number of %s cpus requested (%d) exceeds "
> - "the recommended cpus supported by KVM (%d)\n",
> - 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);
> @@ -1678,6 +1657,28 @@ 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) {
> + fprintf(stderr,
> + "Warning: Number of %s cpus requested (%d) exceeds "
> + "the recommended cpus supported by KVM (%d)\n",
> + 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 =
>
Reviewed-by: Thomas Huth <address@hidden>
- [Qemu-ppc] [PATCH 0/3] kvm: use kvm_vm_check_extension() with VM capabilities, Greg Kurz, 2017/09/14
- [Qemu-ppc] [PATCH 1/3] kvm: check KVM_CAP_SYNC_MMU with kvm_vm_check_extension(), Greg Kurz, 2017/09/14
- [Qemu-ppc] [PATCH 2/3] kvm: check KVM_CAP_NR_VCPUS with kvm_vm_check_extension(), Greg Kurz, 2017/09/14
- [Qemu-ppc] [PATCH 3/3] ppc/kvm: check some capabilities with kvm_vm_check_extension(), Greg Kurz, 2017/09/14
- Re: [Qemu-ppc] [PATCH 3/3] ppc/kvm: check some capabilities with kvm_vm_check_extension(), Greg Kurz, 2017/09/15
- Re: [Qemu-ppc] [PATCH 3/3] ppc/kvm: check some capabilities with kvm_vm_check_extension(), Thomas Huth, 2017/09/15
Re: [Qemu-ppc] [PATCH 3/3] ppc/kvm: check some capabilities with kvm_vm_check_extension(), David Gibson, 2017/09/15