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Re: [Qemu-arm] [Qemu-devel] [RFC v3 3/3] ARM: KVM: Check KVM_CAP_ARM_IRQ
From: |
Andrew Jones |
Subject: |
Re: [Qemu-arm] [Qemu-devel] [RFC v3 3/3] ARM: KVM: Check KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 for smp_cpus > 256 |
Date: |
Mon, 16 Sep 2019 16:52:28 +0200 |
User-agent: |
NeoMutt/20180716 |
On Fri, Sep 13, 2019 at 11:56:39AM +0200, Eric Auger wrote:
> Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
> for ARM. The actual capability to instantiate more than 256 vcpus
> was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
> vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
> a single KVM IO device instead of 2.
>
> So let's check this capability when attempting to use more than 256
> vcpus within any ARM kvm accelerated machine.
>
> Signed-off-by: Eric Auger <address@hidden>
>
> ---
>
> v2 -> v3:
> - Implement the check in kvm_arch_init as suggested by Peter
> ---
> target/arm/kvm.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index b10581fa06..b473c63edb 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -182,6 +182,7 @@ int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
>
> int kvm_arch_init(MachineState *ms, KVMState *s)
> {
> + int ret = 0;
> /* For ARM interrupt delivery is always asynchronous,
> * whether we are using an in-kernel VGIC or not.
> */
> @@ -195,7 +196,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>
> cap_has_mp_state = kvm_check_extension(s, KVM_CAP_MP_STATE);
>
> - return 0;
> + if (ms->smp.cpus > 256 &&
> + !kvm_check_extension(s, KVM_CAP_ARM_IRQ_LINE_LAYOUT_2)) {
> + error_report("Using more than 256 vcpus requires a host kernel "
> + "with KVM_CAP_ARM_IRQ_LINE_LAYOUT_2");
> + ret = -EINVAL;
> + }
> +
> + return ret;
> }
>
> unsigned long kvm_arch_vcpu_id(CPUState *cpu)
> --
> 2.20.1
>
>
Reviewed-by: Andrew Jones <address@hidden>